Q!EROU§ FINES: 25¢ pol-day per its RET RN N6 LIBRARY HATER ALS: Place in book return to remove charge from circulation records INTERFERENCE AND CONTROL OF TWO VARIETIES OF JIMSONWEED [DATURA STRAMONIUM L. VAR. STRAMONIUM AND VAR. TATULA (L.) TORR.] IN SOYBEAN [GLYCINE MAX (L.) MERR.] WITH OXYFLUORFEN [2-CHLORO-1-(3-ETHOXY-4-NITROPHENOXY)-4- (TRIFLUOROMETHYL)BENZENE] AND RH 8817 [2-CHLORO-1-(3- CARBOXYETHYL-é-NITROPHENOXY)-4-(TRIFLUOROMETHYL)BENZENE). By Robert Lynn Oakes A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1980 ( .- 1‘ I ‘ L.“ /‘l \ ABSTRACT INTERFERENCE AND CONTROL OF TWO VARIETIES OF JIMSONWEED [DATURA STRAMONIUM L. VAR. STRAMONIUM AND VAR. TATULA (L.) TORR.] IN SOYBEAN [GLYCINE MAX (L.) MERR.] WITH OXYFLUORFEN [2-CHLORO- l-(3-ETHOXY-4-NITROPHENOXY)-4-(TRIFLUOROMETHYL)BENZENE] AND RH 8817 [2-CHLORO-1-(3-CARBOXYETHYL-4-NITROPHENOXY)-4-(TRIFLUOROMETHYL)BENZENE]. By Robert Lynn Oakes Research was conducted to determine: 1) interspecific interfer- ence effects between soybean [Glycine max (L.) Merr.] and each of two varieties of jimsonweed [Datura stramonium L. var. stramonium and var. tatula (L.) Torr.], 2) the efficacy of oxyfluorfen [2-chloro-1-(3- ethoxy-é-nitrophenoxy)-4-(trifluoromethyl)benzene] and RH 8817 [2-chloro- 1-(3-carboxyethyl-4-nitrophenoxy)-4-(trif1uoromethy1)benzene] on two varieties of jimsonweed and subsequent injury to soybean, 3) the in— fluence of soil organic matter content and temperature on the preemer- gence activity of oxyfluorfen and RH 8817 and the effects of soil mois- ture and organic matter content on activity due to volatilization, and 4) translocation and metabolism differences between oxyfluorfen and RH 8817. Interference studies indicated that at a population density of 4.4 pl/mz, var. tatula and var. stramonium reduced soybean yield by 58% and 46%, respectively, and both varieties at this population density Robert Lynn Oakes reduced soybean dry matter accumulation by 462. Both jimsonweed vari- eties, at a population density of 8.8 pl/mz, reduced soybean flowers, pods, and nodes per plant by 45%, 41%, and 41%, respectively. A natural stand of var. tatula, at a population density of 0.7 pl/mz, reduced soybean yield by 22%. Variety tatula was found to accumulate 2.5 times more dry matter than var. stramonium at a population density of 17.6 p1/m2. Variety tatula was observed to overtop the soybean canopy while var. stramonium had a highly branched, shorter growth habit producing more fruit per unit dry weight than var. tatula. Replacement series studies with five population density ratios of soybean and each variety of jimsonweed indicated interference was not mediated by an allelochemic intermediate. Field studies indicated oxyfluorfen at 1.12 kg/ha required the addition of 2.24 kg/ha of alachlor [2-chloro-2',6'-diethy1-N-(methoxy— methyl)acetanilide] or 0.56 kg/ha of metribuzin [4-amino-6ftgrgrbutyl- 3(methylthio)fiasftriazin-5(4§)-one] when shallowly incorporated, for season-long control of both jimsonweed varieties. RH 8817 was effec- tive when applied alone at 1.12 or 1.40 kg/ha or in combination with- alachlor at 2.24 kg/ha or metribuzin at 0.56 kg/ha. Activity of both diphenylether herbicides was greater on lower organic matter content soils and when applied preemergence rather than shallowly incorporated to a depth of 1.25 cm. Injury to soybean hypocotyls though was greater under these conditions and also when environmental conditions following emergence slowed soybean growth rates. Visual injury to soybean plants usually occurred from diphenylether herbicide treatments, often reducing population densities but generally not reducing soybean yields. Robert Lynn Oakes Greenhouse studies indicated that on greenhouse mix soil with 15% organic matter content, metribuzin was 1.9 times more active than either oxyfluorfen or RH 8817 and 11.8 times more active than alachlor or metolachlor [4-amino-6ftggtfbutyl-3(methylthio)fggftriazin-5(4§)one] on both varieties of jimsonweed. No significantly different responses were found between both jimsonweed varieties for any individual herbi— cide treatment. RH 8817 activity on var. tatula was 20% to 40% lower than oxyfluorfen on 5.5% organic matter content soil but on 1.5% and 8.2% organic matter content soils, no difference in activity was found between either herbicide. Injury to both soybean and var. tatula was found from vapors from treated soil and was greater from oxyfluorfen than from RH 8817. Injury was greatest from herbicide vapors on soil with low organic matter content and when soils were moist. Soybean hypocotyl injury was found to increase as day—night temperatures and soil organic matter content decreased and was greater from oxyfluorfen than from RH 8817. Translocation and metabolism studies indicated that 1 day after treatment, 7.6% of both 14C-RH 8817 and 14C-oxyfluorfen was moved ac— ropetally from hypocotyl applications to soybean while 7.04% and 6.66% of each herbicide, respectively, were translocated acropetally in var. tatula. Metabolism of RH 8817 was from 3.2% to 18.3% greater than oxy- fluorfen in soybean hypocotyls after 1 and 12 days, respectively. After 3 and 6 days, no differences in metabolism of either 14 C-herbicide was found in var. tatula. Radioactivity in the hexane-soluble fraction of the hypocotyl was identified as each respective parent herbicide applied in both plant species. For Cher, whom I love with all of my heart, may our lives continue to be filled with His love and directed to fulfill His purposes. For my man and dad, whom I love and am grateful for their con- fidence in my ability to attain my best. For the Lord Jesus Christ, "whom have I in heaven but Thee and there is nothing upon earth that I desire besides Thee" (Psalms 73:24). 11 ACKNOWLEDGEMENTS The author wishes to express his heart-felt thanks to his major professor, Dr. William F. Meggitt, for his exhortations and encouragements throughout this project and especially his willingness to allow me the opportunity to be involved in the weed control program at Michigan State University. Special appreciation is extended to Dr. Donald Penner for his careful insights and suggestions in conducting this research and for his careful critique of this manuscript. The additional thoughts and comments offered by Drs. Alan Putnam and Matthew Zabik are also gratefully appreciated. The author wishes to express a special thanks to Ms. Mollie Stark and Ms. Barbara Saunders without whose help this research would never have been completed as accurately or promptly. A special thanks is extended to my wife whose able typing and keen eye for grammatical correctness was invaluable. iii TABLE OF INTRODUCTION . . . . . . . . CHAPTER 1. REVIEW OF LITERATURE . JIMSONWEED . . . . . . . Historical Background Toxicity and Uses Biology . . . . . . Distribution . . . . Problem Weed . . . . Herbicide Control DIPHENYLETHER HERBICIDES Light Activation . . Persistence in Soil Absorption and Translocation . Metabolism . . . MOde of Action . Selectivity . . . . LITERATURE CITED . . . . CHAPTER 2. INTERFERENCE BY DATURA CONTENTS STRAMONIUM L. VAR. STRAMONIUM AND DATURA STRAMONIUM L. SOYBEAN [GLYCINE MAX (L.) MERR.] . ABSTRACT O O O O O O O 0 INTRODUCTION . . . . . . MATERIALS AND METHODS . . RESULTS AND DISCUSSION . LITERATURE CITED . . . . iv VAR. TATULA (L.) .11 .13 .13 .15 .17 .20 .24 .27 .29 IN .39 Page CHAPTER 3. EFFICACY 0F OXYFLUORFEN AND RH 8817 ON TWO VARIETIES 0F JIMSONWEED [DATURA STRAMONIUM L. VAR. STRAMONIUM AND VAR. TATULA (L.) TORR.] IN SOYBEAN [GLYCINE MAX (L.) MERR.] . . . . . . . . . . . . . . . . . . . . . . . . . . .61 ABSTRACT . . . . . . . . . . . . . . . . . . . . . . .61 INTRODUCTION . . . . . . . . . . . . . . . . . . . . .63 MATERIALS AND METHODS . . . . . . . . . . . . . . . . .64 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . .66 LITERATURE CITED . . . . ... . . . . . . . . . . . . .70 CHAPTER 4. RELATIVE RESPONSES OF TWO VARIETIES OF JIMSONWEED (DATURA STRAMONIUM L.) AND SOYBEAN [GLYCINE MAX (L.) MERR] TO PREEMERGENCE APPLICATIONS OF OXYFLUORFEN AND RH 8817 O O I I O O O O O O O O O O O I O O O O O O O O O .78 ABSTRACT . . . . . . . . . . . . . . . . . . . . . . .79 INTRODUCTION . . . . . . . . . . . . .'. . . . . . . .80 MATERIALS AND METHODS . . . . . . . . . . . . . . . . .81 Cultural Practices - Greenhouse . . . . . . . . .81 Differential Response of Jimsonweed Varieties . .81 Role of Soil Organic Matter Content . . . . . . .82 Activity of Herbicide Vapors from Soil . . . . . .82 Soybean Hypocotyl Injury from Diphenylether Herbicides . . . . . . . . . . . . . . . . . . . .83 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . .84 Differential Response of Jimsonweed Varieties . .84 Role of Soil Organic Matter Content . . . . . . .85 Activity of Herbicide Vapors from Soil . . . . . .86 Soybean Hypocotyl Injury from Diphenylether Herbicides . . . . . . . . . . . . . . . . . . .88 LITERATURE CITED 0 O O O O I O O O O O O O O O O O O O 90 14 14 Page CHAPTER 5. FATE OF C-RH 8817 AND C-OXYFLUORFEN FROM HYPOCOTYL APPLICATIONS TO SOYBEAN [GLYCINE MAX (L.) MERR. 'HAROSOY 63'] AND JIMSONWEED [DATURA STRAMONIUM L. VAR. TATUI-A (L.) TORRO] O O O C C C I O C O O C I O O O O O O O 109 ABSTRACT . . . . . . . . . . . . . . . . . . . . . . 109 INTRODUCTION . . . . . . . . . . . . . . . . . . . . 111 MATERIALS AND METHODS . . . . . . . . . . . . . . . . 112 Cultural Practices . . . . . . . . . . . . . . . 112 14C-Herbicide Application . . . . . . . . . . . 112 Sample Handling and Extraction Procedures . . . 112 Thin Layer Chromatography . . . . . . . . . . . 113 Statistical Considerations . . . . . . . . . . . 114 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 114 Translocation and Metabolism in Soybean . . . . 114 Translocation and Metabolism in var. tatula . . 116 LITERATURE CITED . . . . . . . . . . . . . . . . . . 117 APPENDICES O O O O O O I O O O O O O O O O O O O O O O O O 124 BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . 127 vi Table LIST OF TABLES CHAPTER 1 Page World distribution and ranking as a weed problem of Datura stramonium L. var. chalybaea Koch (Syn. Q. tatula L.) I O O C C O O O O O O O O I O O O O O O O O 34 CHAPTER 3 Physical and chemical analysis of soils from 5 field locations used in herbicide trials . . . . . . . . . .71 Temperature and precipitation data for Location III, V, and IV, 7 days preceding and 14 days following soybean planting on May 23, 27, and 28, respectively .72 Temperature and precipitation data for Location I, 7 days preceding and 14 days following soybean planting on June 25, 1980 . . . . . . . . . . . . . .73 Effect of shallow incorporation treatments of oxyfluorfen or RH 8817 applied alone or in combination with alachlor or metribuzin on Datura stramonium L. var. stramonium and soybean. Planting occurred on May 28, 1980 at Location IV on Owosso sandy clay loam soil with 3.5% organic matter content. . . . . . . . . . . . . .74 Effect of shallow incorporation treatments of oxyfluorfen or RH 8817 applied alone or in combination with alachlor or metribuzin on Datura stramonium L. var. stramonium and soybean. Planting occurred on May 23, 1980 at Location III on Parkhill clay loam soil with 5.5% organic matter content . . . . . . . . . . . . .75 Effect of shallow incorporation or preemergence treatments of oxyfluorfen or RH 8817 on a mixture of two varieties of Datura stramonium L. Planting occurred on May 27, 1980 at Location V on Capac sandy clay soil with 3.7% organic matter content . . . . . .76 Effect of shallow incorporation or preemergence treatments of oxyfluorfen or RH 8817 applied alone or in combination with alachlor or metribuzin on Datura stramonium L. var. tatula (L.) Torr. and soybean. Planting occurred on June 25, 1980 at Location I on Selfridge sandy loam soil with 4.2% organic matter content . . . . . . . . . . . . . . . . . . . . . . .77 vii Table CHAPTER 4 Page Physical and chemical analysis of soils used in greenhouse and growth chamber experiments . . . . . .91 GRSO values (kg/ha) for preemergence applications of selected herbicides on Datura stramonium L. var. tatula (L.) Torr. and Datura stramonium L. var. stramonium based on visual injury . . . . . . . . . .92 CHAPTER 5 14 14 Translocation and metabolism of C-RH 8817 and C- oxyfluorfen l, 3, 6, and 12 days after application to soybean hypocotyls. Translocation and metabolism of 14C-RH 8817 and 14C- oxyfluorfen 3 and 6 days after application to hypo- cotyls of Datura stramonium L. var. tatula (L.) Torr seedlings . . . . . . . . . . . . . . . . . . . . . 119 viii Figure 5A 5B LIST OF FIGURES CHAPTER 1 Page Structures of diphenylether herbicides . . . . . . . 36 Proposed metabolic pathway of fluorodifen degrada- tion in peanut roots by Shimabukuro eg 31. . . . . . 38 CHAPTER 2 Soybean dry matter production (g/mz) as affected by population densities of 4.4, 8.8, and 17.6 pl/m2 of either Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. . . . . . . . . 50 Soybean seed production (g/mz) as affected by popula- tion densities of 4.4, 8.8, and 17.6 p1/m2 of either Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. . . . . . . . . 52 Dry matter production of Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. at population densities of 4.4, 8.8, and 17.6 p1/m2 when grown with soybean at a population density of 17.6 pl/mz. . . . . . . . . . . . . . . . 54 Seed production of Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. at population densities of 4.4, 8.8, and 17.6 p1/m2 when grown with soybean at a population density of 17.6 p1/m2. . . . . . . . . . . . . . . . . . . . 56 Replacement series responses to population density mixtures of soybean and Datura stramonium L. var. stramonium measured as dry matter accumulation (g/mz) of both plant species as compared with a hypothetical model . . . . . . . . . . . . . . . . . 58 Replacement series responses to population density mixtures of soybean and Datura stramonium L. var. tatula (L.) Torr. measured as dry matter accumula- tion (g/mz) of both plant species as compared with a hypothetical model . . . . . . . . . . . . . . . . . 60 ix Figure 1 CHAPTER 4 Page Drawing of potting system used to measure injury to soybean and jimsonweed from vapors of oxyfluorfen and RH 8817 treated 8011 O O O O O I O O O O O O O O O 94 Percent visual injury of Datura stramonium L. var. tatula (L.) Torr. from preemergence applications of oxyfluorfen on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% 0M, and Capac sandy clay loam soil with 8.2% 0M . . . . . . .96 Percent visual injury to Datura stramonium L. var. tatula (L.) Torr. from preemergence applications of RH 8817 on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% OM, and Capac sandy clay loam soil with 8.2% 0M. . . . . . . .98 Comparison of the visual injury to Datura stramonium L. var. tatula (L.) Torr. from preemergence applica- tions of oxyfluorfen and RH 8817 on Selfridge clay loam soil with 5.5% OM . . . . . . . . . . . . . . . 100 Comparison of the visual injury to Datura stramonium L. var. tatula (L.) Torr. from vapors of oxyfluorfen and RH 8817 from preemergence applications to sandy clay loam soils with either 1.5% or 8.2% organic matter contents and which were brought to field capacity once daily . . . . . . . . . . . . . . . . 102 Comparison of the visual injury to soybean [Glycine ‘93! (L.) Merr.] from vapors of oxyfluorfen and RH 8817 from preemergence applications to sandy clay loam soils with either 1.5% or 8.2% organic matter contents and which were brought to field capacity once daily . . . . . . . . . . . . . . . . . . . . . 104 Visual injury ratings for soybean hypocotyls following preemergence applications of oxyfluorfen on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% 0M, and Capac sandy clay loam soil with 8.2% 0M . . . . . . . . . 106 Visual injury ratings for soybean hypocotyls following preemergence applications of RH 8817 on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% 0M, and Capac sandy clay loam soil with 8.2% 0M . . . . . . . . . 108 Figure 1 CHAPTER 5 Page Radioscans of thin-layer chromatograms from the hexane-soluble fraction from soybean hypocotyl l and 12 days after application of 14C-RH 8817 . . . 121 Radioscans of thin-layer chromatograms from the hexane-soluble fraction from soybean hypocotyl l and 12 days after application of 14C-oxyfluorfen . 123 xi Appendix LIST OF APPENDICES Page Effect of shallow incorporation treatments of oxyfluorfen or RH 8817 applied alone or in combination with alachlor or metribuzin on Datura stramonium L. var. tatula (L.) Torr. Planting occurred on June 28, 1980 at Location II on Whitaker sandy clay loam soil with 4.1% organic matter content. . . . . . . . . . . . . 124 Concentration of 14C-RH 8817 (10.11 uCi/mg) and 14C-oxyfluorfen (2.61 uCi/mg) in various plant sections following hypocotyl application of 1 mg per plant of each herbicide after 1, 3, 6, and 12 days. . . . . . . . . . . . . . 125 Concentration of 14C-RH 8817 (10.11 uCi/mg) and 14C-oxyfluorfen (2.61 uCi/mg) in various plant sections following hypocotyl application of 0.25 mg per plant of each herbicide after 3 and 6 days. . . . . . . . . . . . . . . . . . 126 xii INTRODUCTION Jimsonweed is among the worst broadleaf weeds in the world in soybean and is becoming an increasing problem in Michigan. When jim- sonweed is present in soybean fields, it not only reduces yield but also increases the difficulty of harvest and can contaminate the soy- bean seed with jimsonweed seeds which contain toxic alkaloids. Few preemergence herbicides are active on jimsonweed and those which are produce inconsistent control and usually injure soybean when used at rates which are high enough to be efficaceous. In the early 1960's, nitrofen (2,4-dichloropheny1-p-nitropheny1 ether) was intro- duced by Rohm and Haas Company for preemergence and postemergence weed control in rice (Oryza sativa L.). Recently developed diphenylether herbicides have been found to be selective in soybean for preemergence control of many annual broadleaf weeds and certain annual grasses. Oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trif1uoromethyl) benzene] and RH 8817 [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoro- methy1)benzene] are new diphenylether herbicides which may be effective in controlling both varieties of jimsonweed in soybean. Research has therefore been conducted to determine any differen- tial interspecific interference between soybean and each jimsonweed variety. Studies were also conducted to determine the relative effec- tiveness of oxyfluorfen and RH 8817 in field and greenhouse studies on both varieties of jimsonweed and to determine the factors affecting their injury to soybean. Radioactive studies were performed to assess the role of translocation and metabolism as a basis for selectivity between soybean and jimsonweed and as a basis of differential sensi- tivity between oxyfluorfen and RH 8817 on both plant species. CHAPTER 1 REVIEW OF LITERATURE JIMSONWEED Historical Background The genus Datura has been known from antiquity being noted in early Sanscrit, Chinese and Arabian writings for its hallucinogenic properties. Buddists believed this property was imparted to the plant as rain or dew drops which fell upon the plant each time Buddha preached in heaven (2). In India and Africa it has been smoked with Cannabis preparations for its narcotic properties. Algonquin Indians used it in initiation rights for manhood and Zuni Indians of the Southwest used it as an anesthetic, an ointment for wounds and bruises and by rain priests to intercede with the gods. Mexican Indians cur- rently and prior to Cortez's conquest have used it for ceremonial vi- sions and by medicine men to help diagnose diseases (51). Wide usage was recorded in medieval Europe where it was ingested, sniffed, smoked or rubbed onto the skin in ointments of oil or fat. Accounts of its use have been reported by Porta, a colleague of Galileo, used by Castaneda, the Mexican apprentice of Don Juan and as the poison taken by Shakespeare's Juliet (35, 50). In 1676 British troops were sent to Jamestown colony to quell Bacon's rebellion and as recorded by Beverley (4), discovered unknow- ingly the unusual properties of this plant. The James—Town Weed, which resembles the Thorny Apple of Peru,. . .is supposed to be one of the greatest Coolers in the world. This being an early plant, was gathered very young for a boiled salad, by some of the soldiers. . .and some of them ate plentifully of it, the effect of which was a very pleasant comedy; for they turned natural fools upon it for several days: One would blow up a feather in the air; another would dart straws at it with much fury; and another stark naked was sitting up in a corner, like a monkey, grin- ning and making mows at them; with a countenance more antick, than any in a Dutch Droll. In this frantick condition they were confined, lest they should in their folly destroy them- selves; though it was observed that all their actions were full of innocence and good nature. Indeed, they were not very cleanly; for they would have wallow'd in their own ex- crements, if they had not been prevented. A thousand such simple tricks they play'd, and after eleven days, return'd to themselves again, not remembering anything that had pass'd. Taxonomically the genus name Datura was first used by Linnaeus (1737) in his Hortus Cliffortianus (56) and was either a Latinization of an East Indian name Dhatura or Dutra or from the Arabic name Tatorah. Linnaeus later used the specific epithets of stramonium and tatula in his Species Planatarium (56) to separate plants with white flowers from those with purple flowers, respectively. Later research by Bateson and Saunders (3) found these plants to differ only by a single pair of genes for pigment color, the gene for the purple form being dominant. Currently these plants are regarded as varieties and were taxonomically separated by Torrey in 1824 as Datura stramonium L. var. stramonium (green stem, white flower) and Datura stramonium L. var. tatula (L.) Torr. (purple stem, pinkish-purple flower) (23). Toxicity and Uses The alkaloids hyosycamine, atropine, and scopolamine are present in all plant parts and have been reported to produce symptoms of thirst, pupil dilation, dry mouth, dermatitis, headache, hallucinations, nausea, rapid pulse, temperature elevation, high blood pressure, delirium, convulsions, coma, and death. Amounts as small as 4-5 g of leaves or seeds have been fatal to children (25). The U.S. Department of Agriculture reported in 1897 that 5 children were badly poisoned in Alpena, Michigan by eating the seeds and in a separate incident that same year in a city park in New York, 3 children were poisoned, one of whom died, from ingestion of seeds (8). Cattle have frequently been poisoned by eating the weed mixed with hay and 285 to 400 g of the green plant have been shown to be fatal (15). Mikolich g£_al, (43) reported in 1975 that ten patients suffered from acute anticholin— ergic secondary syndrome from ingestion of jimsonweed seeds. Six of the patients suffered hyperpyrexia and severe neurologic derangement. Electroencepholographs resulted in bizarre rhythmical bursts and slow wave activity accompanied by several other diagnostic symptoms. Scopolamine, which has been shown to be the alkaloid producing hallucinogenic responses, has been used by physicians as a preanesthe— tic in childbirth, surgery and ophthalmology (9). Inhalation of the smoke from burning jimsonweed has been used by asthma victims and was a more effective cough medicine than opium. Herbalists have applied it externally in times past for burns, scalds and inflammations. At one time Datura stramonium L. var. stramonium was extensively cultivated in Hungary for these medicinal properties. The nineteenth century Spanish Cigarette Company of London and New York produced herbal cig— arettes from a mixture of tobacco and leaves of Datura stramonium L. and made the following advertising appeal: Spanish Herbal Cigarettes when smoked emit an agreeable and fragrant odor, soothing and pleasant, and leave no objection- able after-effect upon the palate. They are quite free from all ingredients of an injurious or undesirable character, and in cases of Coughs, Colds, Bronchitis, Asthma and Pulmonary Complaints, generally they will be found of the greatest value and benefit (4). Biology Information about the life cycle of weeds, growth rate, environ- mental influences, plant to plant interactions and many other factors have proven useful in establishing optimal control programs for vari- ous weeds. Holm and Miller (29) investigated germination responses of 11 weed species to chemical and physical treatments designed to break dormancy and stimulate germination. Jimsonweed seed placed in petri dishes with 1% water agar at 23 C in the dark had a 12% germin- ation rate which was increased to 36% in the presence of 10-2M of gib— berellic acid (GA3) and 10-3M of thiourea, but kinetin, 2—chloroethy1- phosphoric acid (CEPA) and naphthaleneacetic acid (NAA) had no effect while abscisic acid (ABA) at 10-5M inhibited germination completely. Physical treatments of increased temperature (30-90 C at 5 C intervals), sonication, immersion in liquid N2, and infrared light exposure had no promotive effect on germination. Hormonal control of germination in 10 weed species was also examined by Holm and Miller (30). Freshly harvested jimsonweed seeds were found to have stimulated germination in the light (26%) versus the dark (15%). Seeds were buried in the field at a depth of 7.5 cm from February to August to determine if light was required in natural systems and it was found that seeds be- came absolutely dependent on light for germination (10 vs 0%). Re- sponse to 1 h and 2 h red light followed by 4 h far-red light complete- ly inhibited germination and 10-4 GA gave the same response as l h 3 of red light. These results indicated a phytochrome sensitive mechanism was operative in promotion of germination. Stoller and Wax (58) found that jimsonweed was one of several weed species whose seeds underwent an afterripening response with time stored in the lab which increased their germination. Their work showed light was necessary to increase germination thus also indicating the involvement of a phytochrome sensitive system in promotion of germination. A seed burial test showed a decrease in viability over time due to decomposition with an increase in seed survival with depth of burial. The Duval seed-burial experiment reported by Toole and Brown (60) demonstrated that 91% of the jimsonweed seed buried at a depth of 34 cm germinated after 39 years. Periodicity of germination of 6 weed species was examined by Stoller and Wax (57) who found that jimsonweed displayed several spor- adic flushes of seedlings after May 1 and was correlated with rainfall which brought the upper 10 cm to field capacity. Cummulative heat units were not correlated with the initial emergence of seedlings. Seedling flushes of jimsonweed were preceded by at least 1.0 cm of rainfall and occurred with equal frequency from seeds at 2.5 and 5.1 cm depths. No seeds emerged from a depth of 15.2 cm and only 3% from 10.2 cm although 22% of the jimsonweed seeds recovered from these depths still germinated upon recovery. Seedlings emerged as early as April 20 with a major flush as late as July 20. Frazee and Stoller (20) examined the differential growth responses of seven dicotyledonous weeds, corn (Zg§_may§ L.), and soybean [Glycine ‘mgx (L.) Merr.] in growth chambers and field plots. They found the optimum growth of jimsonweed occurred during 24 C-day and 18 C-night and that higher temperatures produced only a slight increase in growth rate as measured by plant height. Field studies indicated that jim- sonweed emerged around May 1 and had an intermediate plant height com— pared to other species tested. In growth chamber studies, jimsonweed had the lowest cumulative growth rate under a temperature regime of 30 C-day and 24 C-night. The influence of several environmental factors on jimsonweed growth and development was studied by Smith and Rahn (53) who found that plants grown under 12 h days produced flowers in 32 days and fruit in 72 days and when grown under 16 h days produced flowers in 37 days but yielded no fruit. When grown in 27% shade, plants produced more dry weight than in other lighting regimes. In a fertility study, plants were responsive to additional phosphorous but not to addition of nitro- gen, potassium or a combination of all three nutrients. Examination of the depth of germination showed seedlings emerged from 15.2 cm but not from depths of 17.8 cm or greater with 0 to 7.6 cm being optimal. Buchanan gt a1. (6) found in an examination of warm-season and cool-season weed species grown on fine sandy loam at pH levels rang- ing from 4.7 to 6.3, jimsonweed had low to medium tolerance on low pH soils. In greenhouse and long-term field studies by Hoveland g£_al, (33), jimsonweed was found to be responsive to increased soil phosphor— ous and potassium levels. Severe stunting occurred when plants were grown on phosphorous or potassium deficient soils. Agaev (1) found in intraspecific competition among annual plants that jimsonweed responded to increased population densities with a reduced development rate (negative crowding effect). Distribution In a recent examination of the world's literature on weeds and weed science and in visits to most countries of the world, a team of researchers (27) found fewer than 8000 species behave as weeds in ag— riculture and only 250 of these were important to world agriculture. This thorough treatment of world weeds requested weed scientists in each of 124 countries to rank the weeds of importance in their country. Rankings consisted of: Serious Weed: ranks among the 2 or 3 most serious weeds in a crop. Principle Weed: ranks among the five most serious weeds in a crop. Common Weed: very widespread in many crops requiring constant effort to control. Present: a weed but of unknown rank. Flora: present but no evidence it is a weed. Datura stramonium L. var. chalybaea Koch (Syn. Q. tatula L.) (Table 1) was ranked among these 250 most significant weeds and was determined to be a Serious Weed in 13 countries on 4 continents, a Principal Weed in 5 countries on 4 continents, a Common Weed in 15 countries on 3 continents and a weed of unknown rank in 31 countries on every continent of the world. This wide distribution geographically, climatically and agriculturally points to this plant's tenacity to sur- vive and to compete in numerous crops and environments and to its cur- rent and future potential as a weed. Problem Weed Jimsonweed was listed in The World's Worst Weeds by Holm g£.al. (28) as one of the 8 most important broad-leaved weeds in soybeans, a list which did not include other problem weeds such as velvetleaf (Abutilon theophrasti Medic.) or cocklebur (Xanthium pensylvanicum 10 Wallr.). Jimsonweed is widely distributed as a weed throughout the United States with the exception of the northern half of the Great Lake states and the northwest and mountain states (61). In the last 'evaluation by the Agricultural Research Service in 1972 of the extent and cost of control of important weeds, jimsonweed was not ranked among 25 weeds most frequently reported as problems in the 13 agronomic crops surveyed (62). Jimsonweed was ranked, though, among the 5 most impor- tant weeds in soybean in Delaware, Maryland, New Jersey, North Carolina, Virginia, Indiana and Michigan which were found to have from 15 to 50% of the soybean acreage infested. A total of 1.35 million of the 40.7 million acres of soybean harvested were infested but this was only 10% of the acreage infested with velvetleaf. The only other agronomic crop in which jimsonweed was reported among the 5 most important weeds was corn in Delaware and California. Minor crops in which jimsonweed was listed as one of the five most important weeds include sweet corn in Ohio, potato (Solanum tuberosum L.) in Delaware and Illinois, and solanaceous fruits in Delaware, Maryland and Indiana. A 1974 survey of weed problems in Illinois (41) reported jimson- weed was the Sth most difficult annual broadleaf weed to control in corn and soybean and had increased significantly in severity in the previous 5 years. It was reported as a problem weed in 88 of the 107 counties in the state and was listed among the top four annual broad- leaf weeds in soybean in 6 of the 10 extension districts and in corn in 4 of 10 extension districts. The 1979 extension county agent weed survey of annual grasses, annual broadleaves and perennial weeds in Indiana prepared by Jordan (33) listed jimsonweed as the 5th most 11 common weed of agronomic crops and the 9th most difficult to control. Distribution by counties showed it was the 4th most common weed in the east and southeast counties and the 3rd most common in the north- west and north central counties. Ohio has reported a significant prob- lem with jimsonweed in 25% of the soybean acreage and jimsonweed was ranked the 5th most prevalent broadleaf weed (59). In Michigan, jim- sonweed was found to be one of the three special problem weeds in terms of difficulty of control in soybean (42). In a 1980 survey conducted in 13 states by the Southern Weed Science Society of America, jimsonweed was ranked in Tennessee as the 9th most common weed in both cotton (Gossypium hirsutum L.) and tobacco (Nicotiana tobacum L.) and the 10th most troublesome weed in tobacco (55). South Carolina and Virginia ranked jimsonweed among 27 impor— tant weeds in peanut (Arachis hypogaea L.) and Virginia also listed it as an important weed in tobacco. Jimsonweed was not ranked among the ten most troublesome or common weeds in corn, peanut, sorghum [Sorghum bicolor (L.) Moench], soybean, haycrops, sugarcane (Saccharum officinarum L.), fruits, vegetables, right-of—ways, or rangelands. Herbicide Control Few preemergence or preplant incorporated herbicides produce ef- fective season-long control of jimsonweed with adequate soybean toler- ance. Parochetti (45) found control of early but not late germinating jimsonweed when 3.36 kg/ha of fluorodifen (p-nitrophenyl-u,a,o-trifluoro- 2—nitro-p-toly1 ether) was applied to soybean at cracking stage. Vernolate (§7propy1 dipropyl thiocarbamate) applied preplant incorpor— ated at 3.36 kg/ha also controlled early germinating seedlings. Wax 12 (66) found that metribuzin [4-amino-6-tgggfbutyl-3(methylthio)j§§r triazin-5(4H)one] at 0.56 to 0.84 kg/ha resulted in 85% to 95% control of jimsonweed if abundant rainfall occurred within 10 days after treat- ment. Control was inadequate under limited rainfall unless incorpor- ated at least 5.1 cm. Naptalam (Eel-naphythylphthalamic acid) and dinoseb (2fgggfbutyl—4,6-dinitrophenol) at 3.36 and 1.68 kg/ha, respec- tively, applied to soybean at cracking stage was reported by Parochetti (45) to control 93% of early and 99% of late germinating seedlings. Sommerville and Wax (54) found control of jimsonweed with chloramben (3-amino-2,5-dichlorobenzoic acid) was ineffective at both 1.7 and 2.4 kg/ha regardless of the depth of incorporation. Field experiments conducted by French and Santelmann (22) with oxyfluorfen [2-chloro-1- (3-ethoxy-4-nitrophenoxy)-4—(trifluoromethyl)benzene] showed 0.56 kg/ha provided excellent control of jimsonweed with little or no injury to cotton, peanut, and soybean at rates up to 1.12 kg/ha. Yih and Swithenbank (67) found preemergence applications of oxyfluorfen at 0.25 kg/ha gave 95% control of jimsonweed, whereas nitrofen (2,4- dichlorophenyl p-nitrophenyl ether) at 4.0 kg/ha gave 50%, and fluoro- difen at 4.0 kg/ha gave no control. Post emergence control with bentazon [3-isopropyl—1Hf2,l,3- benzothiadiazin-4(3H)-one 2,2-dioxide] was examined by Parochetti (45) who found 95% control when 0.84 or 1.68 kg/ha were applied to jimsonweed 5.1 to 7.6 cm high or 1.68 kg/ha to jimsonweed 12.7 to 15.2 cm high._ Mathis and Oliver (38) reported 1.12 kg/ha gave 100% control 1 week after emergence and 93% control when plants were 4 weeks old. Johnson 33 a1. (32) reported 0.28 kg/ha of acifluorfen (sodium 5-[2-chloro-4- (trifluoromethyl)phenoxy]-2 nitrobenzoate) gave 90% control and 0.56 13 kg/ha produced 95% control. Soybean showed good tolerance although temporary leaf cupping, crinkling and speckling appeared on treated foliage following application. Soybean at all stages of growth were tolerant. Mangeot (37) found acifluorfen applied at 0.6 kg/ha pro- duced 83% to 99% control of jimsonweed in soybean. No reduction in soybean yield resulted even when acifluorfen was applied at 2.2 kg/ha though visual injury was rated as 21% DIPHENYLETHER HERBICIDES Nitrofen was the first diphenylether herbicide commercially devel- oped in the early 1960's and was used in Japan for effective preemer- gence control of barnyardgrass (Echinochloa crusgalli Beauv.) in trans- planted rice (Oryga sativa L.). Until its recent withdrawal from the market, nitrofen was among the most important herbicides registered for weed control in numerous vegetable crops. Diphenylether herbicides are currently registered for use in agronomic crops such as corn, cotton, peanut, pea (Pisium sativum L.), potato, soybean, sunflower (Helianthus annus L.) and wheat (Triticum aesticum L.) showing activity on several annual broadleaf weeds normally tolerant to other preemergence herbi- cides (68). Current efforts in directed synthesis of new diphenylether herbicides are underway to increase their activity on specific hard to control weeds and reduce crop injury by selective placement of substit- uent groups on the p-nitrodiphenylether backbone (Figure 1). Light Activation All currently registered diphenylether herbicides contain a struc- tural backbone of p-nitrodiphenylether to which substituent groups are added at the ortho and para positions of the benzene ring and at the 14 meta position of the nitrophenol ring and oriented cis to any ortho group on the benzene ring. 0f 10 diphenylether herbicides examined by Matsunaka (39), those with ortho-substituents on the benzene ring were found to require light for activity whereas non-ortho-substituted compounds had no light requirement. Studies with rice demonstrated that illumination of a nitrofen solution prior to application did not injure subsequently treated rice plants when placed in the dark after treatment. The presence of known Hill reaction inhibitors had no af- fect on the activity of nitrofen which indicated direct inhibition of photosynthesis was not the mode of action. Experiments with arti- ficial and natural albino rice mutants by Matsunaka (40) found these plants to be tolerant to nitrofen in the light whereas yellow rice mutants were susceptible. The major component of pigments in yellow mutants was xanthophyll which could have been responsible for photo- activation of nitrofen. Work by Vanstone and Stobbe (64) with oxyfluor- fen on buckwheat (Faggpyrum esculentum Moench. 'Tokyo') showed plants placed in the dark for 4 days following treatment were not injured un- til they were moved to the light. Light wavelengths of 565 nm to 615 nm and increased light intensity were both effective in producing in— jury. Photosynthesis apparently was not affected directly but only after loss of membrane integrity. In research by Fadayomi and Warren (16) with nitrofen and oxyfluorfen, postemergence applications to green- 'bean (Phaseolus vulgaris L. 'Spartan Arrow') were made to plants either pre-treated with 24 h of darkness or maintained in the light before treatment. Both pre-treatments resulted in injured plants when placed in the light after treatment. This indicated recently produced photo- synthate prior to treatment was not involved in photoactivation. Fresh 15 weights of treated plants were not lower than the control when they remained in the light for 8 h followed by removal to darkness although injury symptoms were visible after only 4 h in the light. Plants placed in the dark for 24 h immediately following spraying and then transferred to the light for 3 days showed less injury than those with no dark treatment. The light response of greenbean and soybean to preemergence treat- ments of fluorodifen was examined by Pollak and Crabtree (48) who found that dry weight reduction from 3.4 kg/ha decreased with increasing light intensities from 5 to 22 klux. Stem lesions to the hypocotyl also followed the same trend. Plants exposed to fluorodifen and grown in full light or total darkness were not significantly injured although necrosis of the cotyledons and hypocotyls was seen on plants that emerged in the light and on hypocotyls of dark grown plants after exposure to light. Light of 580 nm (yellow) and 620 nm (red) showed greater dry weight reduction than plants grown in white or blue light and stem lesion development increased with length of exposure. Light exposure was necessary for injury to occur although plants evidently compensated for injury in high light intensity by outgrowing the damage. No currently proposed theory adequately explains the observed light activation of ortho-substituted diphenylether herbicides. Acti- vation clearly required a xanthophyll pigment system which had been activated by an appropriate wavelength of light of adequate intensity. Persistence in Soil Walter g£_§1, (65) examined fluorodifen persistence under field conditions in Miller clay and Lufkin sandy loam soils and found less 16 than 10% remained 6 months after application. Persistence increased in the sandy loam soil when incorporated but not in the clay soil. Leaching of fluorodifen beyond the upper 7.5 cm of either soil was minimal but three months after application of 3.4 or 5.6 kg/ha to the Miller clay soil only 0.15 or 0.55 ppm, respectively, were found while 0.5 ppm was determined necessary for weed control. Weed counts in- dicated that herbicide persistence lasted 3 to 6 weeks. Adsorption of nitrofen and oxyfluorfen from aqueous solutions by muck soil and by kaolinite and bentonite soils saturated with hy— drogen or calcium ions was studied by Fadayomi and Warren (17). They found more than 80% of both herbicides was removed from solution by muck and bentonite soils but less than 40% was removed by the kaolinite soils. Desorption by four repeated extractions from muck and bentonite soils previously saturated with nitrofen and oxyfluorfen removed 5% or less of the adsorbed herbicides from muck and H-Al-bentonite soils but 40% of the nitrofen and 10% of the oxyfluorfen were desorbed from the Ca-bentonite soil. Leaching of muck soil, Ockley silt loam soil, and Bloomfield fine sand showed less than 2% of either herbicide ap- peared in the leachates which was consistent with the high soil adsorp- tivity and low water solubilities of nitrofen and oxyfluorfen. The effect of amendments of muck and clays to silica sand was bioassayed with sorghum seedlings and showed 1% muck increased GR50 concentrations by 24-fold for nitrofen and 14-fold for oxyfluorfen. A 1% amendment of Ca-kaolinite and H-Al-kaolinite resulted in a 2-fold increase in GRSO concentration for oxyfluorfen but nitrofen activity was not af— fected. This indicated some inactivation by clays occurred whereas increasing amendments of muck soil resulted in greater reduction of 17 herbicide activity. This also suggested that enough herbicide was still biologically available from Ca-bentonite soil since 10% to 40% was available for desorption. Absorption and Translocation Movement of 14C-fluorodifen from the roots of peanut seedlings was studied by Eastin (10) who found 90% to 95% of the radioactivity in the roots after 144 h of treatment while the remainder was confined to the stem with only traces found in the petiole and leaflets. Walter EEHEL- (65) examined absorption of 14C—fluorodifen from nutrient solu- tion containing 10 mg/ml by peanut, soybean, grain sorghum, and morning— glory [Ipomoea purpurea (L.) Jacq.] seedlings and found the herbicide was readily absorbed by the roots. Translocation was limited though to lower stems and leaves of all species with greater amounts found in the susceptible plants, morningglory and grain sorghum. An apparent correlation existed between translocation and sensitivity to fluoro- difen among the species tested. Application of 1l'C-fluorodifen in acetone to soybean leaflets resulted in little absorption by the treated leaflet after 48 h with almost no acropetal or basipetal translocation. In another investigation of 14C-fluorodifen translocation in peanut seedlings, Eastin (13) found 48 h after application to the roots, 97.5% of the radioactivity remained in the roots, 1.5% moved into the hypo— cotyl and less than 1% moved into the shoot. After 96 h, slightly greater amounts were found in the shoot (6.5%) and the hypocotyl (7.1%). These results support previous work which showed that translocation was limited in resistant plant species. Rogers (49) studied absorp- tion and translocation of 14C-fluorodifen from soybean roots and found 18 considerable uptake within 12 h. When soybean plants were grown in a 1 ppm solution for 1 day, 98.3% of the radioactivity was detected in the roots and 1.7% in the shoots but after 16 days, only 79.0% re- mained in the roots and 21.0% was found in the shoots. Root absorp— tion and translocation in cucumber (Cucumis sativus L. 'Ashley') was also studied by Eastin (11) who found that from solutions of 0.1, 0.5, and 1.0 ppm of 14C—fluorodifen, rapid movement into the leaves occurred ranging from 6.2% to 56.6%. This was further evidence that transloca- tion of l4C-fluorodifen was a major basis of selectivity between re- sistant peanut and susceptible cucumber. Absorption and translocation of nitrofen and oxyfluorfen in sorghum and pea have been studied by Fadayomi and Warren (18) who found no movement of 14C-herbicides from roots of sorghum (susceptible) or pea (resistant) although significant amounts of both were absorbed from the solution by the roots. In a second experiment, foliar absorption and translocation of these labeled herbicides from soybean and greenbean also indicated virtually no move- ment from the site of application while in a double pot experiment, shoot application was found to be more effective than root application in reducing growth. Leather and Foy (34) have examined uptake and movement of 14C- bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate] in corn, soy- bean and velvetleaf from preemergence treatments. Their results indi- cated that any radioactivity taken up remained in the roots but a sig- nificant amount of the 14C-bifenox absorbed by velvetleaf was trans- located to the shoot. Foliar application showed an increase in absorp- tion during 48 h following treatment but no visual damage was observed. Slight acropetal movement was found in all three plants with 2% of 19 the applied 14C-bifenox found in the culm and younger leaves of corn and 3% of the 14C found in the stem and leaves above the treated area in velvetleaf but no translocation was found in soybean plants. Root uptake and translocation of nitrofluorfen [2-chloro-l-(4- nitrophenoxy)-4-(trifluoromethyl)benzene] and oxyfluorfen in fababean (Vicia faba L.) and green foxtail [Setaria virdis (L.) Beauv.] was studied by Vanstone and Stobbe (63) who found uptake in roots was simi- lar in both plants with each herbicide and was proportional to the concentration applied. Acropetal movement occurred in fababean in both herbicides with 1.9% being found in the shoot after 1 day and 4.6% after 5 days with necrotic leaf spots visible within 5 days. These reports again confirmed the trend of root absorption but of lim- ited transport to the shoot. Foliar absorption and translocation of 14C-acifluorfen was exam- ined by Mangeot (37) on ivyleaf morningglory, a susceptible plant spe- cies and 'Williams' soybean which was tolerant. Examination of leaf washes after 24 h showed no significant difference in the amount of absorption of 14C-acifluorfen by either species (10.0%). Visual obser- vations and autoradiographs indicated translocation in the treated leaf and to the shoot above the treated leaf of morningglory occurred within 24 h of application. ll'C-acifluorfen was detected in all parts of morningglory within 6 h of treatment and at a concentration in the shoot greater than 3 ug/g of plant material which was the threshhold for injury. Characterization of the translocated 14C-material indi- cated 89.5% to 99.9% was 1l'C-acifluorfen. Soybean injury was observed only at the site of application and autoradiographs and extractions confirmed that little translocation had occurred. 20 Metabolism Fluorodifen degradation and metabolism has been extensively stud— ied by several researchers and considering its structural similarities to numerous currently used diphenylether herbicides, these studies could offer a predictive model for their pathway of degradation. Peanut seedlings have been the most thoroughly studied plant species and Eastin (10) in his early research with root applied fluorodifen- 1'-14C found after 48 h, 67.8% had been metabolized to p-aminophenol and 13.5% to p-nitrophenol while 17.4% remained as the parent compound. After 144 h, 94.3%, 0.9%, and 4.0%, respectively, of each compound were found. Less than 1% of the radioactivity was found in either 2-amino-fluorodifen (p-nitrophenyl-u,u,a—trifluoro-Z-amino-p-toly1 ether) or p-amino-fluorodifen (p-aminophenyl-a,o,o-trifluoro-2-nitro- p-tolyl ether) which could have been intermediates along a proposed minor pathway to p-nitrophenol and p-aminophenol. These results in- dicated hydrolysis of the ether linkage followed by reduction of the nitro group to an amino group, yielded p—aminophenol as the major degradation product. In further studies by Eastin (12) of the time-course degradation of fluorodifen—l'-14C in peanut seedling roots, 73.5% of the radioac- tivity found in the roots 2 h after treatment was detected as 140- fluorodifen, 13.6% as p—nitrophenol, 8.9% an unknown polar complex and 3.1% as bound residue. At the end of 72 h, only 2.0% was determined to be 14C-fluorodifen, 38.1% an unknown polar complex, 44.3% p- nitrophenol and 4.6% as bound residue with no p-amino-fluorodifen de— tected. This study indicated the presence of a mechanism in peanut 21 roots which rapidly metabolized a large portion of the root absorbed 1['Cmfluorodifen to p-nitrophenol and an unknown polar complex. Use of 14C-fluorodifen labeled in the trifluoromethyl carbon and 14C-fluorodifen labeled at the 1 position of the p-nitrophenol ring allowed Eastin (13) to further examine the metabolic degradation path- ways in roots. After 48 h of treatment with f1uorodifen-l'-14C, 31.6% of the radioactivity was determined to be the parent compound, 32.6% as p-nitrophenol and 30.0% as a highly polar water-soluble compound (Unknown 1) which was erroneously identified as p-aminophenol in his previous work (10). Compounds found in other plant components were identified as p-nitrophenol, Unknown [,and a small amount of 14C- fluorodifen. Extraction of fluorodifen-MOP3 from roots indicated a highly polar water-soluble compound (Unknown II) comprised 81.9% of the radioactivity after 48 h and 16.0% was identified as the parent compound. The radioactivity found in the plant parts above the root contained a small quantity of 14C-fluorodifen, Unknown 11, and 2-amino- 4-trifluoromethy1phenol. Fluorodifen-l'-14C did not produce detectable amounts of p-aminophenol, p-amino-fluorodifen, or p,2-diamino-fluoro- difen and fluorodifen-IACF3 did not yield any detectable amounts of 2-nitro—4-trifluoromethylphenol. These results lead to the conclusion that the degradative pathway followed was either reduction of the 2— nitro group followed by cleavage of the ether linkage or cleavage of the ether linkage leading to 2-nitro-4-trifluoromethylphenol. Reduc- tion followed by cleavage appeared the more likely pathway since the 2-amino—4-trif1uoromethylphenol found was a stable compound. The re- sulting breakdown products apparently were unequally conjugated with 22 plant constituents since Unknown 11 accounted for as much radioactiv— ity as p-nitrophenol and Unknown I combined. Shimabukuro 3; El. (52) examined metabolism of both fluorodifen- 1'-14C or fluorodifen-IACF3 tified metabolites by amino acid analysis and by mass, NMR and infra- from excised peanut leaf petioles and iden- red spectroscopy. Following 24 h of treatment, 14C-fluorodifen had been translocated into the leaf blades but showed no injury from ini- tial uptake although some localized necrotic areas appeared in younger leaves and the second or third leaf from the shoot apex. Metabolism resulted in a polar water-soluble conjugate which contained 75.9% of the applied 14C ring labeled fluorodifen, 3.2% as p-nitrophenol, 8.7% as fluorodifen, and 12.2% as an insoluble plant residue. Metabolism 14 of CF3-f1uorodifen resulted in isolation of 60.1% of the radioactiv- ity in four separate metabolites, 2.6% in the ether-soluble fraction, 11.8% as 14C-fluorodifen, and 25.5% as an insoluble plant residue. Identification of several of these compounds lead to the conclusion that the parent compound was first degraded by cleavage of the ether linkage. One of the products of the cleavage was identified as S-(2- nitro-4-trifluoromethylphenol)-glutathione which contained 28.4% of the radioactivity. The p—nitrophenol moiety formed an unidentified 0-conjugate which was incorporated at a slower rate into an insoluble residue (Figure 2). Glutathionefi§ftransferase in peanut catalyzed cleavage of fluorodifen but not metabolism of atrazine as observed in corn. This indicated definite substrate specificity of this enzyme between different plant species. Metabolism of fluorodifen in soybean roots has been examined by Rogers (49) who also found fluorodifen was primarily cleaved at the 23 ether linkage with reduction of the nitro substituents as minor prod- ucts. The rate of metabolism was determined to be rapid enough to serve as a protective mechanism for soybean. Locke and Baron (36) examined the fate of fluorodifen—1'-140 and 14CF3 in a suspension culture of tobacco cells and found after 15 days, 60% to 80% of the recovered radioactivity was incorporated in the cells. Metabolites present were characterized as conjugates of p-nitrophenol and included probable glucoside and amino acid or protein conjugates. Examination by Eastin (14) of the fate of 14C-fluorodifen in the susceptible plant species cucumber found after 24 h in a 1.0 ppm solu- tion, seedlings were visibly damaged with total collapse of tissue in 96 h. Autoradiographs after 24 h indicated radioactivity translocated to the leaves was located in the primary and secondary veins with 24.3% of the radioactivity found in the shoots. Radioactivity in the leaves was comprised of 45.1% 14C-fluorodifen, 23.6% p-nitrophenol, 30.5% as Unknown I, and 8.0% as insoluble plant residue. In a second study of cucumber root treatment with fluorodifen-1'-140 and fluorodifen— 14CF3, Eastin found metabolites in the roots, stems, cotyledons, and leaves. 0f the fluorodifen-l'-14C recovered from all plant sections, 17.0% to 53.6% was parent compound, 3.4% to 13.2% p-nitrophenol, and 15.4% to 38.2% Unknown 1. 0f the fluorodifen-IACF3 recovered, 15.0% to 48.1% was parent compound, 20.2% to 33.7% Unknown II and small amounts of various aminophenol products. Vanstone and Stobbe (63) found that in fababean leaf discs and leaf segments of green foxtail, little metabolism occurred after 4 h or 24 h with either nitrofluorfen or oxyfluorfen. Tissue injury was visible after 4 h with complete tissue destruction after 24 h at which 24 time a maximum of 8.0% of the oxyfluorfen and 5.4% of the nitrofluor- fen had been metabolized in both plant species. Metabolism of 14C-bifenox in soybean roots was examined by Leather and Foy (34) who found 98% of the radioactivity was present as nitro- fen with less than 1% as bifenox acids. Velvetleaf root extracts con- tained primary unaltered 14C—bifenox while shoot extracts contained 25% bifenox, 51% bifenox acids, 20% as an unidentified compound, and less than 1% nitrofen. Metabolism of 14C-acifluorfen in ivyleaf morningglory reported by Mangeot (37) indicated after 24 h, 10.5% of the translocated 14C- acifluorfen was metabolized in leaves above the treated leaf and 9.7% in leaves below the treated leaf. In soybean 24 h after treatment, 21.4% of the radioactivity found in the shoot above, 37.6% in the shoot below, and 75.4% in the treated leaf was identified as 14C-acifluorfen. Mode of Action Light activation and subsequent contact necrosis observed from diphenylethers prompted researchers to investigate their effects on photosynthesis in isolated chloroplasts and disruption of membrane integrity. Moreland ggigl. (44) examined the effects of nitrofen, MC-l478 (2,4,6-trichlorophenyl-4'-nitrophenyl ether) and fluorodifen on photophosphorylation and electron transport in spinach (Spinacia oleracea L.) and mung bean (Phaseolus aureus L. var. 'Jumbo') chloro- plasts and white potato tuber mitochondria. Compounds ranked in de- creasing order of inhibition: MC-l478 3_fluorodifen >> nitrofen in depressing noncyclic electron transport and coupled photophosphoryla- tion in chloroplasts. The location of action was concluded to be near 25 PSII and the site of oxygen evolution. MC-l478 and nitrofen inhibited mitochondrial electron transport in the presence of malate, NADH and succinate whereas fluorodifen did not inhibit electron transport. Interference of oxidative and photosynthetic phosphorylation were pos— tulated as modes of action for these diphenylether herbicides but no postulations could be made to elucidate the light activation phenomenon. Evaluation of the activity of 14 diphenylether herbicides by Bohn and Rieck (5) on isolated pea chloroplasts was conducted by monitor- ing 0 concentrations resulting from inhibition of coupled, uncoupled, 2 PSI, and PSII electron transport. Compounds examined included aci- fluorfen, nitrofen, oxyfluorfen, RH 8817, RH 32509, RH 34073, RH 41939, RH 2512, RH 35451, RH 1833, RH 4414, RH 4514, RH 5782, and RH 5347. None of the compounds tested inhibited PSI nor inhibited PSII greater than 35% at concentrations of 250 um. Compounds containing a carboxy- methyl (RH 5782) or carboxyethyl (RH 8817) group inhibited electron transport 54% and 64%, respectively. Compounds which inhibited elec- tron transport greater than 50% had slightly higher 1 values coupled 50 than uncoupled. Uncoupled 1 values included RH 8817 (12 um), oxy— 50 fluorfen (13 um), and nitrofen (20 um). Recent work done by Bugg g£_§1, (7) with HOE 29152 (methyl—2[4- (4-trifluoromethoxy)phenoxy]propanoate) and nitrofluorfen on pea seed- lings and spinach chloroplasts showed photosynthetic electron trans- port was inhibited but neither PSII or PSI activity were directly af- fected. Increase in the halftime for dark reduction of cytochrome f and resistance to either phenazine methosulfate or diaminodurene in- hibition by nitrofluorfen indicated the site of inhibition was in the plastoquinone—cytochrome f region between PSII and PSI. 26 Plant tissue damage from diphenylether herbicides usually appears as lesions or necrotic areas on treated plant tissue. Studies by Pereira ggflgl. (47) indicated nitrofen injured cabbage (Brassica oleracea L.) foliage and red head (Beta vulgaris L.) root sections by disruption of membranes but injury was reduced by application of exogenous sucrose which decreased cell permeability to nitrofen. Mem- brane disruption was shown to precede inhibition of photophosphoryla— tion and electron transport in a separate experiment on isolated spin- ach chloroplasts. Gorske and Hopen (24) examined nitrofen and oxyfluor— fen on the susceptible species purslane (Portulaca oleracea L.) and also found an increase in membrane permeability which led to stomatal closure. Phytotoxic symptoms of leaf pitting, epinasty, and water logging of cells were observed 4 h after treatment with complete leaf abscission after 24 h. Postulation of the sequence of events of the activity of both herbicides began with a change in membrane permeabil- ity of the guard cells followed by stomatal closure and further pene- tration to lower mesophyll cells with continued membrane disruption. Ethylene synthesis and leaf temperature elevation were determined to be secondary responses to herbicide treatment. No clear consensus among researchers exists as to whether mem- brane disruption precedes or follows inhibition of photosynthesis. The necessity of light for activity would suggest that disruption of photophosphorylation and consequential lack of ATP necessary for main- tainance of membrane integrity leads to visible cell disruption and leakage. 27 Selectivity Hawton and Stobbe (26) examined selectivity among rape (Brassica campestris L. var. 'Echo'), redroot pigweed (Amaranthus retroflexus L.), and green foxtail to postemergence application of nitrofen and found green foxtail and redroot pigweed, respectively, 5.8 and 63.3 times more sensitive than rape. Differential retention of water—soluble dyes showed green foxtail retained only 66% as much as rape while red- root pigweed showed no retention difference from rape. Uptake studies indicated redroot pigweed continued to absorb 14C-nitrofen 4 days after application although after 8 days green foxtail and rape had absorbed more 14C-nitrofen than redroot pigweed. Selectivity was therefore concluded not to be based on retention or absorption but on internal factors unique to each plant species. Intraspecific selectivity be- tween two cabbage varieties to postemergence applications of nitrofen was examined by Pereira ggflgl. (46) who concluded that increased cu- ticular wax increased the tolerance to nitrofen due to the less absorption. Differential translocation of fluorodifen from roots was deter— mined by Walter gg'gl. (65) as one basis of selectivity between the tolerant species of soybean and peanut and the susceptible species of morningglory and grain sorghum. Limited root translocation in soy— bean and rapid metabolism of fluorodifen was proposed by Rogers (49) as a protective mechanism but Fadayomi and Warren (18) concluded absorp- tion and translocation were not the mechanisms of selectivity of nitro— fen or oxyfluorfen in soybean and greenbean. Vanstone and Stobbe (63) found that nitrofluorfen and oxyfluorfen translocation and metabolism in fababean and green foxtail were also not responsible for selectivity 28 between these species. Velvetleaf was found by Leather and Foy (34) to be selectively less tolerant to bifenox than corn or soybean on the basis of greater absorption and translocation and slower metabolism. Cucumber, a susceptible species, was determined by Eastin (11) to rapidly absorb and translocate fluorodifen but degraded it slowly. Peanut seedlings were able to metabolize 82.6% of root absorbed fluor- odifen within 48 h and 96% within 144 h (13). Conjugation of fluoro- difen by glutathione Sftransferase was confirmed by Shimabukuro g£_§l, (52) in peanut roots while Frear and Swanson (12) also postulated that an enzyme system was responsible for metabolism in pea seedlings, a resistant species. Soybean, greenbean, scarlet runner bean (Phaseolus coccineus L.) and pea were tested for both preemergence and postemergence differen- tial sensitivity to nitrofen, fluorodifen, and oxyfluorfen by Fadayomi and Warren (19). They found that tolerance to preemergence treatments was greater in species which emerged rapidly while seed weight was not a significant factor in influencing tolerance. Differential selectivity between ivyleaf morningglory and soy- bean to acifluorfen as determined by Mangeot (37) indicated no dif— ference occurred in the amount of the radioactivity absorbed or trans— located between the species. In plant parts above the treated leaf, morningglory had 20 times more acifluorfen per unit dry weight than soybean and in the shoot below, morningglory had 6 times more than soybean. 0f the 14C-acifluorfen translocated in morningglory only 10% was metabolized whereas from 24.6% to 78.6% was metabolized in soybean, thus both translocation and metabolism were involved in selectivity. 10. ll. 12. l3. 14. 29 LITERATURE CITED Agaev, M. G. 1974. Population density as a regulatory factor of plant development. Dokl. Akad. Nauk. Sssr. Ser. Biol. 217: 705-708. (In Russian). Avery, A. G., S. Satina, and J. Rietsema. 1959. Blakeslee: The genus Datura. Ronald Press, New York. 289 pp. Bateson, W. and E. R. Saunders. 1902. Experimental studies in the physiology of heredity. Datura Reports to the Evolution Com- mittee of the Royal Soc. Beverley, R. 1705. The history and present state of Virginia. Republished for Inst. of Early Am. Hist. and Cul. at Williamsburg, Va. Univ. N. C. Press, 1947. Bohn, J. A. and C. E. Rieck. 1979. The activity of diphenyl ethers on chloroplast. Proc. South. Weed Sci. Soc. 32:323 (Abstr.). Buchanan, G. A., C. S. Hoveland, and M. C. Harris. 1975. Re- sponse of weeds to soil pH. Weed Sci. 23:473-477. Bugg, M. W., J. Whitmarsh, C. E. Rieck, and W. S. Cohen. 1980. Inhibition of photosynthetic electron transport by diphenyl ether herbicides. Plant Physiol. 65:47-50. Chesnut, V. K. 1898. Principal poisonous plants of the United States. USDA Bulletin No. 20. 60 pp. Crockett, L. J. 1977. Wildly successful plants. Macmillan Pub. Inc., New York. 268 pp. Eastin, E. F. 1969. Movement and fate of p-nitrophenyl—o,o,o- trifluoro-Z-nitro-p tolyl ether-l'-14C in peanut seedlings. Plant Physiol. 44:1397-1401. Eastin, E. F. 1971a. Movement and fate of fluorodifen-l'-14C in cucumber seedlings. Weed Res. 11:63-68. Eastin, E. F. 1971b. Degradation of fluorodifen-l'-14C by peanut seedling roots. Weed Res. 11:120-123. Eastin, E. F. 1971c. Fate of fluorodifen in resistant peanut seed- lings. Weed Sci. 19:261—265. Eastin, E. F. 1972. Fate of fluorodifen in susceptible cucumber seedlings. Weed Sci. 20:255-260. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 3O Erdman, W. and M. W. Emmel. 1950. Some poisonous plants in Florida. Univ. of Fla. Bul. 468. 47 pp. Fadayomi, 0. and G. F. Warren. 1976. The light requirement for herbicidal activity of diphenyl ethers. Weed Sci. 24:598-600. Fadayomi, 0. and G. F. Warren. 1977a. Adsorption, desorption and leaching of nitrofen and oxyfluorfen. Weed Sci. 25:97-100. Fadayomi, 0. and G. F. Warren. 1977b. Uptake and translocation of nitrofen and oxyfluorfen. Weed Sci. 25:111-114. Fadayomi, 0. and G. F. Warren. 1977c. Differential activity of three diphenyl ether herbicides. Weed Sci. 25:465-468. Frazee, R. W. and E. W. Stoller. 1974. Differential growth of corn, soybean, and seven dicotyledonous weed seedlings. Weed Sci. 22:336-339. ' Frear, D. S. and H. R. Swanson. 1973. Metabolism of substituted diphenylether herbicides in plants. Enzymatic cleavage of fluoro- difen in peas. Biochem. Physiol. 3:473-482. French, C. M. and P. W. Santelmann. 1976. Phytotoxicity and soil activity of RH 2915. Proc. South. Weed Sci. Soc. 29:407 (Abstr.). Gleason, H. A. and A. Cronquist. 1968. Manual of vascular plants of northeastern United States and adjacent Canada. Van Nostrand Reinhold Co., New York. 810 pp. Gorske, S. F. and H. J. Hopen. 1978. Effects of two diphenylether herbicides on common purslane (Portulaca oleracea). Weed Sci. 26:585-588. Hardin, J. W. and J. M. Arena. 1974. Human poisoning from native and cultivated plants. Duke Univ. Press, Durham, N.C. 167 pp. Hawton, D. and E. H. Stobbe. 1971. Selectivity of nitrofen among rape, redroot pigweed and green foxtail. Weed Sci. 19:42-44. Holm, L., J. V. Pancho, J. P. Herberger, and D. L. Plucknett. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp. Holm, L., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The world's worst weeds. Distribution and biology. Univ. Press of Hawaii, Honolulu. 609 pp. Holm, R. E. and M. R. Miller. 1972 a. Weed seed germination re- sponses to chemical and physical treatments. Weed Sci. 20:150-153. Holm, R. E. and M. R. Miller. 1972b. Hormonal control of weed seed germination. Weed Sci. 20:209-212. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 31 Hoveland, C. S., G. A. Buchanan, and M. C. Harris. 1976. Re- sponse of weeds to soil phosphorus and potassium. Weed Sci. 24: 194-201. Johnson, W. 0., G. E. Kollman, C. Swithenbank, and R. Y. Yih. 1978. RH 6201 (Blazer): A new broad spectrum herbicide for post- emergence use in soybeans. J. Agric. Food Chem. 26:285. Jordan, T. N. 1979. 1979 Extension county agent weed survey of problem weeds in Indiana. Purdue Univ., West Lafayette, Ind. 20 pp. Leather, G. R. and C. L. Foy. 1978. Differential absorption and distribution as a basis for the selectivity of bifenox. Weed Sci. 26:76-81. Lewis, W. H. and M. P. F. Elvin-Lewis. 1977. Medical botany. Plants affecting man's health. John Wiley & Sons, New York. 515 pp. Locke, R. K. and R. L. Baron. 1972. Preforan metabolism by tobacco cells in suspension culture. J. Agric. Food Chem. 20:861-867. Mangeot, B. L. 1978. Activity and selectivity of acifluorfen. Ph.D. dissertation. Univ. of Kentucky. Lexington, Ky. 101 pp. Mathis, W. D. and L. R. Oliver. 1975. Effects of bentazon on dif- ferent weed species at various stages of growth. Proc. South. Weed Sci. Soc. 28:35 (Abstr.). Matsunaka, S. 1969a. Activation and inactivation of herbicides by higher plants. Residue Rev. 25:45-58. Matsunaka, S. 1969b. Acceptor of light energy in photoactivation of diphenylether herbicides. J. Agric. Food Chem. 17:171-175. McGlamery, M. D. 1975. 27th annual Illinois custom spray opera- tors training school. Univ. of 111. Urbana-Champaign. Meggitt, W. F. 1980. Weed control guide for field crops. Mich. State Univ. Ext. Bul. E-434. Coop. Ext. Serv., Mich. State Univ., East Lansing, Mi. 27 pp. Mikolich, J. R., G. W. Paulson, and C. J. Cross. 1975. Acute anti- cholinergic syndrome due to Jimson seed ingestion: Clinical and laboratory observation in six cases. Ann. Intern. Med. 83:321-325. Moreland, D. E., W. J. Blackmon, H. G. Todd, and F. S. Farmer. 1970. Effects of diphenylether herbicides on reactions of mito- chondria and chloroplasts. Weed Sci. 18:636-642. Parochetti, J. V. 1975. Control of jimsonweed and three broad- leaved weeds in soybeans with herbicides. Proc. Northeast. Weed 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 32 Pereira, J. F., W. E. Splittstoesser, and H. J. Hopen. 1971a. Mechanism of intraspecific selectivity of cabbage to nitrofen. weed 8C1. 19:647-651. Pereira, J. F., W. E. Splittstoesser, and H. J. Hopen. 1971b. Response of plant tissues to nitrofen. Weed Sci. 19:662-666. Pollak, T. and G. Crabtree. 1976. Effect of light intensity and quality on toxicity of fluorodifen to green bean and soybean seed- lings. Weed Sci. 24:571-573. Rogers, R. L. 1971. Absorption, translocation and metabolism of p-nitrophenyl-o,u,u-trif1uoro-2-nitro-p-tolyl ether by soybeans. J. Agric. Food Chem. 19:32-35. Safford, W. E. 1920. Daturas of the old world and new. An. Rep. Smith. Inst. Publ. 2644. Schultes, R. E. and A. Hofmann. 1980. The Botany and Chemistry of Hallucinogens. Charles C. Thomas Pub., Springfield, 111. 437 pp. Shimabukuro, R. H., G. L. Lamoureux, H. R. Swanson, W. C. Walsh, L. E. Stafford, and D. S. Frear. 1973. Metabolism of substituted diphenylether herbicides in plants. II. Identification of a new fluorodifen metabolite, S-(2-nitro-4-trifluoromethylphenyl)- glutathione in peanut. Pest. Biochem. and Physiol. 3:483-494. Smith, T. S. and E. M. Rahn. 1972. Growth and development of jimsonweed as affected by certain environmental factors. Abstr. Weed Sci. Soc. Am. p. 23. Sommerville, D. N. and L. M. Wax. 1971. Influence of incorpora- tion depth on chloramben activity. Weed Sci. 19:394-397. Southern Weed Science Society. 1980. Weed Science: The tie that binds, bends. Res. Rep. 33:1-243. Stearn, W. T. 1957. An introduction to the Species Planatarium and conjugate botanical work of Carl Linnaeus. Bartholomew Press. Stoller, E. W. and L. M. Wax. 1973. Periodicity of germination and emergence of some annual weeds. Weed Sci. 21:574-580. Stoller, E. W. and L. M. Wax. 1974. Dormancy changes and fate of some annual weed seeds in the soil. Weed Sci. 22:151-155. Stroube, E. W. 1980. Personal communication. Toole, E. H. and E. Brown. 1946. Final results of the Duvel buried seed experiment. J. Agric. Res. 72:209-210. United States Department of Agriculture. 1970. Selected weeds of the United States. Agriculture Handbook No. 366. 463 pp. 62. 63. 64. 65. 66. 67. 33 United States Department of Agriculture. 1972. Extent and cost of weed control with herbicides and an evaluation of important Vanstone, D. E. and E. H. Stobbe. 1978. Root uptake, transloca- tion and metabolism of nitrofluorfen and oxyfluorfen by fababeans (Vicia faba) and green foxtail (Setaria viridis). Weed Sci. 26: 389-392. Vanstone, D. E. and E. H. Stobbe. 1979. Light requirement of the diphenylether herbicide oxyfluorfen. Weed Sci. 27:88-91. Walter, J. P., E. F. Eastin, and M. G. Merkle. 1970. The persis- tence and movement of fluorodifen in soils and plants. Weed Res. 10:165-171. Wax, L. M. 1977. Incorporation depth and rainfall on weed con- trol in soybeans with metribuzin. Agron. J. 69:107-110. Yih, R. Y. and C. Swithenbank. 1975. New potent diphenyl ether herbicides. J. Agric. Food Chem. 23:592-593. 34 .voms m mm: us moaovw>m on use muoaw mnu a“ ucomoum I muoam .xamu :Boaxc: mo use vows m on ou umcfiaumumw I ucommum .sofiucmuum unnumaoo wcwuwsvmu moouu mama a“ wmouammwfis huo> I aoesou .aouo m CH mumo3 mzofiuom “mos m aou use macaw coxcmu I Hmofioafium .aouo m :H momma mnowumm umoe m we N aou DSu waoam voxcmu I msoauwmu .uuoe A.QV mazumu .um> Enwcosmuum manumm nufiz m:oEoco:%m a .Anmv momma wauoz mo moau< ofiemmmwooo < Eoum coaumfiuowcfi vmumwa mo coHumeQEoo m muammmumou H manmfim vmuH mume mchH awxuse mfi>mamowsw mummuu cows: uoH>0m mHosnocm> amen mammvosm muamwa vanawmne oflansamm snowsHSoo coax Ouumsm mfiamuame amusm mwxm>oamonomwo ouuouoz muwum< .m Hmwcmm muwm mumou coamnoq vcmaom ummz .mfimma%aom oHnEDHoo amuH Show cmuwfixmm mvmcmo mwmwcomaH mnvfinamnoz wfimamow 3oz mwumMHam humwcsm m%cmM hm3hoz Hauwum me3mm mamhao Hmmmz snowmawcmm >cmsumo .A Enacosmuum chauon mo Emapoua woo3 m mm wcfixsmu can coausnauumwv vases m.H manna 35 Figure 1. Structures of diphenylether herbicides. 36 ACIFLUORFEN 9 Cl C-O' Na + mooom 5-[2- oblate-Mtrifluoromethyl) phenom-2 nitrobenzoic acid BIFENOX (II) 'C— 0— -CH3 Q?°wQ? methyl 5-(2,4-dlchlorophenoxy)-2-nitrobenzoate FLUORODIFEN N02 . Q? 0Q? ~o P -nitrophenyl ct , 0‘ , " -Irmuoro-2-nitro-/J -Iolyl ether NITROFEN CI ..@.@.. 2, 4-dichlorophenyl P -nitropheny| ether NITROFLUORFEN Cl .3.@.@~. 2-chloro-1-(4-nItrophenoxy)-4-( trifluoromethyl) benzene OXYFLUORFEN CI O-CH2-CH3 ...@.@-2 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-( trifluoromethyl) benzene O acQ?°Q?~°2 2-chloro-1 -( 3-carboxyethyl-a-nilrophenoxy)-4-( trifluoromethyl) benzene RH 8817 CH0 ”CH2 CH3 37 Figure 2. Proposed metabolic pathway of fluorodifen degradation in peanut roots by Shimabukuro £5 31. (52). 38 mac—mm”. w4m340m2_ + nozmzaomtza mo Emissazooo a mac—mum w..m=..0m2. ’ . _ . a... . . . o QZDOm—zoo ZBOZXZ: . ”no «oz «1 «:2 -O- (I) «02¢: « . :oo9«:9z.9:9z.9«z9 1919000: H :w :m mw<¢wmmz<¢hum wZO.I._.<._.:._0 Zwu_00m0:..m «oz @013: of «oz CHAPTER 2 INTERFERENCE BY DATURA STRAMONIUM L. VAR. STRAMONIUM AND DATURA STRAMONIUM L. VAR. TATULA (L.) TORR. IN SOYBEAN [GLYCINE MAX (L.) MERR.] ABSTRACT Interference and replacement series studies were conducted with each of two varieties of jimsonweed to determine any differential effects on soybean growth parameters and the corresponding responses of each jimsonweed variety to soybean competition. Each jimsonweed variety was planted at population densities of O, 4.4, 8.8, and 17.6 pl/m2 into a soybean population density of 17.6 p1/m2. A second in— terference study was conducted in a natural stand of var. tatula with densities of 0.7, 1.4, 2.7, 5.3, and 10.7 p1/m2 in soybean. Soybean seed weight was reduced 46% by var. stramonium and 58% by var. tatula while soybean dry matter was reduced 42% by both varieties at a den-l sity of 4.4 pl/mz. The number of soybean flowers, pods, and nodes per plant were reduced by both jimsonweed varieties by 45%, 41%, and 41%, respectively, at a population density of 8.8 p1/m2. Variety tatula accumulated 2.5 times more dry matter than var. stramonium at a population density of 17.6 pl/m2 when competing with a soybean plant population of 17.6 p1/m2. Variety stramonium was observed to have a highly branched, shorter growth pattern with greater fruit production per unit dry matter than var. tatula which had a taller growth habit that over-topped the soybean canopy. In a natural stand of var. tatula, at a density of 0.7 and 5.3 p1/m2, soybean yield was reduced 22% and 39 40 46% respectively. Replacement series studies with 5 population den- sity ratios indicated a competitive interference response existed be- tween soybean and both jimsonweed varieties but interference did not appear to be mediated by an allelochemic mechanism. 41 INTRODUCTION Datura stramonium L. has been listed among the eight most impor- tant broadleaf weeds in soybean in the world (9) and has been ranked as a serious, principal or common weed in 33 countries and present as a weed but of undetermined rank in 31 other countries (8). In the U.S., it has been reported to be the 5th most difficult annual broadleaf weed to control in corn and soybean in Illinois (11) and the 5th most common weed of agronomic crops in Indiana (10). In Michigan, it is among the three special weed problems in terms of difficulty to control in soybean (13). 0f the numerous surveys and studies in which jimsonweed has been included, very few have identified the plant species used at the vari- ety level. Two different plants currently called Datura stramonium L. were identified as separate species by Linnaeus as early as 1737 (14) and were later regarded by Torrey (15) as two varieties of the same species. Gleason and Cronquist (7) have listed them as Datura stramonium L. var. stramonium having white flowers and green stems and Datura stramonium L. var. tatula (L.) Torr. having purplish flowers and purple stems. These plants are reportedly very similar, differing only in the gene for pigment color (2) and have been found to have the same protein composition (6). No previous work has examined the morphological response of each variety when grown in competition with agronomic crops nor if the crop is differentially affected by either variety. Research with several Ipomoea species have shown different competitive effects on crops was primarily due to morphological char— acteristics of each species (5, 15). Light interception by tall 42 morningglory [Ipomoea purpurea (L.) Roth] was reported to be an impor- tant means of competition as with other weed species such as jimsonweed which overtop the crop canopy (1, 3, 4, 12). Research has therefore been conducted to determine if any dif- ferential interference effects on soybean growth parameters occurs between either jimsonweed variety and to observe differential morpho- logical responses of both jimsonweed varieties to soybean competition. MATERIALS AND METHODS Jimsonweed seeds used in both studies were collected from mature capsules of var. tatula in the fall of 1978 from Kalamazoo county in southwestern lower Michigan and var. stramonium from Clinton county in central lower Michigan. 'Harosoy 63' soybean seeds were planted on Capac sandy clay soil composed of 45.3% sand, 18.0% silt, 36.7% clay, and 3.7% organic mat- ter in East Lansing on May 18, 1979 in 76 cm rows. Each row of a four row plot was overseeded with a single row hand planter with one of the two varieties of jimsonweed. Control of other weeds was achieved by preplant incorporation of 0.84 kg/ha of trifluralin (o,a,a-trifluoro- -2,6-dinitro-N,N-dipropyl-p-toluidine) and by hand weeding throughout the growing season. Within the first three weeks after emergence of both soybean and jimsonweed, population densities for both studies were established. For the interference study, soybean plants were thinned to 17.6 p1/m2 while both varieties of jimsonweed were thinned to population densities of 0, 4.4, 8.8, and 17.6 p1/m2. A second in- terference study was conducted in Monroe county in southeastern Michigan on a Selfridge sandy loam soil composed of 73.5% sand, 8.0% silt, 18.5% 43 clay, and 4.2% organic matter which was naturally infested with var. tatula. Soybean seeds were planted on June 15, 1979 in 76 cm rows and emerging jimsonweed seedlings were thinned to population densities of O, 0.7, 1.4, 2.7, 5.3, and 10.7 pl/m2 within the first 3 weeks af- ter emergence. Population densities for the replacement series study were based on a total plant population of 17.6 pl/mz. Mixtures of soybean and one of the two jimsonweed varieties were composed of weed to crop ratios of 100:0% (17.6:0 pl/mz), 75:25% (13.2:4.4 pl/mz), 50:50% (8.8:8.8 pl/mz), 25:75% (4.4 13.2 p1/m2), and 0:1002 (0:17.6 pl/mz). Plot dimensions for all three experiments were 6.7 m in length and four 76 cm rows in width. A buffer zone 0.6 m wide was maintained at each end of the plot and as a band across the center of each plot. The center two rows between the buffer zones of each plot were used for data collection, 2.44 m of which were removed during soybean pod fill while the other 2.44 m of the center two rows were harvested at maturity. Measurements taken on five representative plants of soybean at pod fill included dry weight, plant height, flower number, pod number and node number. Five jimsonweed plants were also selected to measure dry weight, plant height, flower number, capsule number, and branch number. The remaining soybean and jimsonweed plants in these plots were also removed and dry weights obtained. The interference study in East Lansing was designed as a 2 by 4 factorial with four replications and the replacement series study was designed as two separate experiments with five treatments each with three replications. The second interference study was designed with six treatments and three replications. All experiments were conducted 44 with a randomized complete block design. Data were subjected to analysis of variance and mean separation by Fishers protected LSD at the 5% level. RESULTS AND DISCUSSION Interference of soybean dry matter accumulation was significantly reduced by the presence of both varieties of Datura stramonium L. at the lowest population density tested (Figure 1) but soybean dry weight reduction due to interference was not statistically different between the varieties. At a density of 4.4 pl/m2 both varieties appeared to have expressed their maximum competitive effect reducing soybean dry weight approximately 42%. Higher jimsonweed population densities did not significantly further reduce soybean dry matter accumulation. Reduction of soybean seed weight (Figure 2) was found to be greater from infestations of var. tatula than var. stramonium at the 4.4 pl/m2 population density but at higher population densities yield reductions were not significantly lower or different between the two varieties. Soybean seed weight was reduced by 46% by var. stramonium and 58% by var. tatula at the low plant density. Both jimsonweed varieties reduced soybean flower number by 45%, pod number by 41% and nodes per plant by 41% when averaged over jim- sonweed population densities of 8.8 and 17.6 pl/mz. Soybean plant height was not affected by var. stramonium but var. tatula caused a 10% elongation of soybean plants at a weed density of 17.6 pllmz. A greater competitive effect was found from var. tatula than var. stra- monium on soybean and the maximum interspecific competitive effect occurred at very low densities. 45 Dry weight of var. tatula (Figure 3) was found to increase lin- early and did not appear to reach a maximum dry weight level at the densities tested. Accumulation of dry weight for var. stramonium . reached a maximum at 8.8 pl/m2 followed by a leveling off of dry weight at 17.6 pllmz. This indicates var. tatula was able to continue to compete inter- and intraspecifically with increasing population den- sities while var. stramonium appeared less competitive. Seed weight production (Figure 4) was not found to differ between the two varie- ties and appeared to reach a maximum at 8.8 pl/ha. This indicates that a greater portion of var. stramonium dry weight was composed of fruit than var. tatula which shows foliage dry weight was greater for var. tatula. Part of the differential dry matter accumulation between the varieties may be explained by different photoperiod responses and subsequent shift from vegetative to fruit production earlier in var. stramonium than var. tatula. After appearance of the first true leaves, var. stramonium began to produce flowers and subsequent fruit capsules throughout the growing season. At each flowering point two branches were produced, each of which produced flowers which produced capsules and branches and so on. This led to a plant which was not significantly taller (95.5 cm) than soybean (97.5 cm) but had numerous branches which crowded the soybean foliage at the top of the canopy. Flowering did not occur in var. tatula until 3 to 4 weeks later than var. Eggg- monium. This allowed apical dominance to be maintained longer and thus produced taller plants (127.1 cm) with fewer branches, which pen- etrated through the soybean canopy allowing for greater light inter- ception. This possibly allowed higher densities to produce a greater amount of dry matter since var. tatula foliage was almost completely 46 above the soybean canopy and continued to produce dry matter after soybean vegetative growth had ceased. Reduction in soybean yield would therefore occur with low densities of both varieties but with greater interference from var. tatula. In a separate population density study in a natural infestation of var. tatula, soybean seed weight was reduced 22% with only 0.7 pl/m2 and by 46% at a population density of 5.3 pl/mz. Higher population densities did not reduce soybean seed weight further. Soybean dry weight was reduced by 11% and 32% for the 0.7 and 5.3 pl/m2 popula- tion densities, respectively. This suggests var. tatula provided less competition to soybean in the vegetative stage and had a greater com- petitive influence during the pod development stage. Dry weight and seed weight accumulation in var. tatula was found to increase up to 5.3 p1/m2 but at twice this population density dry weight did not increase further. In a replacement series study with var. stramonium and var. tatula, soybean dry matter accumulation was not significantly altered from predicted amounts at any population density combination with either variety (Figures 5A and B). Both varieties of jimsonweed also followed the same predictive model. These trends indicate interference between jimsonweed and soybean was due to competition for light, nutrients, and/or water rather than an allelochemic intermediate under field conditions. 10. ll. 12. 13. 47 LITERATURE CITED Barrentine, W. L. 1974. Common cocklebur competition in soybeans. Weed Sci. 22:600-603. Bateson, W. and E. R. Saunders. 1902. Experimental studies in the physiology of heredity. Datura reports to the Evolution Com- mittee of the Royal Soc. Black, C. C., T. M. Chen, and R. H. Brown. 1969. Biochemical basis for plant competition. Weed Sci. 17:338—344. Buchanan, G. A. and E. R. Burns. 1971. Weed competition in cot- ton. I. Sicklepod and tall morningglory. Weed Sci. 5:576-582. Crowley, R. H. and G. A. Buchanan. 1978. Competition of four morningglory (Ipomoea spp.) species with cotton (Gossypium hirsutum). Weed Sci. 26:484-488. Debourcieu, L. 1977. Application of thin layer electro-focusing to the chemotaxonomy of the genus Datura (Solanaceae). Plant Med. Phytother. 11:12-15. Gleason, H. A. and A. Cronquist. 1968. Manual of vascular plants of northeastern United States and adjacent Canada. Van Nostrand Reinhold Co., New York. 810 pp. Holm, L., J. V. Pancho, J. P. Herberger, and D. L. Plucknett. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp. Holm, L., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The world's worst weeds. Distribution and biology. Univ. Press of Hawaii, Honolulu. 609 pp. Jordan, T. N. 1979. 1979 Extension county agent weed survey of problem weeds in Indiana. Purdue Univ. West Lafayette, Ind. 20 pp. McGlamery, M. D. 1975. 27th annual Illinois custom spray opera- tors training school. Univ. of 111., Urbana-Champaign. McWhorter, C. G. and J. M. Anderson. 1979. Hemp sesbania (Sesbania exaltata) competition in soybeans (Glycine max). Weed Sci. 27:58-64. Meggitt, W. F. 1980. Weed control guide for field crops. Mich. State Univ. Ext. Bul. E-434. Coop. Ext. Serv., Mich. State Univ., East Lansing, Mi. 27 pp. 14. 15. 16. Stearn, W. T. 48 1957. An introduction to the Species Planatarium and conjugate botanical work of Carl Linnaeus. Bartholomew Press. Torrey, J. 1824. Catalogue of plants of New York. 160 pp. Wilson, H. P. in soybeans. and R. H. Cole. 1966. Morning glory competition Weeds 14:49-51. 49 Figure 1. Soybean dry matter production (g/m2) as affected by population densities of 4.4, 8.8, and 17.6 pl/m2 of either Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. 50 «5323.. 9:. , ad ed 8.3.. <._D._.<._. .m<> 'IIIIII'IIIIII sazosfitm .m<>||||||.IIIIII I/ cow cow com com zw/swvus 51 Figure 2. Soybean seed production (g/mz) as affected by pop- ulation densities of 4.4, 8.8, and 17.6 pl/m2 of either Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. 52 «5325.. mfiw ed Ev c WJIIJ H853 2: 32:: .m<> III II IIIII) 55.2052“me .m<> can can zw/swvuo 53 Figure 3. Dry matter production of Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. at population densities of 4.4, 8.8, and 17.6 pl/m2 when grown with soybean at a population density of 17.6 pl/mz. 54 «5323.. at «a 3. InIIIIIJIIJi on: 5.3—20.25"...“ .m<>1 \ \ .\\ AEN \ can \\ mo.om._ (43.—.4... .m<> \ . cow zw/SWVHS LP ('1’ Figure 4. Seed production of Datura stramonium L. var. stramonium or Datura stramonium L. var. tatula (L.) Torr. at pop- ulation densities of 4.4, 8.8, and 17.6 pl/m2 when grown with soybean at a population density of 17.6 pl/mz. 56 «5923.. ofiw ad Ev W. I1 I14 8.3.. ED_ZOE \ «33.—.42. .m< ." 'I \ ’ III\ 2:. com zw/SWVH'O Figure 5A. 57 Replacement series responses to population density mixtures of soybean and Datura stramonium L. var. 2 stramonium measured as dry matter accumulation (g/m ) of both plant species as compared with a hypothetical model. Population density crop to weed ratios included: 100:0 z - 17.6: 0.0 pl/mg 75:25 % - 13.2: 4.4 p1/m2 50:50 z - 8.8: 8.8 p1/m2 25:75 % - 4.4:13.2 pl/m2 0:100% - 0.0:17.6 p1/m Values differing from the expected dry matter accumula- tion (dashed lines) for soybean, var. stramonium, and the sum of both plant species by less than 93.0 g, 170.0 g, and 210.0 g, respectively, are not signifi- cantly different at the 5% level as determined by LSD. 58 o\o o\o o3. Z0w o m« am we cow me on m« o _ m _ \ ll \ x x / \ II OOF I \ xx xx I \ ll CON \ x x I. \ II can x xx xx .l 2: \x x x x x I. as x x x x x x -..5o cos 2:_ZO_2 zw/swvus Figure 5B. 59 Replacement series responses to population density mixtures of soybean and Datura stramonium L. var. tatula (L.) Torr. measured as dry matter accumulation (g/mz) of both plant species as compared with a hypo- thetical model. ratios included: 100:0 75:25 50:50 25:75 A 0:100% I-I- 7. 3. 8. 4. 0. Population density crop to weed 6: 0.0 pl/mg 2: 4.4 pl/m2 8: 8.8 p1/m2 4:13.2 p1/m2 0:17.6 pl/m Values differing from the expected dry matter accumula- tion (dashed lines) for soybean, var. tatula, and the sum of both plant species by less than 96.0 g, 156.0 g, and 195.0 g, respectively, are not significantly dif- ferent at the 5% level as determined by LSD. 60 0\0 mm cop car Z0w c <43h 1,2: l 8« com . occ . can can och zw/SWVH'O CHAPTER THREE EFFICACY OF OXYFLUORFEN AND RH 8817 ON TWO VARIETIES OF JIMSONWEED [DATURA STRAMONIUM L. VAR. STRAMONIUM AND VAR. TATULA (L.) TORR.] IN SOYBEAN [GLYCINE MAX (L.) MERR.] ABSTRACT Studies were designed to examine the relative phytotoxicity of oxyfluorfen [2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethy1) benzene] and RH 8817 [2-chloro-l-(3-carboxyethyl-4-nitrophenoxy)-4- (trifluoromethy1)benzene] to two varieties of jimsonweed when applied alone or in combination with alachlor [2-cthro-2',6'-diethy1-N-(methoxy- methy1)acetanilide] or metribuzin [4-amino-6-gggg-butyl-3(methylthio)- gg-triazin-5(4H)-one] in soybean fields. The activity or phytotoxicity of the diphenylether herbicides on both jimsonweed varieties was depen- dent upon the soil organic matter content, method of herbicide applica- tion, length of time after application, and presence of additional herbicides. Shallow incorporation of oxyfluorfen into the soil did not provide consistent season-long control even at oxyfluorfen rates of 1.12 kg/ha unless 2.24 kg/ha of alachlor or 0.56 kg/ha of metribuzin were also applied. RH 8817 was found to be effective throughout the growing season with shallow incorporation at rates of 1.12 to 1.40 kg/ha or in combination with 2.24 kg/ha alachlor or 0.56 kg/ha metribuzin. A comparison of preemergence and shallow incorporation treatments of the two diphenylether herbicides to assess jimsonweed control and 61 62 soybean injury was conducted on a Capac sandy clay soil with 3.7% or- ganic matter content and under average daily temperatures of 15.8 C with 6.8 cm of precipitation during the 14 days following planting. Subjected to these conditions, soybean stand counts were reduced by oxyfluorfen at 0.84 kg/ha or greater and from RH 8817 at 1.40 kg/ha or greater with both application methods, but only oxyfluorfen at 1.12 kg/ha significantly reduced soybean yield. Visual ratings indicated that oxyfluorfen and RH 8817 caused 36.0% and 19.4% more injury to soy- bean, respectively, when applied preemergence than when shallow incor- porated. The same herbicide treatments were applied to Selfridge sandy loam soil with 4.2% organic matter content and under average daily temperatures of 21.3 C with 0.89 cm of precipitation during the 14 days following planting. Preemergence oxyfluorfen and RH 8817 application at rates greater than 0.56 kg/ha at this location produced visible soybean injury but no significant injury was found when the herbicides were shallow incorporated. The soybean stand was not decreased by either diphenylether or with either method of application. Jimsonweed control was somewhat reduced by shallow incorporation of both diphenylether herbicides. 63 INTRODUCTION Soybean production in Michigan has undergone a rapid increase in recent years. In 1976, only 266,000 ha of soybean were harvested in Michigan (8) while in 1979, 457,000 ha of soybean were harvested (9), an increase of 172% in only 3 years. Associated weeds also ac- companied introduction of crops into a new area and jimsonweed, which typically infests soybean fields, has increased as a problem in Michigan. Adjacent states which also produce soybean, such as Indiana, Illinois, and Ohio have ranked jimsonweed the fifth most common and difficult annual broadleaf weed to control (4, 7, 12). Effective post- emergence herbicides such as bentazon [3-isopropyl-1H-2,l,3-benzothia- diazin-4(3H)-one2,2-dioxide] and acifluorfen (sodium 5-[2-chloro-4- (trifluoromethyl)phenoxy]-2-nitrobenzoate) currently provide acceptable control (6, 10, 2, 3) but no currently registered herbicides provide efficaceous preemergence control throughout the growing season with- out injury to soybean (10, ll, 13). Oxyfluorfen, a recently introduced diphenylether herbicide, has shown excellent preemergence control of jimsonweed at rates of 0.25 to 0.56 kg/ha with little injury to soybean at rates of 1.12 kg/ha (1, 14). Another developmental diphenylether herbicide, RH 8817, which has been reported to effectively control tall morningglory, [Ipomoea pugpurea (L.) Roth], ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.], and common cocklebur (Xanthium pensylyanicum Wallr.) preemergence with 1.12 kg/ha (2), also shows promise in control— ling jimsonweed. 64 This study was designed to compare the relative activity of oxy- fluorfen and RH 8817 on two varieties of jimsonweed in soybean under Michigan field conditions. This investigation examined the enhance- ment of control with combinations of either diphenylether herbicide with alachlor or metribuzin and investigated the injury to soybean from the diphenylether herbicides applied preemergence or shallowly incorporated. MATERIALS AND METHODS Preliminary field studies were conducted in southeastern Michigan in Monroe county (Location I) and southwestern Michigan in Berrien county (Location 11) in natural stands of jimsonweed [Datura stramonium L. var. tatula (L.) Torr.] in 1979 to evaluate the efficacy of several herbicide combinations applied preemergence, preplant incorporated to a depth of 5 cm or postemergence in soybean. In 1980 additional field experiments were conducted at Locations I and II and at three separate sites in central lower Michigan, at St. Johns (Location III) and Dewitt (Location IV) h1C11nton county, and at East Lansing (Location V) in Ingham county. Location III was severely infested with naturally oc- curring Datura stramonium L. var. stramonium while Location IV contained a significantly lower density of this variety. Location V was the site of a previous year's study with introduced seeds of both varieties scattered at low densities throughout the field. Soil types, mechani- cal analysis and organic matter content were determined for each loca- tion (Table l). Plots consisted of four 76 cm rows, 9.14 m in length arranged in a completely randomized block design at Locations 11, III, and IV. 65 Experiments at Locations I and V were laid out in a completely random- ized block design with split blocks to examine preemergence vs. rotary hoe incorporation treatments of oxyfluorfen and RH 8817. Herbicides were applied within 3 days of planting with a tractor mounted sprayer which traveled 6.7 km/hr and delivered 212 L/ha at a pressure of 2.1 kg/cmz. Immediately following herbicide application, all treatments were shallow incorporated twice over to an approximate depth of 1.25 cm with a rotary hoe. The center two rows of each plot were rated visually 4 and 12 weeks after emergence for herbicide efficacy and injury to soybean. One-half of each plot was maintained weed-free by hand-hoeing through- out the growing season to eliminate any competition to soybean growth in order to evaluate yield reduction from herbicide injury. At harvest, 4 m of the center two rows which had been maintained weed-free, were removed and processed through a mechanical thrasher. Stand counts were taken of the number of soybean plants remaining at harvest to determine the mortality rate from diphenylether herbicides. Soybean yields were not taken at Location I due to late season water damage nor at Location 11 where soybeans were replanted into the treated plots due to poor emergence from an earlier planting. Soybean planting dates were grouped by early season planting on May 23, 27, and 28 at Locations 111, V, and IV and late season planting on June 25 at Location I with replanting at Location II on June 30. Locations planted in late June emerged under warmer conditions (Tables 2 and 3). Soybean varieties included 'Beeson,' 'Corsoy,' 'Corsoy,' 'Evans,‘ and 'Harosoy 63' at Locations I to V, respectively. 66 Data for each location were subjected to analysis of variance and mean separation by Duncan's multiple range test at the 5% level. RESULTS AND DISCUSSION Preliminary field studies in 1979 indicated that oxyfluorfen, acifluorfen, and RH 8817 were active on var. tatula and were more ef- ficaceous but also more injurious when applied preemergence than pre- plant incorporated to a depth of 5.0 cm at both Locations 1 and 11. Other preemergence herbicide treatments which included metribuzin and combinations of naptalam (N-l-naphthylphthalamic acid) and dinoseb (2-§g£-butyl-4,6-dinitrophenol) were not effective in controlling var. tatula at rates which did not cause severe soybean injury. Field studies in 1980 were conducted on five soil types with or- ganic matter contents ranging from 3.5% to 5.5% and under three differ- ent environmental conditions. Locations III, IV, and V were planted in late May and had an average daily temperature of 15.8 C for 14 days following planting with a total of 6.8 cm of precipitation (Table 2). These conditions slowed soybean growth causing hypocotyls to remain in the crook stage and in contact with treated soil for a prolonged period of time. .Locations I and II were planted in late June and were subjected to warmer environmental conditions than the earlier planted locations. Temperatures at Location I averaged 21.3 C with 0.89 cm of precipitation for the 14 days following planting. Environmental con- ditions at Location II were not reported since data on soybean injury, stand counts and yields were not collected. At Location IV on Owosso sandy clay loam soil with 3.5% organic matter content (Table 4), both oxyfluorfen and RH 8817 provided 67 acceptable control of var. stramonium at all rates tested 4 weeks after soybean emergence. Late season control with oxyfluorfen alone was unacceptable at all rates tested but the addition of 2.24 kg/ha of alachlor or 0.56 kg/ha of metribuzin significantly improved control. RH 8817 applied alone at 0.84 kg/ha or at 1.12 kg/ha in combination with alachlor provided 90% or greater control 4 weeks after emergence. Early season soybean injury resulted from all treatments and was seen as leaf crinkling and necrosis, hypocotyl lesions and reduction in population densities. Only oxyfluorfen combinations with alachlor or metribuzin and higher rates of RH 8817 reduced stand counts to levels lower than for untreated control plots at the end of the growing sea- son. Soybean yield reduction was found only with oxyfluorfen applied alone at 1.12 kg/ha or in combination with alachlor. At Location III, on a Parkhill clay loam soil with 5.5% organic matter content (Table 5), early season control of var. stramonium was acceptable with all herbicide treatments except oxyfluorfen at 0.56 kg/ha. After 12 weeks, all oxyfluorfen treatments were unacceptable except when applied in combination with alachlor. RH 8817 effectively controlled jimsonweed at 1.40 kg/ha alone or in combination with ala- chlor or at rates of 0.84 or 1.12 kg/ha in combination with metribuzin at 0.56 kg/ha. Visual injury to soybean was seen with both herbicides but only at rates of 0.84 or 1.12 kg/ha or greater with oxyfluorfen and RH 8817, respectively. Soybean stand counts though were not sig- nificantly lower except from oxyfluorfen used in combination with metri- buzin. No soybean yield reductions were observed from any herbicide treatment. A comparison of the results from Locations III and IV in- dicated that an increase of 2.0% in soil organic matter content reduced 68 control of var. stramonium and reduced soybean injury without decreas— ing soybean stand counts or corresponding yields. A comparison of the effects of preemergence vs. shallow incorpor- ation of oxyfluorfen and RH 8817 on both varieties of jimsonweed and on soybean was conducted at Location V on Capac sandy clay soil with 3.7% organic matter content (Table 6). Excellent control was found 4 weeks after emergence with all treatments except for oxyfluorfen at 0.28 kg/ha. However after 12 weeks shallow incorporation of oxyfluor- fen at 0.56 kg/ha resulted in unacceptable jimsonweed control. The shallow incorporation did not affect the control of jimsonweed with RH 8817. Visual evaluation of soybean plants indicated that shallow incorporation significantly reduced injury from oxyfluorfen and RH 8817 compared to preemergence applications. However oxyfluorfen at rates of 0.84 and 1.12 kg/ha reduced soybean stand counts with both applica- tion methods. RH 8817 at rates of 1.40 and 1.68 kg/ha caused soybean stand count reduction with either method of application. The same rates of both herbicides applied preemergence also caused soybean yield re- duction but the shallow incorporation treatments of both herbicides did not reduce yields. Control of var. tatula was examined at Location I on Selfridge sandy loam soil with 4.2% organic matter content (Table 7). Preemer- gence and shallow incorporation treatments of both herbicides applied alone resulted in unacceptable jimsonweed control except for shallow incorporation applications of RH 8817 at rates of 1.12 to 1.68 kg/ha. The addition of either 2.24 kg/ha of alachlor or 0.56 kg/ha of metri- buzin to shallow incorporation treatments of oxyfluorfen or RH 8817 significantly enhanced jimsonweed control at both early and late season 69 ratings. Soybean injury ratings indicated that all preemergence treatments except oxyfluorfen at 0.28 kg/ha produced injury whereas shallow incorporation of these same treatments caused no significant injury. The addition of alachlor or metribuzin to shallow incorpora- tion treatments of oxyfluorfen and selected RH 8817 treatments also resulted in visible soybean injury. Stand counts taken at the end of the growing season though, showed no reduction in soybean population densities from any treatments. Results from Location II are reported in Appendix A. 10. ll. 12. l3. 14. 70 LITERATURE CITED French, C. M. and P. W. Santelmann. 1976. Phytotoxicity and soil activity of RH 2915. Proc. South. Weed Sci. Soc. 29:407 (Abstr.). Hayes, R. M. and J. R. Overton. Comparison of selected diphenyl- ether herbicides for weed control in soybeans. Proc. South. Weed Sci. Soc. 32:69 (Abstr.). Johnson, W. 0., G. E. Kollman, C. Swithenbank, and R. Y. Yih. 1978. RH 6201 (Blazer): A new broad spectrum herbicide for post- emergence use in soybeans. J. Agric. Food Chem. 26:285. Jordon, T. N. 1979. 1979 Extension county agent weed survey of problem weeds in Indiana. Purdue Univ., West Lafayette, Ind. 20 pp. Mangeot, B. L. 1978. Activity and selectivity of acifluorfen. Ph.D. dissertation. Univ. of Kentucky, Lexington, Ky. 101 pp. Mathis, W. D. and L. R. Oliver. 1975. Effects of bentazon on different weed species at various stages of growth. Proc. South. Weed Sci. Soc. 28:35 (Abstr.). McGlamery, M. D. 1975. 27th annual Illinois custom spray opera- tors training school. Univ. of 111., Urbana-Champaign. Michigan agricultural statistics. 1977. Mich. Agr. Reporting Ser. Lansing, Mi. 64 pp. Michigan agricultural statistics. 1980. Mich. Agr. Reporting Ser. Lansing, Mi. 80 pp. Parochetti, J. V. 1975. Control of jimsonweed and three broad- leaved weeds in soybeans with herbicides. Proc. Northeast. Weed Sci. Soc. 29:19-25. Sommerville, D. N. and L. M. Wax. 1971. Influence of incorpora- tion depth on chloramben activity. Weed Sci. 19:394-397. Stroube, E. W. 1980. Personal communication. Wax, L. M. 1977. Incorporation depth and rainfall on weed con- trol in soybeans with metribuzin. Agron. J. 69:107-110. Yih, R. Y. and C. Swithenbank. 1975. New potent diphenyl ether herbicides. J. Agric. Food Chem. 23:592-593. 71 Table 1. Physical and chemical analysis of soils from 5 field locations used in herbicide trials. Mechanical analysis Organic matter Sand Silt Clay Location Soil type % I Selfridge sandy loam 4.2 73.5 8.0 18.5 II Whitaker sandy clay loam 4.1 52.4 18.0 29.6 III Parkhill clay loam 5.5 35.7 32.7 31.6 IV Owosso sandy clay loam 3.5 45.7 26.7 27.6 V Capac sandy clay 3.7 45.3 18.0 36.7 72 Table 2. Temperature and precipitation dataa for Location 111, V, and IV, 7 days preceding and 14 days following soybean planting on May 23, 27, and 28, respectively. Temperature Maximum Minimum Average Precipitation Date (C) (C) (C) (cm) Me): 15 17.2 3.9 10.6 0.03 16 19.4 1.7 10.6 17 15.6 10.0 12.8 2.16 18 17.8 10.0 13.9 0.13 19 22.2 10.0 16.1 20 23.3 7.8 15.6 21 26.1 '7.8 17.2 22 29.4 8.3 18.9 23 28.3 10.0 19.4 24 26.7 15.6 21.1 25 23.3 7.8 15.6 26 21.7 4.4 13.3 27 26.7 5.6 16.1 28 30.0 12.8 21.7 29 28.9 16.1 22.8 30 27.8 16.1 22.2 0.71 31 23.3 11.7 17.8 June 1 15.0 6.7 11.1 0.81 2 23.9 12.8 18.3 1.24 3 21.7 12.8 17.2 0.46 4 22.2 8.3 15.6 5 22.8 8.9 16.1 0.94 6 27.2 16.1 21.7 0.40 7 25.0 15.0 20.0 1.96 8 16.7 6.7 11.7 9 18.3 6.1 12.2 0.28 10 15.0 2.2 8.9 11 21.1 2.2 11.7 aStatistics were collected from the National Oceanic and Atmospheric Administration, Environmental Data and Information Service, Local Climatological Data for Capitol City Airport, Lansing, Michigan, May and June, 1980. 73 Table 3. Temperature and precipitation dataa for Location I, 7 days preceding and 14 days following soybean planting on June 25, 1980. Temperature Maximum Minimum Average Precipitation Date (C) (C) (C) (cm) June 18 24.4 8.3 16.7 19 25.6 10.0 17.8 1.14 20 23.3 7.8 15.6 21 25.0 10.6 17.8 22 27.8 12.8 20.6 23 27.8 13.9 21.1 24 26.1 17.8 22.2 25 28.3 16.1 22.2 26 32.2 17.2 25.0 27 25.0 16.1 20.6 28 31.1 15.6 23.3 29 31.1 15.0 23.3 30 20.6 13.3 17.2 July 1 27.8 11.1 19.4 0.05 2 27.2 16.1 21.7 3 28.3 13.3 21.1 4 27.2 15.0 21.1 0.08 5 30.6 16.7 23.9 0.76 6 24.4 13.3 18.9 7 26.7 11.7 19.4 8 30.6 17.8 24.4 9 23.9 13.9 18.9 aStatistics were collected from the National Oceanic and Atmospheric Administration Environmental Data and Information Service, Local Climatological Data for Detroit Metropolitan Airport, Detroit, Michigan, June and July, 1980. 74 .ummu mwamu uaaauasa m.amo::o cu wawvuouom Hm>mH Nm man an usmummwfio %HuamUHwflcwwm uoc mum Hmuuua 08mm ecu 2n om30HH0m .msome Ham comaumn wounafiou on cue nuass mnmumamumo Houucou noon sow uoouxo .mnaaaou canoes names a .aowumUHHaem wafizoaaom zaoumfivmeaw Eu mN.H mo Somme mumawxouaam cm cu mwvHUfinumn mo aofiumuoosouaw Boaamnm sow com: mos won humuou mo Houucoo n.ucmucou nouuma usamw Iuo Nm.m sufis Haom Emoa xmao zvamm ommoso no >H coaumuoq um owma .wN >mz do vmuu=uuo wawuamam .GmmnTAOm flaw EdHfiOEmhum .Hm> 2H EDHCOEmHum NHSUMQ GO GHNSDHHqu HO HOHfiUmHm fins”? fiOHumflHn— IEoo cw no macaw woaaaam naww mm Ho cmwuoaamzxo mo musoaummuu GOHumuoauooca 3oaamnm mo uumwmm .6 maan m 75 .ummu mwamn mfimfiuass m.amucsm ou wcfiwuouom Ho>oa Nm msu um ucmummmfiv mauamofimwcwwm uo: mum Houuma mamm mnu >n woSOHHow .mcmmE HHm somsumn woumafioo on one Jessa muwumsmuma Houucou :uon sow unmoxw .ma53Hoo assufi3 memo: n .GOHumUfiHamm masonHOM >Houmwvmeaa Eu mN.H mo :uamv mumswxouaem cm on meowUHnHm: mo coaumuoauoucfi 3oHHmsm pom mom: mos mo: zumuou oH Nm ecu um ucmummmHv zHucmoHMHame Hos mum HmuumH mEmm ecu kn voon IHom .mcwme HHm cmw3uon woumoEou on one 50Hs3 mumuoEmqu Houuaou :uon How unease .maasHoo :quHa mammZn .:0HumuHHamm wGHonH0m mHmumvaEEH ao mN.H mo Luaow oumEonuaam cm ou mowHoHnHoc mo COHumuoauooaH aoHHmsm How wow: mos mo: zumuou 4m mus OHO« O OOH m O m O m O O.O Hooosoo smommoomO mun HHOO Hun Os sue mm m HO m OOH OO.H mso H«O« mus HO sue mm m OOH m HO Os.H mso OOOO OOm OO auO Om m HO m OOH «H.H ms OOOO O OO Hum HO m OO m OOH HO.O mso OHOO Ouo OH Hus HO ms OO ms OO O0.0 HHOO mm mus HOOH on Om muH HO m OO m OOH «H.H mus «OOH mus Os sum Os ms OO m HO s0.0 mso OOON Ouo OH mum OO so OH ms OO sm.O mso OOO« Ous sO mum OH on OO ms «O O«.O mmHOOOHHHxO COHumHomHoucH 30HHmnm on OOO« mus ss so: OO m OOH m OOH OO.H son HOOO s OH mus OH m OOH m OOH Os.H mus OHO« Ous «O muH HO m OOH m OOH «H.H mso HO«H Ouo HH ous HO m OOH m OOH s0.0 mso OOOO O OO HuO Os ms OO m HO O0.0 HHOO HO m OOO m OH mo OO m OOH m OOH «H.H H OHH« O OH mom OO m OOH m OOH sO.O mso HOOO Ous HO suH Hm ms OO m OOH O0.0 m OOOO OH HO mum OH O HO ms Om O«.O smHAOOHHHxO musmmumammum HmHHOHO HHO HHO HOV HHO HmOHOHO mommaommoe UHmH> unsou mamum husncH mxmw3 NH mxmm3 H mumm wmcommou ammn%0m .H EchoEmHum manum mo Houucoo n.uamuoou Houums UHcmwuo Nn.m £HH3 HHom hmHu mvamm omnmo co > GOHHmuoH an oon .NN hmz so wouusuoo wsHuamHm .H EbHcoEmuum assume we mOHumHHm> 03u Ho muauxHa m so Hwa mm Ho cmwuosHmwxo mo muamsummuu muaowumaomun Ho GOHumHoauoocH aoHHmsm mo Hummwm .0 OHan m 77 Table 7. Effect of shallow incorporationa or preemergence treatments of oxyfluorfen or RH 8817 applied alone or in combination with alachlor or metribuzin on Datura stramonium L. var. tatula (L.) Torr. and soybean. Planting occurred on June 25, 1980 at Location I on Selfridge sandy loam soil with 4.2% organic matter content. Control of Soybean var. Latulab Response Rate 4 weeks 12 weeks Injury Treatments (kg/ha) (%) (%) (%) Preemergence Oxyfluorfen 0.28 40 c-h 17 a-d 3 ab 0.56 57 f-l 27 a-e 20 c-f 0.84 60 g-m 50 e-k 37 gh 1.12 68 h-p 45 d-j 30 fgh RH 8817 0.56 50 e-k 13 abc 17 b-f 0.84 67 h-o 33 b-g 27 e-h 1.12 67 h-o 70 i-q 30 fgh 1.40 68 h-p 90 n-q 30 fgh 1.68 78 l-q 83 l-q 40 h Shallow incorporation Oxyfluorfen 0.28 7 ab 23 a-e 3 ab 0.56 43 d-i 45 d-j 3 ab 0.84 33 b-g 30 b-f 3 ab 1.12 68 h-p 67 h-o 10 a-d RH 8817 0.56 30 b-f 20 a-d 0 a 0.84 40 c-h 10 abc 3 ab 1.12 65 h-n 37 c-h 7 abc 1.40 65 h-n 33 b-g 7 abc 1.68 60 g—m 50 e-k 10 a-d Oxyfluorfen + alachlor 1.12 + 2.24 93 n-q 90 n-q 20 c-f 1.12 + 3.36 93 n-q 97 pq 27 e-h RH 8817 + alachlor 1.12 + 2.24 90 n-q 75 k-q 10 a-d 1.40 + 2.24 92 n-q 98 q 10 a-d 1.12 + 3.36 85 l-q 82 l-q 23 d-g 1.40 + 3.36 93 n-q 83 l-q 13 a-e Oxyfluorfen + metribuzin 0.84 + 0.56 97 pq 95 opq 20 c-f RH 8817 + metribuzin 0.84 + 0.56 87 m-q 73 j-q 17 b-f 1.12 + 0.56 93 n-q 95 opq 7 abc Untreated control 0.0 0 a 0 a 0 a aA rotary hoe was used for shallow incorporation to an approximate depth of 1.25 cm immediately following application. bMeans within columns, except for both control parameters which can be compared between all means, followed by the same letter are not significantly different at the 5% level according to Duncan's multiple range test. CHAPTER 4 RELATIVE RESPONSES OF TWO VARIETIES OF JIMSONWEED (DATURA STRAMONIUM L.) AND SOYBEAN [GLYCINE MAX (L.) MERR] TO PREEMERGENCE APPLICATIONS OF OXYFLUORFEN AND RH 8817 ABSTRACT Greenhouse studies were designed to determine relative sensitiv- ities of Datura stramonium L. var. stramonium and Datura stramonium L. var. tatula (L.) Torr. to preemergence applications on greenhouse mix soil of oxyfluorfen [2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4- (trifluoromethyl)benzene], RH 8817 [2-chloro-1-(3-carboxyethyl-4- nitrophenoxy)-4-(trifluoromethyl)benzene], metolachlor [2-chloro-N- (2-ethyl-6-methylphenyl)-N-(2-methoxy1-1—methylethyl)acetamide], alachlor [2-chloro-2',6'-diethy1-N-(methoxymethyl)acetanilide], and metribuzin [4-amino-6-pggp-butyl-3(methylthio)-§§-triazin-5(4§)one] and showed no significant differences in GR values between the two 50 varieties for any single herbicide treatment. Relative GR50 visual injury values showed metribuzin was 1.9 times more active than both diphenylether herbicides and 11.8 times more active than both acetan- ilide herbicides on both varieties. Oxyfluorfen activity on var. tatula was found to be increasingly reduced as soil organic matter levels increased from 1.5% to 8.2% organic matter while activity of RH 8817 was not reduced at soil organic matter levels beyond 5.5%. RH 8817 activity was 20% to 40% lower than oxyfluorfen only on the 5.5% organic matter soil. 78 79 Injury of both soybean and var. tatula from vapors from treated soil was greater from oxyfluorfen than RH 8817. Injury from both com- pounds was greater on wet than dry soils and decreased with increased soil organic matter levels. Growth chamber studies were conducted at three different day-night temperature regimes to determine the ef- fect of preemergence treatments of oxyfluorfen and RH 8817 on hypocotyl injury to soybean grown in three different organic matter soils. In- jury increased as day-night temperatures and organic matter levels de— creased. RH 8817 was found to be only slightly less injurious to soy- bean hypocotyls than oxyfluorfen. 80 INTRODUCTION Diphenylether herbicides were first developed in the U.S. in 1962. Nitrofen (2,4-dichlorophenyl p-nitrophenyl ether), the first commercial compound, was targeted for preemergence control of barnyard grass (Echinochloa crusgalli Beauv.) in transplanted rice (Oryza sativa L.) (8). Other selective preemergence diphenylether herbicides were later introduced for corn (Zea mays L.), cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), rice, soybean and other large-seeded legumes, sunflower (Helianthus annus L.), wheat (Triticum aesticum L.), and numerous vegetable crops (1, 7, 11, 15). Leguminous crops have been found to be injured on the hypocotyl hook by nitrofen, oxyfluorfen, and fluorodifen (p-nitrophenyl u,o,a- trifluoro-Z-nitro—p-toly1 ether) when soil applied which indicated that the primary site-of-action was the shoot zone (3, 4) especially since no leaching of diphenylether herbicides from various soils has been found (2, l4). Injury is also seen in the shoot portion above the hypocotyl and may result from diphenylether herbicide vapors from treated soil. Vapor loss from sand and sandy loam soils of several dinitroani- line herbicides has been reported to range between 18% to 35% in 24 h and to have increased as soil moisture and temperature increased (12, 13). Both foxtail millet [Setaria italica (L.) Beauf.] and wild oat (Avena fatua L.) growth have been shown to be inhibited by herbicide vapors from treated soils (6, 10). Research has therefore been conducted to determine the relative responses of two varieties of jimsonweed and soybean to oxyfluorfen 81 and RH 8817 uptake from the soil solution and from soil vapors and the factors affecting herbicide availability. MATERIALS AND METHODS Cultural Practices - Greenhouse Experiments conducted in the greenhouse received approximately 750 DE In-2 sec”1 of light supplemented with fluorescent lighting during a 16 h photoperiod. Temperatures ranged from 30 C-day to 20 C-night and relative humidity ranged from 30% to 60%. All plants were watered by surface irrigation twice daily. Differential Response of Jimsonweed Varieties Datura stramonium L. var. stramonium seeds were collected from a natural stand in Clinton county and Datura stramonium L. var. tatula (L.) Torr. from Monroe county in the fall of 1979. Seeds were sorted to obtain uniformity of size and color. All experiments with Datura stramonium L. contained 20 seeds per 480 ml double waxed paper cup and planted at a depth of 1.25 cm in a greenhouse soil mixture of sand: peat:loam (1:1:1, v/v/vl) with 15% organic matter. Surface applica- tions were made with a moving belt sprayer delivering 212 L/ha at a pressure of 2.1 kg/cmz. Commercial formulations of oxyfluorfen and RH 8817 were compared at ten rates ranging from 0.11 kg/ha to 1.12 kg/ha, four rates of alachlor and metolachlor from 1.12 kg/ha to 4.48 kg/ha, and eight rates of metribuzin from 0.11 kg/ha to 0.90 kg/ha. Visual ratings of injury of hypocotyls, cotyledons, and primary leaves were made 14 days after emergence (l4-DAE) and were expressed as a percent of an untreated control. The experiment was conducted in 82 the greenhouse and was arranged as a 5 by 2 factorial in a completely randomized block design with eight replications. Role of Soil Organic Matter Content Greenhouse studies were conducted to determine the effect of in- creased amounts of soil organic matter on the control of Datura stra— monium L. var. tatula (L.) Torr. on two diphenylether herbicides. Five rates of commercial formulations of oxyfluorfen and RH 8817 rang- ing from 0.22 kg/ha to 1.12 kg/ha were used. All treatments were ap- plied preemergence to three soils (Table 1) with organic matter con— tents of 1.5%, 5.5%, and 8.2% and visual injury ratings were taken l4-DAE and expressed as a percent of an untreated control. The exper- iment was conducted as a 2 by 5 by 3 factorial in a completely random- ized block design with eight replications. Activity of Herbicide Vapors from Soil This experiment was conducted in the greenhouse to determine the amount of injury to soybean or var. tatula from vaporization of oxy- fluorfen and RH 8817 from treated soils. Plastic pots 14 cm in diameter and 16 cm deep (Figure 1) were filled with a greenhouse soil mixture with either 20 seeds of var. tatula or 1 soybean seed planted in the center of the pot. A separate shallow plastic pot with a glass tube, 3 cm in diameter and 4 cm tall which penetrated through the bottom of the pot, contained treated soil from which vaporization was to occur. This shallow pot which measured 12 cm in diameter and 4 cm deep, was placed over soybean plants in the third trifoliolate or over the planted jimsonweed seeds. Soybean plants were exposed to vapors from treated 83 soilsvfilflu11411after application while soils were treated 7 days before emergence in the var. tatula experiment. A low organic matter content soil (LOMC), 1.5%, and a high organic matter content soil (HOMC), 8.2%, were used in the treatment pots. These soils remained at air dryness or were brought to field capacity once daily. Four rates each of oxyfluorfen and RH 8817 were used rang- ing from 0.56 kg/ha to 2.24 kg/ha in the soybean study and 0.07 kg/ha to 0.56 kg/ha in the soil organic matter content study. Visual injury ratings were taken 7 days after treatment (7-DAT) for soybean and 14-DAE for var. tatula. These experiments were arranged as 2 by 4 by 2 by 2 factorial with completely randomized block design with eight replications each. Soybean Hypocotyl Injury from Diphenylether Herbicides Growth chamber experiments were conducted to determine the rela- tive amounts of injury to emerging soybean hypocotyls from preemergence treatments of oxyfluorfen and RH 8817 and the influence of temperature and soil organic matter content on injury. Plants received 350 DE m-2 sec.1 during a 16 h photoperiod with a relative humidity of 70%. Two soybean seeds were planted in 480 m1 double wax paper cups at a depth of 2.5 cm. Three temperature schemes were used; high regime--29 C-day and 18 C-night; middle regime--24 C-day and 13 C-night; low regime-- 18 C-day and 7 C-night. Three soils (Table 1) were used with organic matter contents of 1.5%, 5.5%, and 8.2%. All pots were surface irri- gated daily to bring the soils to field capacity. Herbicide treatments consisted of preemergence applications of oxyfluorfen and RH 8817 at four rates ranging from 0.28 kg/ha to 1.12 84 kg/ha. Visual hypocotyl injury ratings were taken after the first trifoliolates appeared on the controls. The experiment was conducted as a 2 by 4 by 3 by 3 factorial in a completely randomized block de— sign with eight replications. Data for each experiment were subjected to analysis of variance and mean separation by Fishers protected LSD at the 5% level. RESULTS AND DISCUSS ION Differential Response of Jimsonweed Varieties Examination of GR50 values (Table 2) indicates preemergence ap- plications of oxyfluorfen and RH 8817 to greenhouse mix soil were able to control var. stramonium and var. tatula at approximately equal rates for both varieties. In a comparison of two acetanilide herbicides, slightly higher herbicide rates were required to inhibit growth of var. stramonium than var. tatula. More metolachlor was required than alachlor by 0.4 to 0.6 kg/ha to reduce growth. The same rate of metri- buzin controlled both varieties. Examination of GR50 values averaged over both varieties of Datura stramonium L. indicate both diphenylether herbicides required 1.9 times more than metribuzin and both acetanilides required 11.8 times more than metribuzin. Visual injury to both varieties from oxyfluorfen and RH 8817 ap- peared as lesions which girdled the hypocotyl at the point of contact with the treated soil, these generally occurred 1 to 4 days after emer- gence depending upon herbicide application rates. At higher rates, girdling continued until the hypocotyl was reduced to a thin strand of tissue which was unable to support the shoot material above the hy- pocotyl. Achlorotic lesions also occurred on the cotyledons and on 85 primary leaves which also showed crinkling, epinasty, and shortened leaf tips. Acetanilide herbicide injury symptoms were seen as severely crinkled leaves and shortened hypocotyls while metribuzin injury showed characteristic triazine injury symptoms of necrosis at the leaf margins. Role of Soil Organic Matter Content Preemergence applied oxyfluorfen activity on var. tatula (Figure 2) was significantly decreased as soil organic matter (OM) increased at all levels tested. Oxyfluorfen, at a rate of 1.12 kg/ha on soils with 1.5%, 5.5%, and 8.2% organic matter, control of var. tatula was 94%, 82%, and 60%, respectively. This decreased response to increased soil organic matter content indicates reduction in activity had not leveled off at the rates tested. This loss of activity with increased organic matter content is particularly important for Michigan soils where variations of soil type within the same field show large differ- ences in organic matter content and possibly wide fluctuations in weed control with oxyfluorfen. RH 8817 preemergence activity on var. tatula (Figure 3) also de- creased with increased soil organic matter content but activity was not significantly reduced at soil organic matter levels greater than 5.5%. RH 8817, at a rate of 1.12 kg/ha on soil with 1.5%, 5.5%, and 8.2% organic matter, control was 96%, 65%, and 66%, respectively. Since RH 8817 activity on the 5.5% and the 8.2% OM soils was not dif- ferent, an equilibrium concentration between biologically available RH 8817 in the soil solution and bound RH 8817 on the soil organic colloid evidently was reached on the 5.5% 0M soil and was not reduced further by increased soil organic matter content. 86 Comparison of oxyfluorfen and RH 8817 activity on the 1.5% and 8.2% OM soils showed no differences in var. tatula control at either soil organic matter level. Oxyfluorfen was significantly more active than RH 8817 on the 5.5% organic matter soil (Figure 4). At rates of 0.45 and 0.67 kg/ha, oxyfluorfen was twice as active as RH 8817, but at higher rates of 0.90 and 1.12 kg/ha, oxyfluorfen was only 20% to 40% more active than RH 8817. This reduction in RH 8817 activity was due to reduced availability through greater binding to soil or- ganic matter compared to oxyfluorfen. Activity of Herbicide Vapors from Soil Injury to var. tatula from vapors from soil applied oxyfluorfen and RH 8817 (Figure 5) was found to be related to both soil moisture and soil organic matter content. Slight injury was observed from dry 1.5% organic matter content soil (LOMC) but the injury level was not different between the two herbicides while from dry 8.2% organic mat- ter content soil (HOMC), only slight injury was observed. This in- dicates that on dry soils both herbicides were able to volatilize from the soil surface but were increasingly bound as organic matter con- tent increased. Sensitivity of var. tatula to vapors of oxyfluorfen and RH 8817 from wet LOMC soil (Figure 5) was detected at the lowest rate tested of 0.07 kg/ha with 25% and 8.8% injury, respectively. At the highest rate tested, 0.56 kg/ha, oxyfluorfen and RH 8817 produced an injury rating of 79% and 48%, respectively. These results indicate that in- jury from vapors from oxyfluorfen were from 1.6 to 2.8 times greater than from RH 8817 on wet LOMC soil. 87 Wet HOMC 8011 showed a similar response difference between oxy- fluorfen and RH 8817. Activity was significantly greater for each herbicide from LOMC soil than HOMC soil by approximately 2.1 times for oxyfluorfen and 2.3 times for RH 8817. Injury to soybean plants from vapors of oxyfluorfen from dry soils ranged from 9% to 19% at rates of 1.12 to 2.24 kg/ha, respec- tively and did not differ between high or low organic matter content. The maximum injury to soybean plants from RH 8817 vapors from both dry soils was 6.5% at a rate of 2.24 kg/ha. Visual injury from both dry soils was not great enough from either herbicide to account for the damage to soybean often time seen in the field following preemer- gence applications of these herbicides. On wet soils, injury to soybean was significantly greater than on dry soils for both herbicides at all the rates tested (Figure 6). The injury level from vapors of RH 8817 on LOMC and HOMC did not dif- fer significantly at rates of 0.56 to 2.24 kg/ha. This indicates that either the availability of RH 8817 to vaporize was not affected by soil organic matter content or soybean plants were able to rapidly metabolize the RH 8817 absorbed by the leaves. Increased soil organic matter content reduced the amount of oxyfluorfen injury from applica- tion rates of 0.56 and 2.24 kg/ha by 2.3 to 1.3 times on LOMC and HOMC soils, respectively. Injury to soybean on LOMC soil from oxy- fluorfen was greater than RH 8817 on either soil at all rates but on HOMC soils was only greater at rates of 1.68 or 2.24 kg/ha. The results of both vapor studies indicated that herbicide injury was application rate dependent for both herbicides and that both plant species studied were injured more from oxyfluorfen treatments but soil 88 organic matter content influenced only the injury from oxyfluorfen. Greater soybean injury from oxyfluorfen could have been due to a selec- tive mechanism within the plants which reduced the toxic affects from RH 8817 more rapidly than for oxyfluorfen. Another possibility is that oxyfluorfen experienced less hydrogen bonding in the soil solu- tion than RH 8817 thus necessitating less energy for vaporization. RH 8817 may also have been more strongly bound to the organic colloids. This may be a possibility since the two compounds differ only in the substituent group attached at the 3-position of the phenoxy ring, that being an ethoxy group in oxyfluorfen and a carboxyethyl group in RH 8817. The greater polarity of the carboxyethyl group would in- crease the amount of hydrogen bonding in the soil solution or to the organic colloids while the ethoxy group, being less polar, would ex- perience less hydrogen bonding and thus would be more available for vaporization. Soybean Hypocotyl Injury from Diphenylether Herbicides Preemergence applications of diphenylether herbicides have been shown to cause lesion injuries to hypocotyls of several leguminous species with tolerance based on rates of emergence (4). This would suggest that lower day-night temperatures which slow soybean growth rates could also increase hypocotyl injury and subsequently reduce shoot growth. Figures 7A, B, and C show that hypocotyl injury from oxyfluorfen occurred at all rates tested, being observed as varying degrees of stem necrosis. As day-night temperatures decreased injury correspondingly increased such that at the low temperature regime (Figure 7C), injury at rates of 0.56 kg/ha or higher produced hypocotyl 89 injury so severe that few soybean plants were able to emerge. An increase in soil organic matter content significantly reduced injury primarily at the middle temperature regime (Figure 7B) which indicates the rate of growth played a more important role in determining soybean hypocotyl injury than soil organic matter content. Soybean injury from RH 8817 also increased as day-night tempera- tures decreased and as soil organic matter content decreased (Figure 8A, B, and C). A comparison of oxyfluorfen and RH 8817 at the high temperature regime shows less soybean injury from RH 8817 only on the 1.5% OM soil at the 1.12 kg/ha herbicide rate with other herbicide application rates and soil organic matter content levels showing no differences. At the low temperature regime, injury was not signifi- cantly different on the 1.5% and 5.5% OM soils at any rate above 0.56 kg/ha for either herbicide but RH 8817 caused less injury than oxyfluor- fen on the 8.2% OM soil. At the intermediate temperature regime, RH 8817 showed less injury than oxyfluorfen on 1.5% OM soil while on the 5.5% and 8.2% OM soils, no differences in soybean hypocotyl in- jury were found between the two herbicides. These results indicate that oxyfluorfen and RH 8817 do not dif- fer significantly in causing hypocotyl injury to soybean except at the intermediate and low temperature regimes on 1.5% and 8.2% OM soils, respectively. These results are important for soybean producing re- gions such as Michigan where temperatures are often low during soy- bean emergence and where soil organic matter content can vary signi- ficantly within a field. If soybean hypocotyls were injured at emer- gence from diphenylether herbicides, reductions in population densities and soybean seedling vigor could lead to lower yields. 10. 11. 12. 13. 14. 15. 90 LITERATURE CITED Ebner, L., D. H. Green, and P. Pande. 1968. C-6989, a new selec- tive herbicide. Proc. 9th Br. Weed Control Conf. Vol. 2:1026-1032. Fadayomi, 0. and G. F. Warren. 1977a. Adsorption, desorption and leaching of nitrofen and oxyfluorfen. Weed Sci. 25:97-100. Fadayomi, O. and G. F. Warren. 1977b. Uptake and translocation of nitrofen and oxyfluorfen. Weed Sci. 25:111-114. Fadayomi, O. and G. F. Warren. 1977c. Differential activity of three diphenyl ether herbicides. Weed Sci. 25:465-468. Grover, R., W. F. Spencer, W. J. Farmer, and T. P. Shoup. 1978. Triallate vapor pressure and volatilization from glass surfaces. Weed Sci. 26:505-508. Harvey, R. G. 1974. Soil adsorption and volatility of dinitro- aniline herbicides. Weed Sci. 22:120-124. Hayes, R. M. and J. R. Overton. 1979. Comparison of selected diphenylether herbicides for weed control in soybeans. Proc. South. Weed Sci. Soc. 32:69 (Abstr.). Kearney, P. C. and D. D. Kaufman. 1976. Herbicides—-Chemistry, deg- radation and mode of action. Marcel and Dekker, Inc., New York. 1036 pp. Kennedy, J. M. and R. E. Talbert. 1977. Comparative persistence of dinitroaniline type herbicides on the soil surface. Weed Sci. 25:373-381. Miller, S. D. and J. D. Nalewaja. 1976. Phytotoxicity of trial- late vapors to wild oat. Weed Sci. 24:134-136. Mobil Chemical. 1974. MOdown herbicide. Tech. Bul. Parochetti, J. V. and E. R. Hein. 1973. Volatility and photodecom- position of trifluralin, benefin and nitralin. Weed Sci. 21:469-473. Parochetti, J. V., G. W. Dec, Jr., and G. W. Burt. 1976. Volatil- ity of eleven dinitroaniline herbicides. Weed Sci. 24:569-532. Walter, J. P., E. F. Eastin, and M. G. Merkle. 1970. The persis- tence amd movement of fluorodifen in soils and plants. Weed Res. 10:165-171. Yih, R. Y. and C. Swithenbank. 1975. New diphenyl ether herbi- cides. J. Agric. Food Chem. 23:592-593. 91 Table 1. Physical and chemical analysis of soils used in green- house and growth chamber experiments. Mechanical Analysis Organic matter Sand Silt Clay Soil type % Hillsdale sandy clay loam 1.5 55.3 22.0 22.7 Selfridge clay loam 5. 43.0 20.4 36.7 Capac sandy clay loam 8.2 57.5 14.0 24.5 92 Table 2. GRSO values (kg/ha)fkurpreemergence applica- tions of selected herbicides on Datura stramonium L. var. tatula (L.) Torr. and Datura stramonium L. var. stramonium based on visual injury. GR50a var. tatula var. stramonium kg/ha Herbicides Oxyfluorfen 0.58 0.64 RH 8817 0.64 0.66 Alachlor 3.4 3.8 Metolachlor 3.8 4.4 Metribuzin 0.36 0.29 aValues were calculated from linear regression equations for a 50% visual injury rating. 93 Figure 1. Drawing of potting system used to measure injury to soybean and jimsonweed from vapors of oxyfluorfen and RH 8817 treated soil. 94 C D -—-— VAPOR CHIMNEY TR EATM ENT POT — — GROWTH POT 95 Figure 2. Percent visual injury of Datura stramonium L. var. tatula (L.) Torr. from preemergence applications of oxyfluorfen on Hillsdale sandy clay loam soil with 1.5% OM, Selfridge clay loam soil with 5.5% OM, and Capac sandy clay loam soil with 8.2% OM. Plants were grown under greenhouse conditions. 96 123223332er «H.H OOO HOO ORO ««O m H H H _ 8.93 IL. L 1. J 20 0\oN.Q IL 1 so is l 20 o..\om.P L 2 AN on cc cm on ON on ,om .2: AHRI'NI % Figure 3. 97 Percent visual injury to Datura stramonium L. var. tatula (L.) Torr. from preemergence applications of RH 8817 on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% 0M, and Capac sandy clay loam soil with 8.2% OM. Plants were grown under greenhouse conditions. 98 NPH omd €59: HHOO z: HOO med Nwé - 1H HOOOOH .20 o\oN.m 5.0 o\om.m H \ 5.0 o\om.quI Hr Op 18 [COO 110m low [as 1am 169.. A811le °/o Figure 4. 99 Comparison of the visual injury to Datura stramonium L. var. tatula (L.) Torr. from preemergence applica- tions of oxyfluorfen and RH 8817 on Selfridge clay loam soil with 5.5% OM. Plants were grown under greenhouse conditions. lOO Nwé omd HOO mOHOO med NNd 3.3.. tow Imul Zwu1034m>x0 H uH low low .los .I. cow AHI'H‘NI °/o Figure 5. 101 Comparison of the visual injury to Datura stramonium L. var. tatula (L.) Torr. from vapors of oxyfluorfen and RH 8817 from preemergence applications to sandy clay loam soils with either 1.5% or 8.2% organic mat- ter contents and which were brought to field capacity once daily. 3. 1.5% OM soil is abbreviated as LOMC (low organic matter content). b. 8.2% 0M soil is abbreviated as HOMC (high organic matter content). 102 mm. OOHOH O«. 05.0.... spam I: 05.01 Zmum034u>x0 A 05.0.. tau :1 0.20.. Zmum034u>x0 H33. or ON on av cm cm on an cm 00.. AURI‘NI % 103 Figure 6. Comparison of the visual injury to soybean [Glycine .E§§ (L.) Merr.] from vapors of oxyfluorfen and RH 8817 from preemergence applications to sandy clay loam soils with either 1.5% or 8.2% organic matter contents and which were brought to field capacity once daily. a. 1.5% OM soil is abbreviated as LOMC (low organic matter content). b. 8.2% OM soil is abbreviated as HOMC (high organic matter content). 104 OOHOH s«..« 8.. «H.H 3O 8.3. 020. . spam I". 020.... . tan :1 020... zmum0:.n.>x0 020.. Zmum0:.n.>x0 4o? L.O« u... AHOI‘NI °/o Figure 7. 105 Visual injury ratings for soybean hypocotyls follow- ing preemergence applications of oxyfluorfen on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% OM, and Capac sandy clay loam soil with 8.2% OM. Plants were grown under three separate day-night temperature regimes. A. 29 C-day and 18 C-night B. 24 C-day and 13 C-night C. 18 C-day and 7 C-night 106 2.x... :3 z: 36 cud H AUM'N' '19 23.. H8. 2.. .0 in; .3..qu 3.0! O ' 88283388 ' AII'II'II 95 11.702 Feuueu lllllll L Allflfm % Figure 8. 107 Visual injury ratings for soybean hypocotyls follow- ing preemergence applications of RH 8817 on Hillsdale sandy clay loam soil with 1.5% 0M, Selfridge clay loam soil with 5.5% OM, and Capac sandy clay loam soil with 8.2% OM. Plants were grown under three separate day-night temperature regimes. A. 29 C-day and 18 C-night B. 24 C-day and 13 C-night C. 18 C-day and 7 C-night 108 2.3.. to. :c 3.6 H and — “"1le ".o of... HS. 2.. 3... ‘IIan Canons AUflle °~ LllJ ow on 11411 e AUM‘NI °e CHAPTER 5 FATE OF 14C-RH 8817 AND 1l‘C-OXYFLUORFEN FROM HYPOCOTYL APPLICATIONS TO SOYBEAN [GLYCINE MAX (L.) MERR. 'HAROSOY 63'] AND JIMSONWEED [DATURA STRAMONIUM L. VAR. TATULA (L.) TORR.] ABSTRACT Translocation and metabolism studies were conducted with hypo- cotyl applications of 14C-RH 8817 [2-chloro-l-(3-carboxyethy1-4- nitrophenoxy)-4-(trifluoromethyl)benzene] and 14C-oxyfluorfen [2- chloro-l-(3-ethoxy-4-nitrophenoxy-4-(trifluoromethyl)benzene] to soybean [Glycine max (L.) Merr. 'Harosoy 63'] and jimsonweed [Datura stramonium L. var. tatula (L.) Torr.]. After 1 day, 7.6% of the 14C from both 14C-herbicides was found in soybean plant parts above the hypocotyl with negligible basipetal movement and 89% of the 14C re- mained at the site of application. After 3 days, 7.0% and 6.7% of 14C-RH 8817 and 14C-oxyfluorfen, respectively, were found in var. tatula plant parts above the hypocotyl and 89.4% and 86.1% of the 14C remained in the hypocotyl with negligible basipetal movement. Metabolism stud- ies indicated soybean plants degraded 14C-RH 8817 at a faster rate than 1l'C-oxyfluorfen with 33.2% and 30.8% of each herbicide, respec- tively, found in the acetone-insoluble plant residue of the hypocotyl after 1 day while 77.0% and 58.7% were found after 12 days. Less soy- bean hypocotyl injury may be related to a faster rate of metabolism of RH 8817 than oxyfluorfen. Rapid metabolism was also found 3 days after 109 110 application in var. tatula with 71.53% and 67.7% of the radioactivity in the hypocotyl being detected in the acetone-insoluble residue from applications of 14C-RH 8817 and 14C-oxyfluorfen, respectively. The translocated 14C was also found primarily in the acetone-insoluble plant residue. The remaining radioactivity at the site of application in the hexane-soluble fraction from both soybean and var. tatula was identified by Thin Layer Chromatography (TLC) as the applied parent compound with no acifluorfen or p-nitrophenol detected. 111 INTRODUCTION Selectivity between susceptible and tolerant plant species and differential sensitivity to similar herbicides is often based on dif- ferential adsorption, translocation, and metabolism. Several diphenyl- ether herbicides have been found to cause injury to plant species that translocated the herbicides from the roots while not damaging others in which translocation did not occur (1, 2, 4, 8, 10, 13). Metabolism of diphenylether herbicides has also been found as a mechanism for selectivity (3, 9) with glutathione-S-transferase cleaving the ether linkage and forming water-soluble conjugates (11). Studies with oxy- fluorfen have shown little translocation or metabolism occurred from foliar or root applications to either tolerant or susceptible species (6, 12). Phytotoxicity to sorghum seedlings [Sorghum bicolor (L.) Moench] was found to occur primarily from shoot uptake (5) while in- jury to hypocotyls of four leguminous species was found to increase with a decreased rate of plant growth (7). Since oxyfluorfen is pri- marily soil applied and diphenylether herbicides generally do not leach into the root zone (6) but rather are active on emerging plant shoots, studies were initiated to examine the fate of diphenylether herbicides from hypocotyl application. ll'C-RH 8817 and 1l'C-oxyfluorfen were ap- plied with microsyringe techniques to soybean and jimsonweed seedling hypocotyls to examine translocation and metabolism differences between the two herbicides and between the two plant species. 112 MATERIALS AND METHODS Cultural Practices Both soybean and Datura stramonium L. var. tatula (L.) Torr. were grown in growth chambers under a fluorescent lighting regime of 350 uE m-2 sec-1 under a 16 h photoperiod with temperatures of 29 C- day and 18 C-night and 70% relative humidity. Four 'Harosoy 63' soy- bean or 16 var. tatula seeds were planted in 480 ml double wax paper cups containing sandy clay loam soil with 57.52 sand, 14.0% silt, 24.5% clay, and 8.2% organic matter. Plants were subirrigated once daily with tap water. 1l‘C-Herbicide Application Translocation and metabolism studies were conducted with 14C- 1(’CnRH 8817 (10.11 uCi/mg). 1[‘C- oxyfluorfen (2.61 uCi/mg) and acifluorfen (1.33 uCi/mg) was evaluated as a possible metabolite of RH 8817 and unlabeled p-nitrophenol was also co-chromatographed as a possible metabolite of both 14C-herbicides. All 14C-herbicides were uniformly labeled in the nitrophenyl ring. Radiolabeled herbicides were applied with 10 ul syringes fitted to Hamilton repeating dispen- sers. Five ul of a 200 ug/ul methanol solution of each herbicide was applied to soybean hypocotyls 5 days after emergence. Five ul of a 50 ug/ul methanol solution of each herbicide was applied to var. tatula hypocotyls 7 days after emergence. Sample Handlingiand Extraction Procedures Four soybean plants per replication of each herbicide treatment were harvested 1, 3, 6, and 12 days after application. Plants were 113 sectioned into roots, hypocotyl, cotyledons, and the stem and leaflets above the cotyledons (shoot above). Sixteen var. tatula plants per replication of each herbicide treatment were harvested 3 and 6 days after application. Plants were sectioned into roots, hypocotyl, and plant material above the hypocotyl (shoot above). Each plant section of both species was homogenized in 15 ml of acetone for 5 min and vacuum filtered through glass microfiber filter paper. The acetone-insoluble plant residue was air-dried, weighed, and combusted in a Harvey 0X-200 oxidizer and resultant 14CO2 was trapped in 15 ml of Permaflour V: Carbosorb II (2:1, v/v). The acetone filtrate was taken to dryness in SO-ml round bottom flasks at 35 C under vacuum. Flasks were rinsed with two aliquots of hexane (2.0 ml) and distilled water (2.0 m1) and poured into 30-m1 separatory funnels. The fractions were separated and placed in 12-ml graduated test tubes and brought up to a volume of 5 ml with the respective diluent. A 1.0 ml aliquot was removed from each fraction and added to 10 ml of ACS (Aqueous Counting Solution) (Amersham Corp., Arlington Heights, 111.). All samples were quantified for radioactivity by liquid scintillation spectrometry and corrected for quenching by external standardization. Thin Layer Chromatography Aliquots of 100 ul of the hexane-soluble fraction from hypocotyl sections of both soybean and var. tatula from each harvest time were spotted on LKSD Linear-K silica gel plates (Whatman Inc., Clifton, NJ). 14 14 14 Standards of C-oxyfluorfen, C—RH 8817, C-acifluorfen, and p- nitrophenol were co-chromatographed with the samples. TLC plates were devel- oped with toluene, n-hexane, and methanol (60:40:5, v/v/v). A Berthold 114 LB 276 TLC scanner and radioautographic plates were used to locate radioactive Spots. Statistical Considerations Both soybean and var. tatula experiments were analyzed as 2 by 2 factorials with a split for time in a completely randomized block design with eight replications. Data for each experiment were sub- jected to analysis of variance and mean separation by Duncan's multiple range test. RESULTS AND DISCUSSION Translocation and Metabolism in Soybean Translocation of 14C-RH 8817 following application to soybean hypocotyls (Table 1) indicated that after 24 h, 7.6% of the radioac— tivity detected has moved acropetally while 89% of the 140 remained at the site of application. After 12 days, the amount of radioactivity found in plant parts above the site of application had not changed nor had the amount found in the hypocoytl. Basipetal transport of 14C from 1l’C-RH 8817 was negligible during the entire course of the exper- iment. Translocation of 14C from 1I‘C-oxyfluorfen from soybean hypo- cotyls was also primarily acropetal with a maximum of 7.6% of the 14C found in plant parts above the site of application after 12 days while 88.7% of the 14C remained in the hypocotyl. Basipetal transport of 14C was also negligible. Metabolism of both 14C—RH 8817 and 14C-oxyfluorfen occurred with- in 24 h after application to shoot hypocotyls and continued over the course of the study. Radioactivity from 14C-RH 8817 detected in the 115 acetone-insoluble residue of the hypocotyl after 1, 3, 6, and 12 days was 33.2%, 50.3%, 64.0%, and 77.0%, respectively. Examination of the hexane fraction by thin layer chromatography indicated that the major portion of the radioactivity present was 14C-RH 8817 (Figure 1). Con- version of 14C-RH 8817 to 1[.C-acifluorfen by cleavage of the ethyl portion of the carboxyethyl substituent was not detected since no peak with corresponding Rf value similar to 14C-acifluorfen was found in all hypocotyl hexane-soluble fractions examined. No p-nitrophenol, another possible metabolite, was found from TLC examination of hexane- soluble fractions from the hypocotyl. After 24 h only 0.5% of the applied radioactivity was detected as 14C-RH 8817 in the hexane-soluble fraction of the shoot portion above the hypocotyl and cotyledons while 3.2% was found in the acetone- insoluble residue. No radioactivity was found in the hexane-soluble fraction after 3, 6, and 12 days indicating no further translocation after the initial herbicide treatment. Any visual injury to soybean foliage from soil application of RH 8817 therefore may not be from herbicide movement from the hypocotyl to shoot. Metabolism in the hypocotyl of 1l‘C-oxyfluorfen was also found to occur with 30.8%, 42.3%, 52.4%, and 58.7% of the radioactivity detected in the acetone-insoluble plant residue after 1, 3, 6, and 12 days, respectively. Thin layer chromatography indicated the hexane-soluble fraction from the hypocotyl contained primarily 14C-oxyfluorfen (Figure 2). In the shoot portion above the site of application, most of the radioactivity was detected in the acetone-insoluble plant residue, again indicating translocation from the hypocotyl was not a major source of injury to soybean foliage. 116 A comparison of the percentages of radioactivity found in the acetone-insoluble plant residue after 1 and 12 days indicated soybean plants metabolized 3.2% and 18.3%, respectively, of the 14C-RH 8817 and 14C-oxyfluorfen. This difference may explain why soybean plants are less sensitive to preemergence applications of RH 8817 than to oxyfluorfen. Translocation and Metabolism in var. tatula Movement of 14C-RH 8817 from var. tatula hypocotyls was primarily acropetal with only 8.6% of the radioactivity found in the shoot por- tion above the site of application 6 days after treatment (Table 2). Translocation was limited since 88.0% of the radioactivity was detected at the site of application. Movement of l[‘C-oxyfluorfen was also ac— ropetal with 8.5% of the radioactivity found in the shoot while 85.3% remained at site of application 6 days after treatment. Am examination by TLC of the hexane-soluble fraction from the hypocotyl section indi- cated that most of the radioactivity remaining was present as the re— spective parent compound. No peaks were found which corresponded with 14C-acifluorfen or p-nitrophenol. Metabolism of both herbicides occurred very rapidly with 71.5% and 67.7% of 14C-RH 8817 and 14C-oxyfluorfen, respectively found in the acetone-insoluble plant residue of the hypocotyl 3 days after treat- ment. Metabolism of translocated ll‘C-RH 8817 and 14C-oxyfluorfen also occurred in the shoot with 8.5% and 8.7% of each herbicide, respectively, found in the acetone-insoluble plant residue with no significant amount of radioactivity remaining in the hexane-soluble fraction. 10. ll. 12. 117 LITERATURE CITED Eastin, E. F. 1969. Movement and fate of p—nitrophenyl-a,a,a- trifluoro-Z-nitro—p tolyl ether-1'-14C in peanut seedlings. Plant Physiol. 44:1397-1401. Eastin, E. F. 1971a. Movement and fate of f1uorodifen-l'-14C in cucumber seedlings. Weed Res. 11:63-68. Eastin, E. F. 1971b. Fate of fluorodifen in resistant peanut seedlings. Weed Sci. 19:261-265. Eastin, E. F. 1972. Fate of fluorodifen in susceptible cucumber seedlings. Weed Sci. 20:255-260. Fadayomi, 0. and G. F. Warren. 1977a. Adsorption, desorption and leaching of nitrofen and oxyfluorfen. Weed Sci. 25:97-100. Fadayomi, 0. and G. F. Warren. 1977b. Uptake and translocation of nitrofen and oxyfluorfen. Weed Sci. 25:111-114. Fadayomi, 0. and G. F. Warren. 1977c. Differential activity of three diphenyl ether herbicides. Weed Sci. 25:465-468. Leather, G. R. and C. L. Foy. 1978. Differential absorption and distribution as a basis for the selectivity of bifenox. Weed Sci. 26:76-81. Locke, R. K. and R. L. Baron. 1972. Preforan metabolism by tobacco cells in suspension culture. J. Agric. Food Chem. 20:861-867. Rogers, R. L. 1971. Absorption, translocation and metabolism of p-nitrophenyl-a,a,o-trifluoro-Z-nitro-p-tolyl ether by soybeans. J. Agric. Food Chem. 19:32-35. Shimabukuro, R. H., G. L. Lamoureux, H. R. Swanson, W. C. Walsh, L. E. Stafford, and D. S. Frear. 1973. Metabolism of substituted diphenylether herbicides in plants. 11. Identification of a new fluorodifen metabolite, S-(2-nitro-4-trifluoromethylphenyl)- glutathione in peanut. Pest. Biochem. and Physiol. 3:483-494. Vanstone, D. E. and E. H. Stobbe. 1978. Root uptake, transloca- tion and metabolism of nitrofluorfen and oxyfluorfen by fababeans (Vicia faba) and green foxtail (Setaria viridis). Weed Sci. 26: 389-392. 118 .munnaa cnwnmom mm mo chfiuomm Han mo coauunuw manaaomluwuna can .aowuonum mannaomloanxos .oswfimou uano wHQDHOmCHImaOumon Eouw znw nonm co owfiownuon nunm you 0mum>oumu >uw>fiuonowvnu mo unseen HnuOu mnu no vomnn mmwnucmouwm n .umnu owcnu oHaHuass m.onossn ou wawouooon Hw>oH Nm mso un quHmMMHw kHanofiwwcwwm uoc mun Houuma mEnm mau ha wosofiaom hnw nonm How cnmE hon cmeumn comfiunanon m00.m no.0 nn0.N nm.o wo~.N n~.0 onnm.H n~.0 m>opn uoonm wm0.m nn~.0 nnm.~ onm.0 ww.~ onnw.o onnm.H onnm.H cowoamuou fi~.wm no.0m mq.~m nm.am mm.~q sm.mq wm.om mm.Ho asuouoasm wonw.H an0.0 nnn.o nnm.H onn0.0 nn0.0 nn0.0 onnm.H uoom somuosam%xo n00c.~ no.0 nn0.q no.0 m0.q no.0 onm.m nnm.0 o>onn uoozm MH.m nH.0 no.m nN.0 m~.m nm.0 om.m nq.0 aovoa>uou xo.wn mq.mH m0.qo om.HN :m.0m me.nm om.mm mw.mm Hhuoooomm nnm.0 no.0 nm.0 no.0 nm.0 nH.o nnm.o nnm.o uoom mama mm coauoom uanHm nwauwnumm osvfimou :ofiuunum nswfimmu aowuonuw osvfimou aoHuonum uncanny coauonum mapaaomcH ocnxom wannaomcH manxom manaaomaH manxom nansaomcH manxmm wwwo NH mmno 0 mNma m coaunowanan known mhna n.mH%uooon%: anmp>ow ou coaunofiaamn umumn mhnw «H van .0 .m .H anwuosammxolo van mama mmlo mo amfiaonnuna van cowunooamanus .H manna «a «H 119 Table 2. Translocation and metabolism of 14C-RH 8817 and 14C— oxyfluorfen 3 and 6 days after application to hypocotyls of Datura stramonium L. var. tatula (L.) Torr. seedlings.a Days after application 3 Days 6 Days Hexane Insoluble Hexane Insoluble fraction residue fraction residue Herbicide Plant section %b RH 8817 Root 0.2a 0.4a 0.2a 0.53 Hypocotyl 17.9c 71.5e 9.5bc 78.4e Shoot above 1.1a 6.4b 0.03 8.5b Goal Root 0.8a 2.3a 0.63 2.63 Hypocotyl 18.4c 67.7d 11.4c 73.9d Shoot above 0.0a 6.7b 0.3a 8.5b 8Comparison between any mean for each day followed by the same letter are not significantly different at the 5% level according to Duncan's multiple range test. bPercentage based on total amount of radioactivity recovered for each herbicide on each day from acetone—insoluble plant residue, hexane- soluble fraction, and water-soluble fraction of all sections of 128 var. tatula plants. 120 Figure 1. Radioscans of thin-layer chromatograms from the hexane- soluble fraction from soybean hypocotyl 1 and 12 days after application of 1l‘C-—RH 8817. TLC plates were developed in toluene:n—hexanezmethanol (60:40:5, v/v/v). Rf values for 14C-RH 8817, 14C-acifluorfen, and p- nitrophenol were 0.58, 0.08, and 0.1, respectively. CPM X 200 CPM X 200 10 121 14 DAY 1 C—RH 8817 K A ”A A. .L in AA. ‘ “.1 LA .4 4‘ .‘u .u h .11, I 0.59 DAY 12 Rf VALUES 0.57 R VALUES f Figure 2. 122 Radioscans of thin-layer chromatograms from the hexane- soluble fraction from soybean hypocotyl 1 and 12 days after application of 14C—oxyfluorfen. TLC plates were developed in toluene:n—hexanezmethanol (60:40:5, v/v/v). R values for 14C-oxyfluorfen and p—nitro— f phenol standards were 0.64 and 0.1, respectively. CPM X 200 CPM X 200 10 U1 10 123 A DAY 1 1 (T—OXYFLUURFFN I 0.67 Rf VALUES DAY 12 0.64 Rf VALUES APPENDICES 124 Appendix A. Effect of shallow incorporationa treatments of oxyfluorfen or RH 8817 applied alone or in com- bination with alachlor or metribuzin on Datura stramonium L. var. tatula (L.) Torr. Planting occurred on June 28, 1980 at Location 11 on Whitaker sandy clay loam soil with 4.1% organic matter content.b Control of var. tatula Rate 4 weeks 12 weeks Treatment (kg/ha) -—----— Oxyfluorfen 0.56 77 d-g 10 ab 0.84 80 d-g 40 be 1.12 88 fg 40 be RH 8817 0.56 87 efg 43 bcd 0.84 87 efg 50 cde 1.12 78 d-g 57 c-f 1.40 97 g 98 g Oxyfluorfen + alachlor 1.12 + 2.24 97 g 97 g 1.12 + 3.36 98 g 100 g RH 8817 + alachlor 1.12 + 2.24 98 g 97 g 1.40 + 2.24 95 g 97 g 1.12 + 3.36 92 fg 93 fg 1.40 + 3.36 100 g 83 d-g Oxyfluorfen + metribuzin 0.84 + 0.56 98 g 80 d-g RH 8817 + metribuzin 0.84 + 0.56 95 g 72 c-g 1.12 + 0.56 98 g 90 fg Untreated control 0.0 0 a 0 a aA rotary hoe was used for shallow incorporation of herbicides to an approximate depth of 1.25 cm immediately following application. bMeans followed by the same letter are not significantly different at the 5% level according to Duncan's multiple range test. Appendix C. Concentration of 14C-RH 8817 (10.11 uCi/mg) and 4C-oxyfluorfen (2.61 pCi/mg) in various plant sections following hypocotyl application of 0.25 mg per plant of each herbicide after 3 and 6 days.8 Days after application 3 Days §_Dgy§ Herbicide Plant Section -——-———— ug/g ——-—————— RH 8817 Root 0.33 a 0.01 a Hypocotyl 13.67 b 6.14 ab Shoot above 0.11 a 0.1 a Oxyfluorfen Root 0.0 a 0.09 a Hypocotyl 13.44 b 37.32 c Shoot above 0.34 a 0.72 a aMeans followed by the same letter are not significantly different at the 5% level according to Duncan's multiple range test. BIBLIOGRAPHY BIBLIOGRAPHY Agaev, M. G. 1974. Population density as a regulatory factor of plant development. Dokl. Akad. Nauk. Sssr. Ser. Biol. 217: 705-708. (In Russian.) Avery, A. C., S. Satina, and J. Rietsema. 1959. Blakeslee: The genus Datura. Ronald Press, New York. 289 pp. Barrentine, W. L. 1974. Common cocklebur competition in soybeans. Weed Sci. 22:600-603. Bateson, W. and E. R. Saunders. 1902. Experimental studies in the physiology of heredity. Datura Reports to the Evolution Com- mittee of the Royal Soc. Beverley, R. 1705. The history and present state of Virginia.. Republished for Inst. of Early Am. Hist. and Cul. at Williamsburg, Va. Univ. N. C. Press, 1947. Black, C. C., T. M. Chen, and R. H. Brown. 1969. Biochemical basis for plant competition. Weed Sci. 17:338-344. Bohn, J. A. and C. E. Rieck. 1979. The activity of diphenyl ethers on chloroplast. Proc. South. Weed Sci. Soc. 32:323 (Abstr.). Buchanan, G. A. and E. R. Burns. 1971. Weed competition in cotton. 1. Sicklepod and tall morningglory. Weed Sci. 5:576-582. Buchanan, G. A., C. S. Hoveland, and M. C. Harris. 1975. Response of weeds to soil pH. Weed Sci. 23:473-477. Bugg, M. W., J. Whitmarsh, C. E. Rieck, and W. S. Cohen. 1980. In- hibition of photosynthetic electron transport by diphenyl ether herbicides. Plant Physiol. 65:47—50. Chesnut, V. K. 1898. Principal poisonous plants of the United States. USDA Bulletin No. 20. 60 pp. Crockett, L. J. 1977. Wildly successful plants. Macmillan Pub. Inc., New York. 286 pp. Crowley, R. H. and G. A. Buchanan. 1978. Competition of four morn— ingglory (Ipomoea spp.) species with cotton (Gossypium hirsutum). Weed Sci. 26:484-488. 127 128 Debourcieu, L. 1977. Application of thin layer electro-focusing to the chemotaxonomy of the genus Datura (Solanaceae). Plant Med. Phytother. 11:12-15. Eastin, E. F. 1969. Movement and fate of o-nitrophenyl-a,a,a-tri- fluoro-Z-nitro-o tolyl ether-1'-14C in peanut seedlings. Plant Physiol. 44:1397-1401. Eastin, E. F. 1971a. Movement and fate of f1uorodifen-l'-14C in cucumber seedlings. Weed Res. 11:63-68. Eastin, E. F. 1971b. Degradation of f1uorodifen-1'-14C by peanut seedling roots. Weed Res. 11:120-123. Eastin, E. F. 1971c. Fate of fluorodifen in resistant peanut seed- lings. Weed Sci. 19:261-265. Eastin, E. F. 1972. Fate of fluorodifen in susceptible cucumber seedlings. Weed Sci. 20:255-260. Ebner, L., D. H. Green, and P. Pande. 1968. C-6989: a new selec- tive herbicide. Proc. 9th Br. Weed Control Conf. Vol. 2: 1026-1032. Erdman, W. and M. W. Emmel. 1950. Some poisonous plants in Florida. Univ. of Fla. Bul. 468. 47 pp. Fadayomi, O. and G. F. Warren. 1976. The light requirement for herbicidal activity of diphenyl ethers. Weed Sci. 24:598-600. Fadayomi, 0. and G. F. Warren. 1977a. Adsorption, desorption and leaching of nitrofen and oxyfluorfen. Weed. Sci. 25:97-100. Fadayomi, 0. and G. F. Warren. 1977b. Uptake and translocation of nitrofen and oxyfluorfen. Weed Sci. 25:111-114. Fadayomi, O. and G. F. Warren. 1977c. Differential activity of three diphenyl ether herbicides. Weed Sci. 25:465-468. Frazee, R. W. and E. W. Stoller. 1974. Differential growth of corn, soybean, and seven dicotyledonous weed seedlings. Weed Sci. 22: 336-339. Frear, D. S. and H. R. Swanson. 1973. Metabolism of substituted diphenylether herbicides in plants. Enzymatic cleavage of fluor- odifen in peas. Biochem. Physiol. 3:473-482. French, C. M. and P. W. Santelmann. 1976. Phytotoxicity and soil activity of RH 2915. Proc. South. Weed Sci. Soc. 29:407 (Abstr.). Gleason, H. A. and A. Cronquist. 1968. Manual of vascular plants of northeastern United States and adjacent Canada. Van Nostrand Reinhold Co., New York. 810 pp. 129 Gorske, S. F. and H. J. Hopen. 1978. Effects of two diphenylether herbicides on common purslane (Portulaca oleracea). Weed Sci. 26:585-588. Grover, R., W. F. Spencer, W. J. Farmer, and T. D. Shoup. 1978. Triallate vapor pressure and volatilization from glass surfaces. Weed Sci. 26:505-508. Hardin, J. W. and J. M. Arena. 1974. Human poisoning from native and cultivated plants. Duke Univ. Press, Durham, N. C. 167 pp. Harvey, R. G. 1974. Soil adsorption and volatility of dinitroan- iline herbicides. Weed Sci. 22:120-124. Hawton, D. and E. H. Stobbe. 1971. Selectivity of nitrofen among rape, redroot pigweed, and green foxtail. Weed Sci. 19:42-44. Hayes, R. M. and J. R. Overton. 1979. Comparison of selected di- phenylether herbicides for weed control in soybeans. Proc. South. Weed Sci. Soc. 32:69 (Abstr.). Holm, L., J. V. Pancho, J. P. Herberger, and D. L. Plucknett. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp. Holm, L., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The world's worst weeds. Distribution and biology. Univ. Press of Hawaii, Honolulu. 609 pp. Holm, R. E. and M. R. Miller. 1972a. Weed seed germination responses to chemical and physical treatments. Weed Sci. 20:150-153. Holm, R. E. and M. R. Miller. 1972b. Hormonal control of weed seed germination. Weed Sci. 20:209-212. Hoveland, C. S., G. A. Buchanan, and M. C. Harris. 1976. Response of weeds to soil phosphorus and potassium. Weed Sci. 24:194-201. Johnson, W. 0., G. E. Kollman, C. Swithenbank, and R. Y. Yih. 1978. RH 6201 (Blazer): A new broad spectrum herbicide for postemergence use in soybeans. J. Agric. Food Chem. 26:285. Jordan, T. N. 1979. 1979 Extension county agent weed survey of problem weeds in Indiana. Purdue Univ., West Lafayette, Ind. 20 pp. Kearney, P. C. and D. D. Kaufman. 1976. Herbicides--Chemistry, degrada- tion and mode of action. Marcel and Dekker, Inc., New York. 1036 pp. Kennedy, J. M. and R. E. Talbert. 1977. Comparative persistence of dinitroaniline type herbicides on the soil surface. Weed Sci. 25: 373-381. Leather, G. R. and C. L. Foy. 1978. Differential absorption and dis- tribution as a basis for the selectivity of bifenox. Weed Sci. 26:76-81. 130 Lewis, W. H. and M. P. F. Elvin-Lewis. 1977. Medical botany. Plants affecting man's health. John Wiley & Sons, New York. 515 pp. Locke, R. K. and R. L. Baron. 1972. Preforan metabolism by tobacco cells in suspension culture. J. Agric. Food Chem. 20:861-867. Mangeot, B. L. 1978. Activity and selectivity of acifluorfen. Ph.D. dissertation. Univ. of Kentucky, Lexington, Ky. 101 pp. Mathis, W. D. and L. R. Oliver. 1975. Effects of bentazon on dif- ferent weed species at various stages of growth. Proc. South. Weed Sci. Soc. 28:35 (Abstr.). Matsunaka, S. 1969a. Activation and inactivation of herbicides by higher plants. Residue Rev. 25:45-58. Matsunaka, S. 1969b. Acceptor of light energy in photoactivation of diphenylether herbicides. J. Agric. Food Chem. 17:171-175. McGlamery, M. D. 1975. 27th annual Illinois custom spray operators training school. Univ. of 111., Urbana-Champaign. 141-148. McWhorter, C. G. and J. M. Anderson. 1979. Hemp sesbania (Sesbania exaltata) competition in soybeans (Glycine max). Weed Sci. 27: 58—64. Meggitt, W. F. 1980. Weed control guide for field crops. Mich. State Univ. Ext. Bul. E-434. Coop. Ext. Serv., Mich. State Univ., East Lansing, Mi. 27 pp. Michigan agricultural statistics. 1977. Mich. Agr. Reporting Ser. Lansing, Mi. 64 pp. Michigan agricultural statistics. 1980. Mich. Agr. Reporting Ser. Lansing, Mi. 80 pp. Mikolich, J. R., G. W. Paulson, and C. J. Cross. 1975. Acute anti- cholinergic syndrome due to Jimson seed ingestion: Clinical and laboratory observation in six cases. Ann. Intern. Med. 83: 321-325. Miller, S. D. and J. D. Nalewaja. 1976. Phytotoxicity of triallate vapors to wild oat. Weed Sci. 24:134-136. Mobil Chemical. 1974. Modown herbicide. Tech. Bul. Moreland, D. E., W. J. Blackmon, H. G. Todd, and F. S. Farmer. 1970. Effects of diphenylether herbicides on reactions of mitochondria and chloroplasts. Weed Sci. 18:636-642. Parochetti, J. V. 1975. Control of jimsonweed and three broadleaved weeds in soybeans with herbicides. Proc. Northeast. Weed Sci. SOC. 29:19-25. 131 Parochetti, J. V., G. W. Dec, Jr., and G. W. Burt. 1976. Volatility of eleven dinitroaniline herbicides. Weed Sci. 24:529-532. Parochetti, J. V. and E. R. Hein. 1973. Volatility and photodecom- position of trifluralin, benefin and nitralin. Weed Sci. 21: 469-473. Pereira, J. F., W. E. Splittstoesser, and H. J. Hopen. 1971a. Mechanism of intraspecific selectivity of cabbage to nitrofen. Weed Sci. 19:647-651. Pereira, J. F., W. E. Splittstoesser, and H. J. Hopen. 1971b. Re- sponse of plant tissues to nitrofen. Weed Sci. 19:662-666. Pollak, T. and G. Crabtree. 1976. Effect of light intensity and quality on toxicity of fluorodifen to green bean and soybean seedlings. Weed Sci. 24:571-573. Rogers, R. L. 1971. Absorption, translocation and metabolism of p-nitrophenyl-a,a,a-trifluoro-Z-nitro-p-toly1 ether by soybeans. J. Agric. Food Chem. 19:32-35. Safford, W. E. 1920. Daturas of the old world and new. An. Rep. Smith. Inst. Publ. 2644:537-567. Schultes, R. E. and A. Hofmann. 1980. The botany and chemistry of hallucinogens. Charles C. Thomas Pub., Springfield, 111. 437 pp. Shimabukuro, R. H., G. L. Lamoureux, H. R. Swanson, W. C. Walsh, L. E. Stafford, and D. S. Frear. 1973. Metabolism of substituted diphenylether herbicides in plants. 11. Identification of a new fluorodifen metabolite, S-(2-nitro-4-trifluoromethylphenyl)- glutathione in peanut. Pest. Biochem. and Physiol. 3:483-494. Smith, T. S. and E. M. Rahn. 1972. Growth and development of jim- sonweed as affected by certain environmental factors. Abstr. Weed Sci. Soc. Am.,;n 23. Sommerville, D. N. and L. M. Wax. 1971. Influence of incorporation depth on chloramben activity. Weed Sci. 19:394-397. Southern Weed Science Society. 1980. Weed Science: The tie that binds, bends. Res. Rep. 33:1-243. Stearn, W. T. 1957. An introduction to the Species Planatarium and conjugate botanical work of Carl Linnaeus. Bartholomew Press. Stoller, E. W. and L. M. Wax. 1973. Periodicity of germination and emergence of some annual weeds. Weed Sci. 21:574-580. Stoller, E. W. and L. M. Wax. 1974. Dormancy changes and fate of some annual weed seeds in the soil. Weed Sci. 22:151-155. 132 Stroube, E. W. 1980. Personal communication. Toole, E. H. and E. Brown. 1946. Final results of the Duvel buried seed experiment. J. Agric. Res. 72:201-210. Torrey, J. 1824. Catalogue of plants of New York. 160 pp. United States Department of Agriculture. 1970. Selected weeds of the United States. Agriculture Handbook No. 366. 463 pp. United States Department of Agriculture. 1972. Extent and cost of weed control with herbicides and an evaluation of important weeds, 1968. ARS-H-l. 227 pp. Vanstone, D. E. and E. H. Stobbe. 1978. Root uptake, translocation and metabolism of nitrofluorfen and oxyfluorfen by fababeans (Vicia faba) and green foxtail (Setaria viridis). Weed Sci. 26:389-392. Vanstone, D. E. and E. H. Stobbe. 1979. Light requirement of the diphenylether herbicide oxyfluorfen. Weed Sci. 27:88-91. Walter, J. P., E. F. Eastin, and M. G. Merkle. 1970. The persistence and movement of fluorodifen in soils and plants. Weed Res. 10: 165-171. Wax, L. M. 1977. Incorporation depth and rainfall on weed control in soybeans with metribuzin. Agron. J. 69:107-110. Wilson, H. P. and R. H. Cole. 1966. Morning glory competition in soybeans. Weeds 14:49-51. Yih, R. Y. and C. Swithenbank. 1975. New potent diphenyl ether herbicides. J. Agric. Food Chem. 23:592-593.