H mm; ill" Ll ll 1|! l Ill Ill Wall II ‘ This is to certify that the thesis entitled HERBICIDAL EFFICACY AND PHYSIOLOGICAL ASPECTS OF GLYPHOSATE [N- (PHOSPHONOMETHYL) GLYCINE] ON FIELD BINDWEED (CONVOLVULUS ARVENSIS L. presented by Curtis Lloyd Sandberg has been accepted towards fulfillment of the requirements for Ph.D. degree in Crop & Soil Sciences l l Major professor ‘3 A Date /- 7'2- A ? 0-7539 HERBICIDAL EFFICACY AND PHYSIOLOGICAL ASPECTS OF GLYPHOSATE [N7(PHOSPHONOMETHYL)GLYCINE] ON FIELD BINDWEED (CONVOLVULUS ARVENSIS L.) BY Curtis Lloyd Sandberg 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 1978 ABSTRACT HERBICIDAL EFFICACY AND PHYSIOLOGICAL ASPECTS OF GLYPHOSATE [N:(PHOSPHONOMETHYL)GLYCINE] ON FIELD BINDWEED (CONVOLVULUS ARVENSIS L.) BY Curtis Lloyd Sandberg Postemergence applications of glyphosate [Nf(phosphonomethy1) glycine] effectively controlled field bindweed when applied at rates of 1.12 kg/ha and above. An additional application of glyphosate after the second season is necessary for continuous field bindweed control. Glyphosate applications can be made anytime after flower bud initiation through late fall. Tillage prior to treatment with gly- phosate reduced field bindweed control and caused proliferation of buds at the nodes of crowns, roots, rhizomes, and stems. Tillage after treatment improved glyphosate performance when the initial control was poor. Glyphosate was not as effective on field bindweed growing on muck soils as on mineral soils. Applications of glyphosate prior to navy beans or following wheat appears to be the most effective time to control field bindweed considering present cropping practices. High diluent volumes decreased control obtained from applica- tions of glyphosate to field bindweed and quackgrass [Agropyron repens (L.) Beauv.] in the field. Additional surfactant did not increase control of quackgrass at high diluent volumes. In the greenhouse, diluent volumes greater than 190 L/ha decreased glyphosate phytotoxicity on tall morningglory. Runoff from high diluent volumes became a factor Curtis Lloyd Sandberg when diluent volumes exceeded 190 L/ha. At 375 L/ha 50 to 75 percent of the spray solution ran off the leaf surface. Calcium was antago- nistic to glyphosate activity at high spray volumes or at calcium concentrations greater than 0.01 M at low volumes. 14C-glyphosate was translocated throughout the treated plants within 3 days; the greatest accumulation was in the meristimatic regions of roots and shoots in all species tested. In cross and longitudinal sections of stems and roots the 14C-glyphosate was localized in the phloem. Less than 25 percent of the applied herbicide was translocated from the treated leaf in all species. Studies indicated very little metabolism of glyphosate; aminomethylphosphonic acid was the major metabolite found, making up less than 15 percent of the total 14C. Of the applied 14C-glyphosate 50 percent disappeared from excised leaves within 25 days. Neither translocation studies nor thin layer chromatography of metabolites accounted for this loss. ACKNOWLEDGMENTS The author would like to express his sincere appreciation to his major professor, Dr. William F. Meggitt, for his guidance and support in this study and for making my experiences here at Michigan State University possible and rewarding. Gratitude is extended to Dr. Donald Penner for his laboratory guidance and assistance in the preparation of this dissertation. The assistance of Drs. R. J. Kunze, A. R. Putnam and M. J. Zabik as guidance committee members is gratefully acknowledged. The technical assistance of Robert Bond is especially appreciated. A very special thanks to my family, my wife, Jean, and girls, Jennifer, Melanie, and Tara for their love and understanding and for their many sacrifices to make this day possible. 11 TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . . . . CHAPTER 1: LITERATURE REVIEW . . . . . . . . . . Biology . . . . . . . . . . . . . . . . . . . . "Early" Control . . . . . . . . . . . . . . . . ' Cultural . . . . . . . . . . . . . . . . . . Early Chemicals . . . . . . . . . . . . . Control with Glyphosate . . . . . . . . . . . . Diluent Volume and Additives . . . . . . . . Soil Activity . . . . . . . . . . . . . . . Glyphosate Physiology . . . . . . . . . . . CHAPTER 2: FIELD BINDWEED CONTROL WITH GLYPHOSATE Introduction . . . . . . . . . . . . . . . . Materials and Methods . . . . . . . . . . . . . Results and Discussion . . . . . . . . . . . . Literature Cited . . . . . . . . . . . . . . . CHAPTER 3: EFFECT OF DILUENT VOLUME AND CALCIUM ON GLYPHOSATE PHYTOTOXICITY . . . . . . . Abstract 0 O O O O O O O O O O O O O O O O O O IntrOduction O O O O O O O O O O O I O O 0 iii Page vii 10 12 13 15 15 18 21 43 46 46 47 Page Materials and Methods . . . . . . . . . . . . . . . . . . . . 49 Results and Discussion . . . . . . . . . . . . . . . . . . . 51 Literature Cited . . . . . . . . . . . . . . . . . . . . . . 62 CHAPTER 4: ABSORPTION, TRANSLOCATION, AND METABOLISM OF 14c-cLYPHOSATE IN SEVERAL WEED SPECIES . . . . . . . 64 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 65 Materials and Methods . . . . . . . . . . . . . . . . . . . . 66 Results and Discussion . . . . . . . . . . . . . . . . . . . 69 Literature Cited . . . . . . . . . . . . . . . . . . . . . . 92 CHAPTER 5: SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . 94 LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . . . . I 97 APPENDICES O O O O O O O O O O O O O O O O O O O O 0 O O O O O O 105 iv LIST OF TABLES CHAPTER 2 1. The soil type, organic matter, treatment and rating dates for glyphosate studies initiated in 1974 and 1975 O O O O O O O O O O O C D O I C O O O O O O O O O I O O O 2. Control obtained from October postemergence applications of glyphosate to mature field bindweed initiated in 1974 . . . . 3. Control obtained from June postemergence applications of glyphosate to pre-bloom field bindweed initiated in 1975. . . 4. Control obtained from August postemergence applications of glyphosate to mature field bindweed initiated in 1975 . . . . 5. Control obtained from.July postemergence applications of glyphosate to hedge bindweed in full bloom initiated in 1975. 6. Fall postemergence applications of glyphosate for field bindweed control. . . . . . . . . . . . . . . . . . . . 7. Temperature laws for September, October, and November in Shiawassee and Saginaw Counties. . . . . . . . . . . . . . 8. Glyphoate phytotoxicity as affected by tillage two weeks after application of glyphosate on field bindweed . . . . . . 9. Postemergence applications of glyphosate in different tillage systems for field bindweed control. . . . . . . . . . 10. Postemergence applications of glyphosate for field bindweed control in a corn, soybean, navy bean, and Wheat rotation O O O O O O I O O O O O O O O O O O O O O O O 0 CHAPTER 3 1. The effect of diluent volume and additional surfactant on glyphosate phytotoxicity to quackgrass and field bindweed grown in the field . . . . . . . . . . . . . . . . . Page 19 22 23 24 26 29 3O 38 40 41 52 Page 2. Effects of diluent volume on glyphosate phytotoxicity at 1.68 kg/ha on tall morningglory 10 to 12 cm in height grown in the greenhouse . . . . . . . . . . . . . . . 53 3. The effects of calcium on glyphosate phytotoxicity to tall morningglory grown in the greenhouse. . . . . . . . . . 54 4. The interaction of calcium and diluent volume on tall morningglory height grown in the greenhouse. . . . . . . . . 56 5. The influence of calcium on the retention of sulfonine red dye on the leaf surfaces of tall morningglory grown in the greenhouse. . . . . . . . . . . . . . . . . . . . . . 57 6. The interaction of additional isopropylamine above that in the normal formulation and calcium an glyphosate activity to tall morning glory . . . . . . . . . . . . . . . 61 CHAPTER 4 l. 14C-glyphosate absorption and movement from the treated leaf 0 O O O O O O O O O O O I O O O O O I O O 0‘ O O I I O O 70 2. Translocation of 14C—glyphosate in 12 to 14 cm tall tall morningglory, 18 to 20 cm long field bindweed, 18 to 20 cm long hedge bindweed, 16 to 18 cm tall wild buckwheat, and 14 to 18 cm tall Canada thistle harvested and dissected into plant parts 3 and 14 days after treatment . . . . . . . 71 3. The effect of time and plant organs on the metabolism of C-glyphosate in 10 to 12 cm length field bindweed harvested 3, 7, and 30 days after treatment. . . . . . . . . 87 4. The effect of time and plant organs on the metabolism.of C-glyphosate in 10 to 12 cm.lenkh Canada thistle harvested 3, 7, and 30 days after treatment. . . . . . . . . 83 5. The effect of time and plant organs On the metabolism of C-glyphosate in 10 to 12 cm.length tall morningglory harvested 1, 7, and 21 days after treatment. . . . . . . . . 89 6. The loss of 14C—glyphosate from treated leaves of field bindweed and tall morningglory . . . . . . . . . . . . 91 vi LIST OF FIGURES Page CHAPTER 2 1. Proliferation of buds and reduction of growth in roots of (A) field bindweed and (B) hedge bindweed treated with sub—lethal rates of glyphosate. The control roots are on the left, and the treated roots are on the right. . . . . . . 28 Glyphosate was applied to field bindweed at 2.24 kg/ha in the fall. Profuse budding occurred at the crown as Observed in the photograph the following spring . . . . . . . 33 Proliferation of buds, deformity, and chlorosis of new leaves in (A) wild buckwheat and (B) field bindweed caused by sub—lethal rates of glyphosate. . . . . . . . . . . 35 Proliferation of buds, deformity, and chlorosis of new leaves in (A) hedge bindweed and (B) field.bindweed caused by sub—lethal rates of glyphosate. . . . . . . . . . . 37 CHAPTER 3 1. Glyphosate and sulfonine red dye retention on tall morningr glory leaves when applied at 130 and 750 L/ha and photo- graphed while wet and dry. (A) 130 L/ha wet, (B) 130 L/ha dry, (C) 750 L/ha.wet, (D) 750 L/ha dry . . . . . . . . . . . 59 CHAPTER 4 1. Translocation of 14C-glyphosate in field bindweed 18 to 20 cm in length. The treated plant (A) and corresponding radioautograph (B) of field bindweed harvested 3 days after treatment. The treated plant (C) and corresponding radioautvograph (D) of field bindweed harvested 14 days after treatment. The treated leaf is marked with an arrow. . . . . 74 vii Translocation of l4C—glyphosate in hedge bindweed 18 to 20 cm in length. The treated plant (A) and corresponding radioautograph (B) of hedge bindweed harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (D) of hedge bindweed harvested 14 days after treatment. The treated leaf is marked with an arrow. Translocation of 14C-glyphosate in Canada thistle 14 to 18 cm tall. The treated plant (A) and corresponding radioautograph (B) of Canada thistle harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (D) of Canada thistle harvested 14 days after treatment. The treated leaf is marked with an arrow. Translocation of 14C—glyphosate in tall morningglory 12 to 14 cm tall. The treated plant (A) and corresponding radioautograph (B) of tall morningglory harvested 3 days after treatement. The treated plant (C) and corresponding radioautograph (D) of tall morningglory harvested 14 days after treatment. The treated leaf is marked with an arrow . . . . . . . . . . . . . . . . . . Translocation of 14C—glyphosate in wild buckwheat 16 to 18 cm tall. The treated plant (A) and corresponding radioautograph (B) of wild buckwheat harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (D) of wild buckwheat 14 days after treatment. The treated leaf is marked with an arrow . . . . . . . . . . . . . . . ... . . . . . . Location of 14C-glyphosate in field bindweed stems harvested 3 days after treatment. Treated plant (A) and corresponding radioautograph (B) of a stem longitudinal section. Treated plant (C) and corresponding radioautograph (D) of a stem cross section. . . . . . . . Location Of 14C-glyphosate in field bindweed roots harvested 3 days after treatment. Treated plant (A) and corresponding radioautograph -(B) of. a root longitudinal section. Treated plant (C) and corresponding radioautograph (D) of a stem cross section. viii Page 76 78 80 82 84 86 INTRODUCTION Excellent selective herbicides are available for annual weed control, which alone or in combination, control most annual weeds in many crops. However, field bindweed (Convolvulus arvensis L.) and other perennial weeds often escape control with these herbicides. Because these herbicides provide excellent annual weed control, the number of cultivations are reduced, often eliminated. This practice, along with less competition from annual weeds is allowing field bind- weed and other perennial weeds to become established. The infestation of field bindweed in Michigan is increasing rapidly, especially in the thumb and on muck soils. Field bindweed competes with crops resulting in lower yields and increased costs. Soil sterilants have provided some control of field bindweed, however, they render the soil sterile for l or more years. Field bind— weed control with 2,4-D and other phenoxy herbicides have been the major means of chemical control in cropping situations. Translocation of 2,4-D is for the most part to meristimatic regions of shoots, therefore, it does not kill the root systems and continual retreatment, often two or three times a season, is required. The use of 2,4-D is limited to crops which are resistant to 2,4-D. Glyphosate [Nf(phosphonomethyl)glycine], a non-selective herbi- cide introduced in 1971.(8) has activity on field bindweed when foliar applied. Glyphosate has no residual activity in most soils, there— fore, it can be applied prior to or following a crop with no injury to the crop or future crops. It is essential, however, that the control be at least one season and that glyphosate application be adapted to current cropping systems. The objectives of this study were to (l) evaluate the activity of glyphosate on field bindweed and to establish herbicide and management practices which provide effective control of field bindweed, (2) to evaluate the effects of diluent volume and cal- cium concentrations on glyphosate phytotoxicity, (3) to study absorp— tion, translocation, and metabolism of glyphosate. CHAPTER 1 LITERATURE REVIEW Biology Field bindweed (Convolvulus arvensis L.) a troublesome perennial weed of European origin (9, 43, 94), was first reported in Virginia in 1739 and then in Topeka, Kansas in 1877. Field bindweed has also been called wild morningglory, European bindweed,creeping jenny, creeping charlie, Russian creeper (23, 24, 27, 80, 101) and possession vine (5). Field bindweed is disseminated by seed, root fragments of almost any size carried by farm equipment, root extensions at the parameters of the infestation, and roots which may be transferred with soil (38, 43, 81). Field bindweed roots have been found as deep as 7 m (9, 27, 28, 94) with the greatest mass of root growth within 0.6 m of the soil surface (15, 27) and to expand the parameter of the infestation by 3 m per year (9, 14, 27, 94). Lateral roots develop from numerous ad- ventitious buds on the root (42). Rhizomes, which are produced from lateral roots, penetrate the soil surface forming new crowns (42, 94). Conditions favorable to growth stimulate bud initiation. buds may be produced by the dozens or even hundreds. This activity occurs espe- cially during warm weather and after destruction of top growth by cultivation. Vegetative reproduction is favored by bud production and large food reserves. After old roots have been severed many times they may send up numerous rhizomes from the severed ends. No fluctuation in carbohydrate reserves occurred in roots in the top 30 cm of soil during the growing season (11). Reserves decreased slightly from May to September in roots 30 to 60 cm deep, and a large decrease in root reserves occurred during the growing season in roots below 60 cm. A greater decrease in root reserves occurred following cultivation. Field bindweed has flowers about 2 to 2.5 cm in diameter, white to pink in color (95), which are open only in the morning (81). The plant starts blooming in mid-June. Warm, dry, sunny weather favors seed production whereas cloudy weather inhibited flower and seed pro— duction (18, 28, 43, 94. 95). Consequently seed set is very low and usually totally fails in Michigan. As many as 1/4 million seeds/ha were found in one crop and one million seeds/ha were found along road— sides (95). Bindweed seed fed to animals often pass through the digestive tract unharmed. The mature seed has a shape similar to closely related genera, it is hard, brown or black in color (80). The seed is born in a two celled capsule which usually contains four seeds shaped like a pear (10, 18). When only one seed develops it is more spherical. The seed is about 0.1 cm in length. Immature seeds can germinate immediately, however, mature seeds may be dormant for 30 to 50 years (18, 95). Twenty-eight days were sufficient for seeds to develop impermeability after flowering (18). Seeds germinate from 0.5 to 40 C with an optimum temperature of 20 to 30 C. Germination occurs from April to September. Bindweed seedlings have heart shaped cotyledonary leaves. The seedling develops a deep tap root in about 11 weeks and may have lateral spread of 3 m the first year (27, 95). The leaves of field bindweed have many different shapes and sizes (95), which are associated with the amount of moisture available (42). Field bindweed is often confused with hedge bindweed (Convolvulus sepium L.), tall morningglory [Ipomoea purpurea (L.) Roth.], and wild buckwheat (Poly- gonum convolvulus L.) (43). Field bindweed causes loss in many crops not only due to compe- tition for light, nutrients, and moisture but also by serving as a host for disease, insects, and other pests (45). It hinders harvesting of many crops by becoming tangled in cutter bars, threshing drums and other moving parts of harvest equipment. It may add moisture content to the grain (55). It prevents penetration of pesticides and increases the number of culls and non—harvestable fruits (38, 45). It increases labor costs and reduces land and loan values (43). Field bindweed has been reported to cause grape losses up to 75 percent (51). Other researchers have reported up to 89 percent yield reduction due to field bindweed (29, 86). Harvey reported $374 million per year loss to weeds in California of which field bindweed was one of the six worst weeds in the state (35). In dense crop stands bindweed will twine to the top of the canopy to get light (9). Field bindweed has been proclaimed a noxious weed in many states (15, 35, 38, 54). Even though field bindweed was originally introduced on the east coast of the United States, it developed most rapidly in the mid- west and western states (9) with some states, washington, California, North and South Dakota having over 400,000 hectares of field bindweed. Due to dry conditions, even if roots and rhizomes were killed the seed would reinfest the land. Field bindweed has wide distribution in the North Central region, however, it has only been the last few years that field bindweed has become a major weed problem. This is due to the greater use of herbicides for annual weed control which are in- effective in perennial weed control (45). Due to better annual weed control chemicals, less cultivation is applied and cultivation has been a major control method for field bindweed. "Early" Control Cultural Many control methods have been used for field bindweed starting as early as 1908 (9). The conclusion in 1908 was to starve the roots to death by keeping the plant from developing green leaves (20, 81), however, it was observed in 1911 that it had to be cut 30 times to do this at the cost of $3.60 per hectare (15). Salting was used at 22,700 kg per ha with a second application weeks later (18, 43). Salt was expensive and made the soil sterile for crop production. Mulches of manure and straw, piled deep enough to stop all light and air ex— change, and tar paper were applied in Utah to smother bindweed and starve the plant to death (81). Hogs, sheep, and goats were used to weaken or kill perennial weeds (81). Rotations of crops such as wheat (22, 24), corn,potatoes, alfalfa (102), and soybeans (83) were used to compete with field bindweed. Researchers (81) even tried digging out the roots which was a hopeless task in areas or large infestations. Cultivation was the major control method, Cox (20) used a V-shaped cutter, some used homemade weed cutters (81). Seely, et a1. (74) used plows, duck foot field cultivators, rotary rod weeders, and rod weeders with sweeps. There was no advantage to cultivation deeper than 10 to 15 cm and cultivation was required every 12 days from spring to September 15 (61, 73, 85, 86). Cultivation decreased root reserves more completely than applications of sodium chlorate. Cultivating at emergence did not reduce carbohydrates more than less frequent culti- vation (12, 86). Early Chemicals Chemical control began in the United States in 1911 (102) with the first chemical to show activity on bindweed being sodium chlorate in 1927 (59, 91). Sodium chlorate was expensive, hazardous, and sterilized the soil for several years. It required 450 to 540 kg/ha (43). K. M. G. (kill morningglory) is an acid solution of arsenic which killed bindweed roots a meter or more deep (43). Other soil sterilants such as monuron [(3-pfchlorophenyl)-l,1-dimethylurea], fenuron (l,l-dimethyl-3-phenylurea), TBA (trichlorobenzoic acid), PBA (Polychlorobenzoic acid), and picloram (4-amino-3,5,6-trichloro- picolinic acid) became available in the 19508 and 19608 (24, 49, 84) for non-cropland. Non-selective herbicides, such as dicamba (3,6— dichlorofgfanisic acid), picloram, 2,3,6-TBA (2,3,6-trichlorobenzoic acid), and fenac [(2,3,6-trichlorophenyl)acetic acid] were applied at relatively low rates after small grains to reduce the stand of field bindweed (24, 31, 40). TBA and PBA leave the soil sterile and are expensive, therefore, they are only used in small areas (58). They prevent economical growth of wheat for l or 2 years. At a given rate 2,3,6-TBA was more effective than TBA or than PBA (58). Experimenta- tion with 2,4-D K2,4-dichlorophenoxy)acetic acidfl began in 1945 (59, 67) and field bindweed control with this and other phenoxy herbicides have been the major means of chemical control since that time. Field bindweed stands were reduced 90 percent or more with three applications over 7 years (24). A single application of dicamba or picloram at rates of 0.6 and 0.2 kg/ha, respectively, resulted in 90 percent or more reduction in stand. Similar control was obtained with 2,4-D (23). Translocation of 2,4-D and picloram is mostly to the young leaves and meristimatic regions of the stem (3). Translocation of 2,4-D and picloram was greatest during the seedling stage of growth of field bindweed (2). Some strains of field bindweed have been claimed to be more susceptible to 2,4—D than other strains (35, 89, 90). Whitworth (89) found a range from 87 percent reduction in weight to 83 percent increase in weight one month after treatment with 2-4-D. More effective control of field bindweed occurred with 2,4-D than 2,4,5-T or MCPA (24). Several retreatments per year were required. Phillips (59) suggested that of the phenoxy's, silvex suppressed bindweed growth for the longest period, then 2,4-T and 2,4-D, however, none of these gave satisfactory control. The effectiveness of silvex is related to longer residual in the soil than the other phenoxy's (98). Effective control with 2,44D was provided when applied to vigorously growing field bind- weed at the bud stage. Wiese (99) reported that 2,4-D was the most effective phenoxy. Bindweed control was most effective when the chemical program included competitive crops, post harvest cultivation, and herbicide treatment (23, 59,.70, 97). Trifluralin (a, a, aftrifluoro-Z,6-dinitro—N,Nfdipropylfpf toluidine), dichlobenil (2,6-dichlorobenzonitrile) and other compounds were found to give greater field bindweed control when applied as sub-surface layer, 15 to 30 cm deep (1, 32, 49, 66, 88). Due to exten- sive injury caused by dichlobenil (32, 41), Trifluralin is used in controlling field bindweed in orchards and vineyards (49). Shoots from rhizomes below the "tarp-like" layer became swollen, twisted, and unable to penetrate the layer (48). Injury occurred to corn and wheat, which are trifluralin sensitive crops, when grown on top of the layer. No injury was seen on crops with resistance to trifluralin. Control with Glyphosate Glyphosate is a broad spectrum herbicide introduced in 1971 (8). Because of phloem translocation to the meristematic regions of Shoots and roots it provides excellent perennial weed control (78). The mode of action of glyphosate as proposed by Jaworski (39) is the inhi- bition of the biosynthesis of the aromatic amino acids. It is a foliar applied herbicide which appears to have very limited soil activity (79). Season long control of field bindweed can be obtained from one application of glyphosate (25, 53, 56, 63, 93). However, control of field bindweed has been variable (21), resulting in a large reduction of stand one time and almost no control the next. In all cases a ‘ second or third application provided better control than a single application (25). Davison and Bailey (21) reported less regrowth with 2,4-D, MCPA (2~methyl-4-chlorophenoxy-acetic acid) and MCPB [4-(2-methy1-4- chlorophenoxy) butyric acid] at 2 kg/ha than glyphosate at the same rate. Ogg (56) reported that field bindweed recovered rapidly, usually within 1 year after treatment. He also found 2,4-D to be more effec- tive than glyphosate. Others have suggested at least 2 years of control with glyphosate (71). Best results were achieved when glyphosate was applied to vigorously growing field bindweed (25) in or after the flower bud 10 stage (76). When glyphosate was applied prior to bud stage, prolific regrowth occurred. Rainfall within 8 hours after treatment reduced glyphosate activity (6, 63). Heavy regrowth required a greater amount of herbicide than light infestations. Glyphosate is a non-selective herbicide, therefore, treatment of weeds within a crop require special types of application. Using a recirculating sprayer, tall weeds, at least 61 cm taller than the crop, can be controlled in crops which are sensitive to glyphosate (52). This method, however, provided no control for low growing weeds like field bindweed, Post-emergence directed applications have been used in soybeans [Glycine max (L.) Merr.] with a small amount of injury occurring to the soybeans as long as the spray solution did not go above 10 cm on the soybean stem. Others have experimented with shielded sprayers in cotton (Gossypium hirsatum) for field bindweed control (25). Applying glyphosate to 75 to 80 cm between 105 cm rows of cotton effectively controlled field bindweed which was entwined with the cotton plants without injury to the cotton. Tillage prior to and after glyphosate application is important in fitting this chemical into agronomic systems. Fisher et a1. (25), concluded that field bindweed control in a fallowed field was best if tilled in April and then treated in June when the bindweed was vigorously growing. Field bindweed in cultivated fields was more effectively controlled than field bindweed on fallowed fields. Diluent VOlume and Additives There has been interest in combining glyphosate in tank mixes and split applications with other chemicals such as atrazine 11 [2-chloro-4-(ethylamino)-6-(isopropylamine)fgftriazine], propachlor (2-chlorojgfisopropylacetanilide), terbacil (3ftgrtfbutyl-5-chloro- 6~methyluracil), simazine (2—chloro—4,6-bis(ethylamino)j§ftriazine), amitrol (3-aminofigftriazole), and other wettable powders, especially for no-till applications (60, 75). When combined with certain wettable powders, glyphosate was no longer active (34). Phillips (60) reported that atrazine, propachlor, and non-herbicidial wettable powders decreased glyphosate phytotoxicity on sorghum (Sorghum vulgare Pers.). Selleck (75) found amitrol and simazine reduced activity of glyphosate on smooth bromegrass (Bromus inermis L.) when sprayed as a tank mix; however, there was no antagonism when sprayed separately the same day or later. He also showed that bromacil (5-bromo-3-sec-butyl-6- methyluracil), diuron [3-(3,4-dichlorophenyl)-l,l-dimethylurea], and amitrol reduced glyphosate toxicity to common mildweed (Asclepias syriaca L.) and bouncing bet (Saponaria officinalis L.). Amitrol did not reduce control to toadflax (Linaria vulgaris Hill.) when tank mixed with glyphosate as did all other herbicides tested. No antagonism was seen in combination with any of the herbicides on bluegrass (Egg pratensis L.), goldenrod (Solidago spp. L.) or brambles (Rubgg’spp. L.). Combinations of glyphosate with liquid nitrogen gave enhanced kill of winter rye [Secale cereale (L.) var. Balboa] (57). Nitrogen fertili— zers only enhanced the initial injury with complete recovery in 6 weeks on perennial sod species. Peters et a1. (57) also reported that complete fertilizers reduced glyphosate activity. Calcium, iron, zinc, and aluminum have been reported to reduce glyphosate phytotoxicity (34, 60, 72, 100), whereas Wills (100) reported potassium, sodium, ammonium, and calcium to increase glyphosate 12 activity in descending order on purple nutsedge (Cyperus rotundus L.). Ammonium sulfate appeared to activate glyphosate either in a tank mix or when applied separately (16, 84, 87). Cations tended to reduce glyphosate activity, whereas anions had little or no effect on activity (60, 100). High diluent volumes also reduced glyphosate activity both in the field and in the greenhouse (60, 65, 72, 101). Increasing the additional surfactant concentration above that in the formulation produced variable results; however, the negative effect of high diluent volume was partially overcome (65, 72, 101). Soil Activity Glyphosate is inactivated when it comes in contact with the soil (33, 47, 64, 79) which allows for crOps to be planted after glyphosate application with no injury to the crop. The initial inactivation was provided by rapid bonding of glyphosate to clay and organic matter (33, 64, 67, 77, 79). It appears to be absorbed by the soil similarly to orthophosphate fertilizer (61). There is a correlation between glyphosate adsorption to unoccupied phosphate sorption capacity. Adding other phosphate sources to the soil in addition to glyphosate decreased glyphosate binding (79). Kaolanite did not adsorb or inactivate glyphosate to the same extent as montmorillonite or organic matter (64). Glyphosate has very little mobility in the soil (67, 77). Microbial degradation of glyphosate to C0 is the secondary 2 inactivation process in the soil (67, 79). No chemical degradation appears to be involved in the inactivation process (79). In 28 days up to 50 percent of the applied 14C-glyphosate had been converted to 13 C0 (67, 79). The decomposition rate was decreased when the pH was reduced. Rueppel et a1. (69) reported 90 percent conversion to C02 of both glyphosate and its major metabolite, aminomethylphosphonic acid (AMP), within 12 weeks. Glyphosate is stable in sunlight, not leached in the soil, and has only a minimal effect on the microbial population of the soil environment (69). Glyphosate Physiology The activity of a foliar applied herbicide depends not only on the activity of the compound following absorption into the plant, but also upon how much is absorbed and translocated in the plant. The type of translocation (acropetal or basipetal) is also important in perennial weed control. Basipetal movement is essential to move foliar applied herbicides into the roots and rhizomes. Sprankle et a1. (78) reported 30 to 50 percent absorption of applied 14C-glyphosate into quackgrass leaves after 3 days. Wyril and Burnside (91) reported 25 to 67 percent absorption depending on the species. Glyphosate is translocated both acropetally and basipetally (8, l3, 19, 63, 77, 82, 103) with the greatest concentration of glyphosate accumulating in the meristimatic regions of the shoot and roots. Translocation is rapid, however, tillage of treated quackgrass [Agrgpyron repens (L.) Beauv.] after 1 day allowed for more buds to survive than tillage after longer intervals (13, 19, 77). Buds developing after sub-lethal doses of glyphosate are chlorotic and deformed along with any subsequent regrowth (72). No effects of glyphosate appeared on foliage present at time of treatment unless the application rate was sufficient to cause death of the foliage. 14 The contribution of glyphosate metabolism to the variability in perennial weed control is not known, however, very little metabolism of glyphosate has been found in plants (63, 69, 103) AMP was the major metabolite isolated from plants (63, 68, 69). CHAPTER 2 FIELD BINDWEED CONTROL WITH GLYPHOSATE Introduction Field bindweed (Convolvulus arvensis L.) is a troublesome perennial weed of European origin (20, 38). It is also known as wild morningglory, European bindweed, creeping jenny, creeping charlie, and Russian creeper (3, 5, 10, ll, 13, 32). Field bindweed can be spread by means of seed, root fragments carried by farm equipment, root extensions at the parameters of the infestation, and roots which may be transferred with soil (20, 21). Field bindweed roots have been found as deep as 7 m (3, 38) and to expand the parameter of the infestation by 3 m per year (3, 5, 13, 38). From lateral roots, rhizomes are produced which penetrate the soil surface forming new crowns (19, 38). warm dry weather favors seed production (38), as many as 1/4 million seeds/ha were found in one crop and one million seeds/ha were found along roadsides (95). Seeds have been known to remain dormant for 30 years. Field bindweed causes loss in many crops due to competition for light, nutrients, and moisture, and is a host for disease, insects, and other pests (22). It hinders harvesting by becoming tangled in cutter bars, threshing drums and other moving parts of harvest equip- ment, and adds moisture content to the grain (28), prevents penetra— tion of pesticides, and increases the number of culls and 15 16 non-harvestable fruits (17, 22). Field bindweed has been reported to cause grape losses up to 75 percent (26). Harvey reported $374 million per year loss to weeds in California and field bindweed is one of the six worst weeds in the state (15). Field bindweed has been proclaimed a noxious weed in many states (6, l5, 17, 27). It has been a major problem in the midwest and western United States for many years (33) and has increased as a major weed problem in Michigan over the last few years. This increase is due to a greater use of herbicides for annual weed control which are ineffective in perennial weed control (22). Beginning as early as 1908 attempts have been made to control field bindweed (8). The conclusion at that time was to starve the roots to death by keeping the plant from developing green leaves (8, 33). Thirty weed cuttings were necessary at the cost of $3.60 per hectare (6) to control field bindweed by this method in 1911. Salting was also used at 22,700 kg/ha with a second application weeks later (7). However, salt was expensive and made the soil sterile for crop production. Mulches of manure and straw, piled deep enough to stop all light and air exchange, and tar paper were applied in Utah to smother and starve the plant to death (33). Hogs, sheep, and goats were used to weaken or kill perennial weeds (33). Rotations of crops such as wheat (39), corn, potatoes, alfalfa (40), and soybeans (34) were used to compete with field bindweed. 'Researchers (33) even tried digging out the roots which was a hopeless task in areas of large infestations. Cultivation was the major control method used, Cox (8) used a V-shaped cutter, while others used homemade weed cutters (33). Seeley et al. (31) used plows, duck foot field cultivators, rotary rod l7 weeders, and rod weeders with sweeps. There was no advantage to culti- vation deeper than 10 to 15 cm and cultivation was required every 12 days (29). Chemical weed control began in 1911 (40) with the first chemical to show activity on bindweed being sodium chlorate in 1927 (36). Sodium chlorate was expensive, hazardous and sterilized the soil for several years. Other soil sterilants such as monuron [3-(p-chlorophenyl)-l, l-dimethylurea], fenuron (1,l-dimethyl-3-phenylurea), PBA (polychloro- benzoic acid), and picloram (4-amino-3,5,6-trichloropicolinic acid) (1), became available in the 19508 and 19608 (12) for use on non-crop- land. Non-selective herbicides such as dicamba (3,6—dichlorofgfanisic acid), picloram and 2,3,6-TBA (2,3,6-trichlorobenzoic acid) were applied at relatively low rates after small grains to reduce the bind- weed stand (11, 18). Experimentation with 2,4-D [(2,4-dichorophenoxy) acetic acid] began in 1945 (29) and is still a major chemical used today. Trifluralin, (§,a,§ftrif1uoro-2,6-dinitro-N,Nfdipropylfpf toluidine), and other compounds were sub-surface layered for field bindweed control beginning in the early 19708 (16, 24, 30, 35). Control was limited to crOps which were tolerant to trifluralin. The layer could not be broken or the rhizomes of the field bindweed would penetrate the surface and again become established. Glyphosate [Nf(phosphonomethyl)glycine] is a broad spectrum herbicide introduced in 1971 (2) which has activity on bindweed (9, 12, 23, 25); however, results have often been inconsistant. Studies were designed to determine the herbicidal efficacy of glyphosate on field bindweed on mineral and muck soil and to determine if eradication, 18 as mentioned by many early bindweed researchers, (6, 20, 21, 33) could be obtained and to evaluate glyphosate phytotoxicity at different stages of growth. Materials and Methods Field studies were conducted in 1974 through 1977 at several locations in Michigan. Plots were 3.1 by 6.1, 3.1 by 12.2, or 3.1 by 15.2 m, all treatments were replicated three times. Glyphosate was applied with a tractor mounted sprayer at 2.11 kg/cmz pressure and 215 L/ha. The formulation of glyphosate used contained 0.89 kg/L of gly— phosate as the isopropylamine salt and 0.45 kg/L of surfactant. Field bindweed control was visually rated on a 0 to 10 scale; 0 equaled no control and 10 equaled 100 percent control. Field experiments were conducted at three locations on field bindweed and one location on hedge bindweed to determine the effect of rate of application, time of application, length of control, and the benefit of reapplication of glyphosate for bindweed control. The study was a split-split plot in design with three plots in each replication being treated at each glyphosate rate the first year, two plots received reapplication the second year, and one the third year. Field bindweed was treated at three locations with studies initiated in October, 1974 at the first location, June, 1975 at the second location, and Augu8t, 1975 at the third location. Hedge bindweed was treated at a fourth location in July, 1975 (Table 1). Terbacil (3f£g££fbutyl-5-chloro-6-methy1uracil) was applied at 0.86 kg/ha for annual weed control. l9 unma .mN nooaoumom . snaH .8H have namH .mH umamsa cams .H omnamuamm mama .sH sass mnma .mN sooaouoom muoa .oH hash ¢.m Smoa mmao modem e unaa .ma umpEOuoom hams .mu unswsa hams .ma umswsa puma .c umaws< omaa .mm umows< man .mH umpfioueom mmma .nH umowa< o.wm 3052 m unma .mH sash mesa .sH sax asma .oN an: cams .wH ems sass .H mass mess .HH sass mama .NH mass m.m amoa swag asamm N mnma .NH umows< unofl .m mosh omma .mH nooouoo puma .m Honouoo mnaa .mm Honouoo mnma .na uooamueom «sea .m wooouoo m.m Emoa zmao eufluono H mm m mm o no m 808 mow Auooouoov ooh o no moo u e flu m u e u u H spoons oacmmuo u as m an A mmma pom «Boa 8H wooaumooa snow on woumwuwofi moseoum mummooezammo mouse wagon» woo uooaumouu .uouume owomwuo .ooxu HHom one .H oaomH 20 To determine the latest date at which glyphosate could be applied to field bindweed in the fall and achieve desired control, glyphosate applications of 2.24 and 3.36 kg/ha were made to mature field bindweed September 25, and 28, October 8, and 14, and November 5, 1976. The field bindweed was on muck soil with 48 percent organic matter at one location and sandy clay loam with 5.5 percent organic matter at the second location. Each location received tillage in July 1976. Ratings were taken June 3, and August 17, 1977. Terbacil at 1.12 kg/ha was applied for annual weed control. To evaluate the effect of tillage on glyphosate phytotoxicity, glyphosate was applied June 7, 1975 to pre-blossom field bindweed on a sandy clay loam of 3.9 percent organic matter at 1.12, 1.68, 2.24, and 4.48 kg/ha. On June 21, 1975 half of each plot was plowed 25 cm deep with a moldboard plow. Plots ‘were rated July 11, 1975, May 18, 1976, September 1, 1976, and July 15, 1977. Terbacil at 1.12 kg/ha was applied to control annual weeds. At two other locations, one a muck soil of 48 percent organic matter and the other a sandy clay loam of 5.5 percent organic matter, glyphosate was applied at 2.24 kg/ha to mature field bindweed on September 25, 1976, June 3, 1977, and July 20, 1977. Each location received tillage in July, 1976, preceding the study. Tillage was performed with a moldboard plow on the sandy clay loam and a disc on the muck soil. Tillage occurred on November 6, 1976, May 5, 1977, and June 10, 1977. Ratings were taken August 17, 1977. Terbacil was applied at 1.12 kg/ha for annual weed control. A rotation study was initiated in 1975 including corn, soybeans, navy beans, and wheat to determine when glyphosate could be most 21 effectively applied. Glyphosate was applied August 15, 1975, June 15, 1976, October 14, 1976, and May 19, 1977 to field bindweed on a muck soil with 33.7 percent organic matter at 1.12 and 2.24 kg/ha. No cultivation had occurred for 3 months prior to August 1975 treatments, plots were cultivated 2 weeks prior to June 1976 treatments. No cultiva- tion preceded October 1976 and May 1977 treatments. Michigan 369 corn, Sanilac navy beans, and Harasoy soybeans were planted June 14, 1976 and May 23, 1977. Tecumpseh wheat was planted October 20, 1976. Seven different rotations were included (table 9). Ratings were taken May 19, 1977 and August 23, 1977. Results and Discussion Excellent control of field bindweed was achieved with glyphosate for 1 year after application for all treatment rates above 0.56 kg/ha at each application date (Tables 2, 3, and 4). Satisfactory control of field bindweed did not continue after a single application of gly- phosate through the third season after treatment, with a decrease in control observed during the second growing season. A second applica- tion of glyphosate made during the second season, in most cases, gave better control of field bindweed early in the third year than a single application. However, the control from two applications were no better than one application by the end of the third season, except for the August treatment. Increased control in August treatments with. a second application was observed at rates higher than 0.84 kg/ha, however, when third season August treatments are compared to ratings of June and October treatments rated at a similar time period after application the control was similar. Three applications provided 22 NOOH u ca .Houuooo on u o mamom OH on o m no man mwowumu Hmomfi> m.amuo:a an Ho>OH Nn can on unoumwmwv manomofimaowwm uoo mum muouuoa doaaoo nufis mama: .Houuooo .umou swoop oameuada A .onma .MH Hmoouoo vow .nnma .mm nooouoo muoam eOHMHoomm on come mooHumOHHmamou one «Baa .m Honouoo moms mum: macauooaaqnm ooaoaouomm «no m.w HP m.a ans m.s sum N.» em.m on a me a sass sun s.m Ale m.m a.“ m.a are a.w om.m me A «has an o.m aim o.s mus ~.h A-m m.» em.m «has hum o.o H o.oH Hus m.a Hum m.» we.H on a we a seed «no 8.0 sue n.m Hus w.a sue ~.a mo.H mm a «has cum m.m m m.~ Cue o.s an: N.m mo.a seas mic «.5 as m.m ans m.m Hum o.m sm.o on a me a «has u-m ~.s a-e m.s Hus m.s “no m.m sm.o me a «Asa a o.N one m.s Cue o.h a-» o.m sm.o «has mummoeasau a~\sa\m aa\m\e 85\w\oa ma\sa\s Ame\wxv mug mfiwumwuu mummw UGOBUMOHH wowumu Houuooo mom: 9 «Rafi 8H woumauaow wooseofio VHOHH assume ou ouomonehaw mo maoaumoaaoom oosowuoaoumoo Honouoo Scum vooamuno Houuoou .N magma 23 .Houuooo NOOH u ca .Houuoou on n o .onom oa ou o o no 888 mwowumu Hmoma> .umou omomn manauaaa 8.888899 mo H8>OH Nm woo um uoouommao manomoamaowfim uoo mum muoquH doaaoo sows mamQZA .8888 .88 88x 888 .8888 .8 8888 muoam voHMHooem ca 8888 maoaumOHHmmmou mom mmma .8 Oman oofiammm mms oofiownuon mayo 88 8.8 8-8 8.8 8-8 8.8 88 8.8 88.8 88 8 88 8 8888 8:8 8.8 8-8 8.8 8-8 8.8 8 8.88 88.8 88 8 8888 8 8.8 8.8 8.8 8.8 8.8 88 8.8 88.8 8888 8-8 8.8 8.8 8.8 8 8.88 8 8.88 88.8 88 8 88 8 8888 8.8 8.8. 8.8 8.8 8.8 8.8 8 8.88 88.8 88 8 8888 8-8 8.8 88 8.8 8-8 8.8 8 8.88 88.8 8888 8-8 8.8 8-8 8.8 . 88 8.8 8-8 8.8 88.8 88 8 88 8 8888 8-8 8.8 8-8 8.8 8-8 8.8 8 8.88 88.8 88 8 8888 8-8 8.8 8-8 8.8 8-8 8.8 88 8.8 88.8 8888 8-8 8.8 8-8 8.8 8-8 8.8 88 8.8 88.8 88 8 88 8 8888 88 8.8 8.8 8.8 8-8 8.8 88 8.8 88.8 88 8 8888 88 8.8 8-8 8.8 88 8.8 8-8 8.8 88.8 8888 8888888888 8888888 8888888 8888888 8888888 . 8888888 8888888 88888 888888888 omoaumu Houosoo woo: mumm m . 8888 88 888888888 88838888 88888 Eooaooue cu mummonehaw mo mGOHumOHHmom oooowuoaoumom meow Eoum eoawMuno Houuooo .m canoe 24 Nooa u OH .Houuooo o: o .onum OH on o 8 so 888 mmcwumu Hmsmfi> .Houuooo .umou ownmn oaeauaze 8.888839 88 Ho>oH Mm 858 um ooouowmwo eauomofiw88mam uoo mum muoouoa 808808 3883 memo: muoaa eOHMHUon Cu meme o .8888 .mH umsws< woo .88mH .mN unsw=< 88088888888888 new m8ma .mH umsws< 8888888 883 ouaoaouon ween 8 8.88 88 8.8 8-8 8.8 88 8.8 88.8 88 8 88 8888 8-8 8.8 8-8 8.8 8-8 8.8 88 8.8 88.8 88 8888 8 8.8 8 8.8 8:8 8.8 8 8.88 88.8 8888 8-8 8.8 8-8 8.8 8-8 8.8 88 8.8 88.8 88 8 88 8888 8-8 8.8 8-8 8.8 8-8 8.8 8 8.88 88.8 88 8888 8 8.8 8 8.8 818 8.8 8 8.88 88.8 8888 8 8.88 8-8 8.8 8.8 8.8 8-8 8.8 88.8 88 8 88 8888 8-8 8.8 8-8 8.8 8+8 8.8 8-8 8.8 88.8 88 8888 8 8.8 8 8.8 888 8.8 8-8 8.8 88.8 8888 88 8.8 88 8.8 888 8.8 888 8.8 88.8 88 8 88 8888 88 8.8 88 8.8 88 8.8 888 8.8 88.8 88 8888 8 8.8 8 8.8 88 8.8 88 8.8 88.8 8888 8888888888 8888888 8888888 888888 8888888 8888888 meoumouu mummy woumoua wafiumu 8088800 @883 o m8m8 88 888888888 88838889 oaoqm 882886 cu 8888858888 mo 880888888888 oooomhoEmumoo umsms< Eoum eocamuoo 8088800 .8 88888 25 excellent control throughout the duration of the experiment. It appears that glyphosate completely kills the above ground portion of the plant, but not the root system. It inhibits the production of buds for about two seasons, after which buds are produced and field bind- weed begins to regrow. In the greenhouse 6 to 9 months were required to obtain new top growth after all top growth had been killed. Hedge,' bindweed, however, was completely controlled for 3 years with one application of glyphosate at 1.12 kg/ha (Table 5). Therefore, no additional control was obtained with retreatment. Hedge bindweed roots are more shallow and less extensive when compared to field bindweed. Hedge bindweed roots in the greenhouse were injured more than were field bindweed roots from equal rates of glyphosate (Figure 1). It is observed that when the roots are not completely killed a proliferation of buds occur on the rhizomes and the roots. These buds will grow and develop new rhizomes and new crowns, therefore, a sublethal rate of glyphosate may, in the end proliferate field bindweed instead of control it. Glyphosate provided excellent control of field bindweed on muck and mineral soils when applied as late as October 14, 1976 and rated June, 1977 (Table 6). No control was obtained from November treat- ments, eventhough, the field bindweed was green and no apparent freeze injury had occurred at the time of treatment. Reduced control was because of freezing temperatures every night after treatment (Table 7). After treatment the bindweed on mineral soil turned black and appeared dead prior to freezing in the fall. After application of glyphosate on muck soil the field bindweed turned yellow and then regained a green color and the foliage was not killed until frozen by November 26 NOO8 u O8 888 8088808 08 u 0 .88888 O8 08 o 8 8o 888 8888888 88888> .8088808 .8888 88888 88888888 8.888889 88 88>88 Nm 888 88 88888mw88 8888888888w88 808 888 8888888 805808 8883 88882 n .8888 .88 888888 888 8888 .88 8888 8uo88 888888888 08 8888 88088888888888 v88 mmm8 .88 8888 8888 8883 880888888888 8888888888 8 8.88 8 8.8 8 8.8 88 8.8 88.8 88 8 88 8 8888 8 8.8 8 8.8 8 8.8 8 8.88 88.8 88 8 8888 8 8.88 8 8.88 8 8.88 8.8.8 88.8 8888 8 8.88 8 8.88 8 8.88 8 8.8 88.8 88 8 88 8 8888 8 8.88 8 8.88 8 8.8 8 8.8 88.8 88 8 8888 8 8.8 8 8.8 8 8.88 8 8.88 88.8 8888 8 8.88 8 8.8 8 8.8 8 8.8 88.8 88 8 88 8 8888 8 8.8 8 8.8 8 8.8 8 8.8 88.8 88 8 8888 8 8.8 8 8.8 88 8.8 88 8.8 88.8 8888 8 8.88 8 8.8 8 8.8 8 8.8 88.8 88 8 88 8 8888 8 8.8 8 8.8 8 8.8, 8 8.8 88.8 88 8 8888 8 8.88 8 8.88 8 8.88 .8 8.8 88.8 8888 8888888888 8888888 8888888 888888 8888888 8888888 11 444444 41] 0.80“ NUQUQUHU QHNOW UQSUNQHH 8w888 cu 8888088888 80 888888888888 8888wu8a8u8o8 m88h Boum 88888uno 8888800 8888888 8088808 8883 8888 88 888888888 88888 88:8 88 88838888 .m 88888 27 Figure 1. Proliferation of buds and reduction of growth in roots of (A) field bindweed and (B) hedge bindweed treated with sub-lethal rates of glyphosate. The control roots are on the left, and the treated roots are on the right. 28 L O R T N O C 29 . .Houucou wood a CH .Houuaoo o: n o .mamom OH ea c m :o mum mwcwumu Hmamw> .ummu mwamu maawuasa m.:moc:n hp Hm>mH Nm mSu um uamummmuw hauamofimwcwwm uoc mum mumuuma aoaaoo suaa mdmmZm m o.o m o.o m o.o m o.o em.m = = m o.o m o.o m o.o a o.o q~.~ m umnsm>oz : o.oH nu m.m o o.e m-o m.¢ cm.m = = wuo m.a mum m.m an N.H mu m.m ¢~.~ «a “unouuo a o.oH aw a.a u m.« mum m.m om.m : : m-o ~.m a-» o.o u m.¢ mu m.a ¢~.~ m “apogee mum a.m mum ~.m a «.0 mum m.a om.m : = a-» m.a a-» w.a a o.o wua e.m ¢~.N mu panaounum mo n.m m-» o.m up o.m wno o.m om.m = = wuo.m.a mum a.¢ u n.n u ¢.m ¢~.~ mN umnaougom «ummonnhau ~H\m n\e ~H\m m\o Amn\wxv Hmuoafiz #0:: Guam cuummuu mama unmaummua onwawumu HouuGOu cums Houunoo vom3cnwn vamfiw mom mummonmhaw mo maouumoflaaam ouammumamumom Hawk .9 manmfi 30 ON «N n NH 0 H aoHon no u o mhmv Hmuoa N H I HN NHI «HI oN « N oN N « 0N «HI «HI NN N H mN N N NN « I HHI «N « I « I «N N H «N ucoauuoua N H NN N I N I NN N o NN « n «N o N I «N N a «N « I N I «N N N NN « N NN unusuaoua « I « I «N « N «N H N I «N N I n I NN « N I NN m a NN n I N I NN o N I NN N H NN « I n I HN H o HN n « HN H « I «N N N «N «H NH «N N o NH N H I NH HH cH NH H I N I «H H I « I «H HH a NH H r N I NH N I N I NH «H «H NH « I N I «H H H I «H NH «H «H N I N I «H «H N «H NH NH NH « I « I «H N o «H uauauuoua «H «H «H N I n I NH a N NH «H NH NH « I o I NH «H o NH NH NH NH N I a I HH « « HH NH HH HH « « I «H « N «H «H a «H N I « I o N N m NH NH o N I N I N N H N unuauaoua «H «H m H I N I N N N N NH NH N N c « « n « N « « H N I n unuamwuua «H NH « NH «H n H I N I « HH oH « NH NH « N H I N «H N N HH HH N N N N N N N « N N N I « I H uonflo>oz N n H u¢AOuoo NH NH H uoaaoamum annHuum onennaaHnm aaanum aooon3¢H£m :HuHuum omuuaauHam Na. 58: N3 58: N8 53. NOV ouauuuonldu Nov auaunuonlua HOV ounuou¢gaoa noHuasou InnHuam «an ooouaaanm nH nuaau>oz «an .uonouuo .uonloumom you «IOH unaua90AIoa .N anuH _31 frost. In the spring of 1977 each crown was green with a profusion of buds at each crown (Figure 2). By August there was complete ground cover and control seen as stunted plants, deformity of leaves, and profusion of buds, but no reduction in stand. These symptoms are similar to those identified in greenhouse studies on field bindweed, hedge bindweed, and buckwheat (Figure 3 and Figure 4). There was a profusion of buds in the leaf axil where normally there would be no stems forming. The leaves are cup shaped and chlorotic. On the mineral soils excellent control of bindweed was obtained throughout the season, while control on the muck soil was only effective early in the season and by late summer many of the plots had as low as 20 percent control (Table 6). Control is usually a little less on high organic soils, however, not 30 to 80 percent lower as is the case here. The tre— mendous decrease in effectiveness on muck soil is attributed to July tillage prior to establishment of the study. It appears that tillage affects the control from glyphosate more on muck soils than it does on mineral soils. Tillage two weeks after treatment appeared to have no effect on bindweed control during the first year (Table 8). By the end of the second season the plowed subplots provided 50 percent less control than the non—plowed except at the high rate of 4.48 kg/ha. By the middle of the third season the plowed subplots provided essentially no control while those not plowed still provided 50 percent control. This probably occurred because plowing after two weeks separated the roots from the source of glyphosate, the tops, resulting in less glyphosate in the roots, therefore, inhibiting their growth for a shorter period of time. 32 Figure 2. Glyphosate was applied to field bindweed at 2.24 kg/ha in the fall. Profuse budding occurred at the crown as observed in the photograph the following spring. 34 Figure 3. Proliferation of buds, deformity, and chlorosis of new leaves in (A) wild buckwheat and (B) field bindweed caused by sub-lethal rates of glyphosate. 36 Figure 4. Proliferation of buds, deformity, and chlorosis of new leaves in (A) hedge bindweed and (B) field bindweed caused ' by sub-lethal rates of glyphosate. 37 .ummu mwcmu mHOHuHDE m.cmoaom ma Hm>oH Nm m:u um ucmuomme NHuamoHMHame uoa mum oumv waHum» m :HSuHB muouumH coaaoo :uHs mammzo .HouucoosNOOH n OH .Houuaoo o: a O monom OH on O m do oumz mmoHumu HmamH>n .mNmH .HN mesh woSOHa «cm mNmH .N wand mwma whoa chHumoHHaam ocHoHnummm 38 nmm.~ m o.o a m.N n m.N m N.m N.a m m.m m m.m mq.e on m.m m N.o a m.N m o.s m w.m m.m m m.m m o.oa e~.~ o m.o m m.o n a.“ m o.s m m.m m.m m m.m m m.m mo.H an ~.m m N.o n m.w m o.s m m.a N.m m o.m m o.m NH.H mummosaaflo «mBOHe «oonm «m30Hm «030Hm «oone «mson «oonm «mach uoz uoz uoz uoz ee\ma\e se\s\a se\ma\m ne\HH\e Amn\mxv unmaummu o mumm m H nwcHumu Houuaou «moz 1 . «omswaHn «HmHm no wummosmNHw mo :oHumoHHmam umumm mxom3 oBu mmeHHu NA «muommwm mm NuHonououhne summonmNHu .w oHan 39 Tillage prior to treatment has been shown to decrease effective- ness of glyphosate (Table 9). It was found that fall tillage and/or spring tillage prior to treatment on June 3, 1977 decreased control obtained from applications of glyphosate on mineral soil by 40 to 70 percent and 30 to 40 percent on muck soil. There was no difference whether tillage occurred in the fall only or fall and spring. This is because the broken roots from tillage lay dormant until spring and did not recover from tillage until then. Fall applications on muck soil provided unsatisfactory control, but excellent control on mineral soil. Tillage after fall treatment either in the fall or in the spring increased the control of the fall treatments by 50 percent on muck soils, and only slightly on mineral soils. When application was not made until July 20, 1977 excellent control was obtained on both muck and mineral soils for all tillage systems, however, the control obtained on the mineral soil was still better than the control on the muck soil. Two years after treatment, excellent control was obtained from glyphosate applied in August, 1975, with or without retreatment (Table 10). Due to cultivation, no control was observed from the spring 1976 treatments. A second application made on October 14, 1976 to those receiving spring application, provided less than 50 percent control one year after the second application. The October treatment was made after corn harvest, therefore, it appears that field bindweed cannot be treated in most situations after corn and soybean harvest. When a second application was applied to those plots having spring treatments in 1976 in the Spring of 1977 excellent control was obtained throughout the season. Except occasional years like 1977, having early springs, field bindweed has not emerged by the middle of May in time 40 .Houucoo NOOH n OH .Houucoo on n O mmHmum OH ou O m do mum mwaHumu HmomH> .ummu mwcmu mHnHuHsa m.amoaoo NA Hw>mH Nm onu um ucmuwmew NHucmoHMchHm no: mum casHoo m :Hsqu mumuumH canoo :uH3 mamm2n .NNOH .ON NHON .NNmH .N m::« .«NmH .mN nonsmummm "meme mums mucmEummuHm m N.O «In O.« Nmuem onuem .mmeHHu wcHuam m O.N m N.N mmeHHu on .Nmumm waHumm «o O.m «u O.m omeHHu waHqu .Nmuam wawumm :Im N.N wlm N.N mmeHHu o: .Nmumm NHDN H 0.0H wlm N.N Noumm NHah .mwMHHHu wcHumm a: m.a sue m.a amuam Nash .mwmflafiu flame H o.oa sum m.¢ Nahum Nana .mmeHHu magnum .mmmHHHs flame wIm N.N on N.N mmeHHu on .Nmumm HHmm am N.N «In N.« Nahum waHumm .omeHHu wcHumm .omeHHu HHmm elm N.N «In N.« Nahum waHumm .oNMHHHu HHmm nlm N.m o N.N mmeHHu waHumm .Nmumm HHmm mum o.m mm m.» «N.N mwmaflsu flame .Nmuam Hana NH\w NH\w HmumCHx xopz Amn\wxv uamaummua .II mummonnNHu mwaHumu Houucoo «mos Houucou «mo3vaHn «Hme now msmumzm wmeHHu ucmHMMMHO :H mumwo£ONHm wo meOHumoHHmnm moamwumamumom .m mHan 41 NOOH u OH .Houuaoo o: n O mmHmum OH ou O m no mum wwaHumu HmomH> .Houucoo .umwu mwcmu onHuHsa m.amuazo Np Ho>oH Nm mnu um unwpmmmHO NHucmonchHm uoc mum :EDHou m aHnuH3 mumuumH canoo nuwa momma .NNmH .mH Nmz .cNmH .eH smnouuo .«NmH .mH muse .mNmH .mH swama< n "OmHHaam mums muomaummuam m 0.0 m 0.0 mcoz II unmaummuu 02 0:02 II uGQEummuu 02 Up mom U mom : A«N.N .. = = @NoN .- .— un «.m «m N.N : NH.H : : : NH.H : : up m.m pm o.~ mamopNom «N.N NN. manuam mammnaom «N.N on. magnum up m.o pm N.H mammpeom NH.H NN. maauam mammnaom NH.H = = m Mom v Co@ : «VNoN : = = : ..NNoN : a. m N.N up m.e smug: NH.H 0N. flame mammn N>mz NH.H 0N. manuam m 0.0 m 0.0 mcmonzom II ucoaummuu oz auoo II unmEummuu 02 U moa U 00a .— .VNoN .- = : QNoN .- .- on N.N « N.N cpoo NH.H «N. HHmm oaoz NH.H : : n w.w U ®.m : ll : : : a«N.N : : on N.N O O.m auoo II uaoaummuu oz cuou NH.H mN. HHmm U QoG @ Qom : A.NNoN .- = N. ..NNoN -— .— on o.a c m.m cuoo NH.H ON. HHmm mammnNom NH.H = = U mo@ U 60¢ = -— «N.N p. = = A.VNoN .- N— on N.N v N.m mums; N>mz NH.H NN. magnum auoo NH.H ma. Hana m~\m mH\m ANNmHV Amn\wxv emummuu Aoemav Amn\wxv gunman“ mwawump vooz aouu mumm mummy echo oumm mummw mrI GOHumuou omega «an .mqmon N>ma .mamonzom .auoo m :H Houucou mooBmaHn «HmHm now mummonehHw «o mmOOHumoHHmmm moamwumEoumom .OH oHan 42 to be treated prior to seed bed preparation for corn and soybeans. Navy beans, however, are planted late enough in June to allow emergence and growth of field bindweed and glyphosate treatment prior to seed bed preparation. Fall treatments cannot be applied following corn and soybeans due to late fall harvesting, cold temperatures at that time, and harvesting techniques which destroy all or part of the field bindweed foliage. Post harvest applications of lyphosate are best adapted to wheat. In summary, glyphosate is an effective chemical for controlling field bindweed, however, the roots are only inhibited for two or three seasons after treatment so eradication with one application of gly- phosate is not very probable. Retreatment after the second season is necessary to have continual control. Glyphosate can be applied any time _ during the growing season after flower bud initiation through late fall. Fall applications are effective as long as continuous or extremely low temperatures do not follow treatment. Tillage prior to treatment can completely eliminate glyphosate phytotoxicity, if it occurs close to treatment. Tillage after treatment increased control during the first season with fall applications in marginal control situations, but decreased control after spring treatments during the second season. 10. 11. 12. l3. 14. 43 Literature Cited Agbakoba, Chuma S. O., and J. R. Goodin. 1970. Picloram enhances 2,4-D movement in field bindweed. Weed Sci. 18:19-21. Baird, D. D., R. P. Upchurch, W. B. Homesley, and J. E. Franz. 1971. Introduction of a new broad spectrum postemergence herbicide class with utility for herbaceous perennial weed control. Proc. N. Cent. Weed Control Conf. 26:64-68. Bakke, A. L. 1939. Experiments on the control of European bind- weed (Convolvulus arvensis L.) Agr. Expt. Sta., Iowa State Coll. Agr. Research Bull 294. Bakke, A. L. 1944. Control and eradication of European bindweed. Iowa State College of Agric. Exp. Sta. Bull. P61. pp. 937-960. Best, K. F. 1963. Note on the extent of lateral spread of field bindweed. Can. J. Plant Sci. 43:230-232. Bioletti, Frederic T. 1911. The extermination of morningglory. University of California College of Agric. Circ. No. 69. pp. 1-12. Call, L. E. and R. E. Getty. 1923. The eradication of bindweed. Kansas Agr. Exp. Sta. Cir. 101. Cox, H. R. 1908. The eradication of bindweed or wild morning- glory. USDA Farmers Bull. 368. Davison, J. G. and J. A. Bailey. 1974. The response of Convolvu- lus arvensis (bindweed) to 2.4-D, MCPA, MCPB, Dichloroprop, Mecoprop, 2,4,5-T Dicamba and glyphosate at various doses and application dates. Proc. Brit. Weed Control Conf. 2:641-648. Derscheid, Lyle A., J. K. Stritzke, and Wayne G. Wright. 1970. Field bindweed control with cultivation, cropping, and chemicals. Weed Sci. 18:590-596. Derscheid, Lyle A., and Keith E. Wallace. 1959. Control and elimination of field bindweed. South Dakota Exp. Sta. Circ. 146. pp 0 1-4 0 Fischer, B. B., F. H. Swanson, D. M. May, A. H. Lange. 1976. Roundup review. Agrichemical Age, June 1976. pp. l6, 17, 21. Frazier, J. C. 1943. Nature and rate of development of root systems of Convolvulus arvensis. Botan. Gaz. 104:417-425. Frazier, John C. 1948. Principal noxious perennial weeds of Kansas, with emphasis upon their root systems in relation to control. Kansas State College of Agricu. Exp. Sta. Bull. 311. pp.L45. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27- 28. 29. 30. 44 Harvey, W. A. 1965. Costs and losses from weeds. Proc. 17th Hamilton, W. D., A. H. Lange, C. L. Elmore. 1971. Field bindweed control in vineyards. Calif. Agr. 25(9):9-10. Higgins, Robert E. 1967. Loss caused by noxious weeds in potatoes. Down to Earth 23(1):2, 24. ‘ Jones, I. B., and J. 0. Evans. 1973. Control of Russian knapweed and field bindweed with dicamba, 2,4-D and their combinations with and without DMSO. Proc. West. Soc. Weed Sci. 26:39-43. Kennedy, P. B., and A. S. Crafts. 1931. The anatomy of Convolvu- lus arvensis, wild morningglory or field bindweed. California Agric. Exp. Sta. Bull. No. 5:591-622. (Hilgardia). Kiesselbach, T. A., N. F. Peterson, and W. W. Burr. 1934. Bind- weeds and their control. University of Nebraska College of Agric. Exp. Sta. B11110 2870 1-470 Kiesselbach, T. A., P. H. Stewart, and D. L. Gross. 1935. Bindweed eradication. Nebraska Exp. Sta. Circ. 50:1-8. Kleifeld, Y. 1972. Control of annual weeds and Convolvulus arvensis L. in tomatoes by trifluralin. Weed Res. 12:384-388. Kline, W. L., and G. W. Selleck. 1977. Effect of glyphosate applications on hedge bindweed. Proc. N. E. Weed Sci. 31:98. Lange, A. H., B. Fischer, H. Agamalian, H. Kempen. 1969. Weed control in young crops. Calif. Agr. 23(9):1l-12. Lange, A. H., B. B. Fischer, C. L. Elmore, H. M. Kempen, J. Schlesselman. 1975. Roundup-—The end of perennial weeds in tree and vine crops? California Agriculture. pp. 6-7. Leonard, O. A., D. E. Bayer and R. J. weaver. 1961. Results of tests using 2,4-D in vineyards. Hormolog. 3:10-11. Mitch, L. W., B. L. Bohmont, H. P. Alley, and N. E. Harrington. 1962. Wyomings primary noxious weeds. Bull. Wyoming Agric. Exp. Sta. 394, p. 40. ' Neuruer, H. 1961. Weeds which hinder combine harvesting. Pflanzenarzt. 14:61-63. Phillips, W. M. and F. J. Timmons. 1954. Bindweed, how to control it. Kansas Agr. Exp. Sta. Bull. 366. Roncoroni, E. J., C. L. Elmore, A. H. Lange. 1976. Thin layering of herbicides for field bindweed control in established orchards and vineyards. Proc. West. Soc. Weed Sci. 29:195-201. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 45 Seely, C. E., K. H. Klages and E. G. Schafer. 1944. Bindweed control. wash. Agr. Exp. Sta. Popular Bull. 176. Sripleng, Aksorn, and Frank H. Smith. 1960. Anatomy of the seed of Convolvulus arvensis. American Journal of Botany. 47:386-393. Stewart, George, and D. W. Pittman. 1924. Ridding the land of wild morningglory. Utah Agric. Exp. Sta. Bull. 189. 1-30. Sylvester, E. P. 1947. Soybeans as a smother crop for European bindweed. Iowa State College of Agri. Bull. warner, L. C. 1973. Subsurface layering of trifluralin with a moldboard plow for field bindweed control. Proc. West. Soc. weed Wiese, A. F. 1969. Perennial weed control in northwest Texas. Texas Agr. Exp. Sta. MP-828. pp. 1-4. Wiese, A. F. 1971. Mbnuron and other soil sterilants for controlling small patches of perennial weeds. Texas Agr. Exp. Sta. PIP-1002. pp. 1-70 Wiese, A. F., and W. M. Phillips. 1976. Field bindweed. Weeds Wiese, A. F., and H. E. Rea. 1955. Bindweed control in the pan- handle of Texas. Texas Agri. Exp. Sta. Bull. 802. pp. 3-8. Withycombe, R. 1911-12. Report of the Department of Agronomy. Oregon Agri. Exp. Sta. Report East, Oregon Station. CHAPTER 3 EFFECT OF DILUENT VOLUME AND CALCIUM ON GLYPHOSATE PHYTOTOXICITY} Abstract The effects of diluent volume and calcium concentration on glyphosate[N-(phosphonomethyl)glycine] phytotoxicity were evaluated by applying 0.0, 0.0025, 0.005, 0.01, 0.02, and 0.04 M C301 and 1.68 kg/ha 2 glyphosate at 130, 190, 375, and 750 L/ha to tall morningglory [Ipomoea purpurea (L.) Roth] plants 10 to 12 cm tall. Thirty days after treatment, plant height and fresh and dry weight measurements showed that calcium reduced glyphosate phytotoxicity at high applica- tion volumes. However, at 190 L/ha calcium concentrations up to 0.01 M did not cause a reduction of glyphosate phytotoxicity. Increasing the diluent volume above 190 L/ha decreased glyphosate phytotoxicity. Addition of a sulfonine red dye to the spray solution indicated that at 130 and 190 L/ha, runoff from the annual morningglory leaves was negligible. At 375 L/ha or greater diluent volumes. 1/2 to 3/4 of the spray solution as measured by dye retention ran off the leaf surface. At 750 L/ha the spray pattern on the leaf surface was not uniform as the water and dye collected at the leaf margins. Addition of isopropyl- amine to formulated glyphosate did not counteract the reduction of glyphosate phytotoxicity caused by calcium. 46 47 Introduction Glyphosate was introduced as a herbicide in 1971 (1). It provides wide spectrum weed control, and due to phloem translocation to the meristematic regions of the foliage and the root systems, it provides excellent perennial weed control (9). There has been interest in combining glyphosate in tank mixes and split applications with other chemicals such as atrazine [2-chloro-4-(ethylamino)-6-(isopropylamine)- g-triazine], propachlor (2-chloro-N-isopropylacetanilide), terbacil (3-Egggybutyl-S-chloro-6-methyluracil), simazine (2-chloro-4,6-bis (ethyl-amino)-§-triazine), amitrol (3-amino-g-triazole), and other wettable powders, especially for no-till applications (5, 8). When combined with certain wettable powders, glyphosate was no longer active (3). Phillips (5) reported that atrazine, propachlor, and non-herbi- cidal wettable powders decreased glyphosate phytotoxicity on sorghum (Sorghum vulgare Pers.). Selleck (9) found amitrol and simazine reduced activity of glyphosate on smooth bromegrass (Bromus inermis L.) when sprayed as a tank mix; however, there was no antagonism when sprayed separately the same day or later. He also showed that bromacil (5-bromo-3-§gg-butyl-6-methyluracil), diuron (3-(3,4-dichlorophenyl)-1, l-dimethylurea), and amitrol reduced glyphosate toxicity to common milkweed (Asclepias syriaca L.) and bouncing bet (Saponaria officinalis L.). Amitrol did not reduce control of toadflax (Linaria vulgaris Hill.) when tank mixed with glyphosate as did all other herbicides tested. No antagonism was seen in combination with any of the herbi- cides on bluegrass (Poa pratensis L.), goldenrod (Solidago spp. L.) or brambles (Rubus spp. L.). Combinations of glyphosate with liquid nitrogen gave enhanced kill of winter rye [Secale cereale (L.) var. 48 Balboa] (4). Nitrogen fertilizers only enhanced the initial injury with complete recovery in 6 weeks on perennial sod species. Peters et al. (3) also shows that complete fertilizers reduced glyphosate activity. Calcium, iron, zinc, and aluminum have been shown to reduce glyphosate phytotoxicity (3, 5, 7, 13), whereas Wills (13) reported potassium, sodium, ammonium, and calcium increased glyphosate activity in descending order on purple nutsedge (Cyperus rotundus L.). Ammo- nium sulfate appeared to activate glyphosate either in a tank mix or when applied separately (2, 10, ll). Cations tended to reduce glyphosate activity, whereas anions had little or no effect on activity (5, 13). High diluent volumes also reduced glyphosate activity both in the field and in the greenhouse (5, 6, 7, 14). Increasing the addi- tional surfactant concentration above that in the formulation pro- duced variable results; however, the negative effect of high diluent volume was partially overcome (6, 7, 14). Our studies were designed to determine the effects of diluent volume and calcium concentration on glyphosate phytotoxicity and determine the volume and calcium concentration offering maximum phytotoxicity. We were also interested in interactions between diluent volume and calcium. Since high diluent volume alone de- creased glyphosate control, a study was designed to determine the diluent volume at which runoff became a factor in reducing activity of glyphosate. 49 Materials and Methods The effects of diluent volume and surfactant levels on gly- phosate activity were studied in the field in 1975 on quackgrass [Agropyron repens (L.) Beauv.] and in 1977 on field bindweed (Convolvulus arvensis L.). The quackgrass was treated May 20, 1975 at 25 to 30 cm height with diluent volumes of 140, 280, and 560 L/ha and additional surfactant at 0.25 and 0.5 percent was added to the 365 g/L acid equivalent formulation of glyphosate on a volume—to-volume basis. The field bindweed was treated at full bloom on June 15, 1977 with diluent volumes of 93, 186, 280, and 560 L/ha. No additional surfactant was applied in this study. Glyphosate was applied at rates of 0.56, 0.84, and 1.12 kg/ha to quackgrass and at 0.56, 0.84, 1.68, and 3.36 kg/ha to field bindweed. Variable diluent volumes were obtained by changing nozzle sizes, application speed, and pressure. All treatments were made with a tractor-mounted sprayer. To evaluate the effects of diluent volume and calcium on glyphosate phytotoxicity in the greenhouse, tall morningglory was grown in 946-ml wax-covered cups using greenhouse potting soil with 10 percent organic matter. Five tall morningglory seeds were planted in each pot and thinned to three uniform plants after emergence. The plants were fertilized twice weekly with a commercial fertilizer containing an analysis of 20-20-20 NPK. The test plants were grown in the greenhouse with supplemental lighting to provide a 14-hour day. Glyphosate was applied to the tall morningglory plants when they were 10 to 12 cm tall. Glyphosate was applied at 1.68 kg/ha with 0.0, 0.0025, 0.005, 0.01, 0.02, and 0.04 m CaCl and dilution 2 volumes of 130, 190, 375, and 750 L/ha were obtained by changing nozzle 50 size and pressure. The plants were harvested 30 days after treatment and plant fresh and dry weights measured. The data were analyzed as a two-way factorial design and presented as the means of three experiments with four replications per experiment. Tall morningglory plants, 20 to 25 cm tall, were used in a study designed to determine the diluent volume at which runoff became a factor in reducing glyphosate activity. The methods for growing the test plants were the same as in the previous study. Diluent volumes of 130, 190, 375, and 750 L/ha and calcium concentrations of 0.0, 0.0025, 0.01, and 0.04 m as CaCl2 were combined with glyphosate a at 1.68 kg/ha for evaluation of spray retention on the leaf surface. Sulfonine red dye was added to the spray solution at a concentration of 2 g per 500 ml of the spray mixture. The spray remaining on the leaf surface was either washed off the leaves immediately with de- ionized water and collected in SO-ml beakers or allowed to dry and then washed off with deionized water and collected in 50-ml beakers. All samples were brought to equal volume and absorbance measured spec- trophotometrically at 430 nm and absorbance related to leaf area. Treated leaves were photographed while wet and after drying. The data presented are the means of two experiments with four replications per experiment. A study was designed to determine if calcium and isopropylamine, the salt used in formulating glyphosate, were competing for the same site on the glyphosate molecule. Tall morningglory plants grown as above to 12 to 15 cm in height were sprayed with glyphosate at 1.12 kg/ha, calcium.at 0.0 and 5.9 M, and isopropylamine at 0.0, 0.25, 0.5, and 1.0 percent by volume. The isopropylamine was added to the 51 formulated glyphosate or the water if glyphosate was absent. This mixture, together with the calcium, was then added to the spray mixture. Plant height and fresh and dry weights were determined after 45 days. The data presented are the means of two experiments with four replications each. _Results and Discussion Two field studies, one on quackgrass and the other on field bindweed, showed 40 to 50 percent decrease in the control of quack- grass and field bindweed with glyphosate as the diluent volume increased to 560 L/ha (Table 1). Additional surfactant increased glyphosate phytotoxicity only at the 1.12 kg/ha herbicide rate and 560 L/ha diluent volume; however, it did not completely remove the loss of phytotoxicity due to increased diluent volumes. In the green- house diluent volume did not reduce glyphosate activity until the volume was greater than 190 L/ha (Table 2), similar to the field studies (Table 1). No difference in plant height and weight was evident between the 130 and 190 kg/ha rate, but a significant in- crease was evident when the volume was increased to 375 and 750 kg/ha. Considering calcium averaged over all of the diluent volumes, even the 0.0025 M inhibited glyphosate activity (Table 3). Con- sidering fresh and dry weight, a calcium concentration of 0.01 M or greater appeared to render glyphosate inactive; however, with respect to plant height, calcium did not totally inactivate glyphosate at any of the concentrations tested. These results were due to the profusion of buds which occurred after treatment, which increased .Honuaoo muoHeaoo I OH .Houunoo on n O .mHmom OH cu O o no mwnHumu Hmde> .ummu mmsmu mHmHuHaa m.smoada an Ho>mH Nn mam um unmummmHv NHunmUHmHome uoa mum umuuoH meow one No «oBOHHou mousse .aOHumHoauom mummozoNHw onu nH NvmouHm umnu ou wovvm NHHO sozv unmuomwuom HddOHqum unmaHHn xIw O.« xIH N.N x N.N N.O NH.H film N.N filo N.N fix N.N mN.O NH.H OI; N.N xlm N.N Hx N.N 0.0 NH.H mIo N.« 3n N.N xIn m.« m.O «0.0 «no m.¢ gum n.m x-» «.9 m~.o ew.o OIL N.N mIn N.N nlo N.« m.O «0.0 o N.H «In N.N «It N.N mN.O «N.O m o.H on o.m x-» w.m o.o em.o o 0.0 m 0.0 0.0 0.0 «m.O nfimwnHuou Houunoo woos mmmuwxoooov com emu can A.Ho> NV Awa\mxv muamuommuSN mummonthO Amn\uv mauHo> samsHan «HmHm onu dH macaw «moBOan vaHm mam ammuwxomou ou NuHUonuouhza cannonnNHw do uamuomuusm HmoOHquvm mam oaaHo> ucooHHv mo uoommo may .H mHnma 53 Table 2. Effects of diluent volume on glyphosate phytotoxicity at 1.68 kg/ha on tall morningglory 10 to 12 cm in height grown in the greenhouse Diluent volume Plant heighta Fresh weighta Dry weighta (L/ha) (cm/ plant) (3/ plant) (g/Plant) 130 22.9 a 4.2 a 0.8 a 190 30.2 a 5.0 a 0.9 a 375 41.3 b 6.1 b 1.0 b 750 51.0 c 7.7 c 1.2 c aMeans within the same column followed by the same letter are not significantly different at the 5% level by Duncan's multiple range test. 54 .umou owamu MHOHuHsa m.amoaon Np Hm>oH Nm onu um ucouowva NHunmonHanm uoa mum nouuoH mamm can he mosoHHom naoHoo mama mnu anuHa mammzd m « N.H m N.N O «.ON II Houudoo «u H.H ow O.N o N.O« «0.0 «0 H.H om w.« 0 «.ON N0.0 «0 H.H mo O.N on O.HN H0.0 on O.H on «.m a «.mN NO0.0 m m.O n m.« n O.NN mNO0.0 m «.O m N.N om «.NH 0.0 m«.H AgamHm\wv AquHm\wv AuomHONEUV sz Am:\wxv uanoa Nun ouanma :moum uanos uomHm asHoHoo mummonnhHo m omsonnoouw osu dH macaw NuonwaHnuoa HHmu ou NuHonououNne cosmonONHw so aoHono mo muoowmo ona .N oHnma 55 fresh and dry weight of the plants but did not increase their height. A definite reduction of glyphosate phytotoxicity due to high diluent volume was evident (Table 4). Using deionized water as the carrier, no reduction in control was observed in plant height as the diluent volume was increased until the diluent volume was 375 L/ha or greater. Addition of 0.0025 M calcium to the glyphosate mixture caused a reduction in control at 375 L/ha, 0.02 M calcium caused a reduction at 190 L/ha, and 0.04 M calcium caused a reduction at 130 L/ha (Table 4). According to U.S. Department of Interior (12) very few areas in the United States have water with concentrations of calcium greater than 0.0025 M, a few were found to have concentrations of calcium up to 0.005 M, and only one location in New Mexico had a concentration of calcium as high as 0.01 M. Therefore. glyphosate inactivation due to high calcium concentrations are uncommon. Sulfonine red dye was used to measure spray runoff from the leaf surface to determine the critical diluent volume at which runoff became a factor. As the diluent volume was increased from 130 to 190 L/ha, spray retention, as determined by absorbance, increased from 0.0076 and 0.0136 O.D./cm2 (Table 5). Since the dye concentration in the water was the same, the dye retained should have doubled as diluent volume increased from 190 L/ha to 375 L/ha; however, this did not occur. Thus runoff became a factor in the reduction of glyphosate phytotoxicity only if the diluent volume was greater than 190 L/ha. Similarly in the field 93, 140, and 186 L/ha diluent volumes caused no reduction in phytotoxicity, but 280 L/ha and greater caused a significant reduction. The photographs in Figure 1 indicate that the 130 L/ha diluent volume treatment resulted in uniform spray droplets 56 .ummu mwsmu oHaHuHsa m.dmoaon Np Ho>mH Nm onu um unwuomeO NHuamonchHm uoo mum HouuoH mamm mnu he moBOHHom mcmozm o N.«« o m.w« o N.Nm o H.«« o N.Hm oIo 0.0N ONN m «.«« m N.N« m N.«« «I0 N.NN mIo N.NN no O.HH NNN mm «.H« o «.O «In «.OH. m O.N m H.m m N.N OOH mIo N.ON UIm N.«H m m.« on 0.0H m N.N m O.N ONH AuGMHn\aov AuamHa\aov AuaMHe\aov AuamHm\aov AusMHO\Eov AudMHO\EUV ustms usmHm uanms uanm uanm: uane uawHon udem uanms uanm uanon uamHm Amn\HV «0.0 N0.0 H0.0 NO0.0 NNO0.0 0.0 masHo> usooHHO «Hay Naomo mm a5HUHmo omsonammum osu aH n3oum uanm: NHOwacHnuoa HHmu so ma5H0> usmsHHw mam EDHUHmo mo cOHuomumucH onH .q manna 57 Table 5. The influence of calcium.an the retention of sulfonine red dye on the leaf surfaces of tall morningglory grown in the greenhouse Diluent volumes Calcium Absorbancga (L/ha) (M) (O.D./cm ) 130 0.0 0.0076 a 190 0.0 0.0136 bc 375 0.0 0.0147 cd 750 0.0 0.015 ed 130 0.0025 0.0097 ab 130 0.015 0.008 a 130 0.04 0.0088 a 750 0.0025 0.0111 a-c 750 0.01 0.019 d 750 0.04 0.016 cd aMeans followed by the same letter are not significantly different at the 5% level by Duncan's multiple range test. 58 Figure l. Glyphosate and sulfonine red dye retention on tall morning- glory leaves when applied at 130 and 750 L/ha and photo— graphed while wet and dry. (A) 130 L/ha wet, (B) 130 L/ha dry, (C) 750 L/ha wet, (D) 750 L/ha dry. 59 60 on the leaf surface compared to the 750 L/ha rate which deposited large spots that ran off the leaf surface. Very little of the spray mixture was retained at 750 L/ha. No decrease in spray retention was observed either visually or by absorbance of dye retained when calcium was added to the spray mixture (Table 5). Additional isopropylamine was added to the isopropylamine for- mulation of glyphosate to determine the competitiveness of isopro- pylamine and calcium for the same site on the glyphosate molecule. Additional diluent, if the water contained calcium, would increase the amount of calcium available for inactivating glyphosate. Thus, if high concentrations of calcium were present in the water, additional isopropylamine should counteract the additional calcium; however, the data in Table 6 indicates that there was no difference in glyphosate phytotoxicity as the isopropylamine rates varied from 0 to 1 percent either in deionized water or 5.9 M calcium mixture. Either they did not compete for the same site on the glyphosate molecule or additional isopropylamine could not replace the calcium. In summary, calcium in the spray water does not appear to be a problem in reducing glyphosate phytotoxicity as long as the diluent volume is less than 185 L/ha. .umou swoon mHOHana m.cmoa:O Np Hw>mH Nm onu um uaouoNMHm NHuamUHdeme no: can HouuMH mama mnu Na «maoHHow chQZA .mummonmNHw mo dOHuMHoauow udem>Havm vHow H\wx «N.O o£u dH uaooam ozu ou oOHquvm nH mH comma onHawHNnouaomH mo mMNMudmoumm mnam 61 «0 NN.O on «.m on N.ON O.H 0.0 0.0 v NN.O o H.« « N.OOH n.O 0.0 0.0 «on NN.O on w.« on m.m« NN.O 0.0 0.0 «on «w.O on N.N «u «.Hm 0.0 0.0 0.0 and «.O no «.« no m.«« O.H «O.N NH.H pm N«.O no «.N no «.NN m.O «O.N NH.H cam NN.O no O.N no N.ON NN.O «O.N NH.H «one NN.O and m.« o m.«N 0.0 mm.m NH.H «and NN.O pm O.N one N.NN O.H 0.0 NH.H m N«.O m N.N o N.NN «.O 0.0 NH.H no N«.O m H.N m «.«N NN.O 0.0 NH.H no Hn.O no O.N m «.NN 0.0 0.0 NH.H 351:3 35:33 35333 8 O3 35me pustoa Nun nuanms amoum nuston udMHm mmaHamHNnoumomH adHono mummonaNHO NHOwanHauoa HHou ou NuH>Huom mummonnhHw do EOHUHmo «do aOHuMHoauom Hmauos was sH umsu o>ono ocHEMHNnounomH HmsOHquum mo noHuomuouuH msfi .« mHomH 62 (Literature Cited Baird, D. D., Upchurch, W. B. Homesley, and J. E. Franz. 1971. Introduction of a new broad spectrum postemergence herbicide class with utility for herbaceous perennial weed control. Proc. North Cent. Weed Contr. Conf. 26:64-68. Blair, A. M. 1975. The addition of ammonium salts or phosphate ester to herbicides to control Agropyron repens (1.) Beauv. Weed Res. 15:101-105. Hanson, C. L. and C. E. Rieck. 1976. The effect of iron and aluminum on glyphosate toxicity. Proc. South. Weed Sci. Soc. 29:49. Peters, R. A., W. M. Dest, and A. C. Triolo. 1974. Preliminary report on the effects of mixing liquid fertilizers and residual herbicides with paraquat and glyphosate. Proc. N. E. Weed Sci. Soc. 28:35-40. Phillips, W. M. 1975. Glyphosate phytotoxicity as affected by carrier quality and application volume. Proc. North Cent. Weed Contr. Conf. 30:115. Riemer, D. M. 1973. Effects of rate, spray volume, and surfac- tant on the control of phragmites with glyphosate. Proc. N. E. Weed Sci. Soc. 27: 101-104. Sandberg, C. L., W. F. Meggitt, and D. Penner. 1976. Influence of spray volume and calcium of glyphosate phytotoxicity. Proc. North Cent. Weed Contr. Conf. 31:31. Selleck, G. W. 1975. Antagonistic effects with glyphosate herbicide plus residual herbicide combinations. Proc. N. E. Weed Sci. Soc. 29:327. Sprankle, P., W. F. Meggitt, and D. Penner. 1972. Absorption, action, and translocation of glyphosate. Weed Sci. 23:235-240. Suwunnamek, U. and C. Parker. 1975. Control of Cyperus rotundus with glyphosate: the influence of ammonium sulphate and other additives. Weed Res. 15:13-19. Turner, D. J. and M. P. C. Loader. 1975. Further studies with additives: effects of phosphate esters and ammonium salts on the activity of leaf-applied herbicides. Pestic. Sci. 6:1-10. U.S. Department of Interior. 1966-1970. Quality of Surface Waters of the United States. Paper Nos. 2144, 1-367; 2146, 1-540; 2109, 1-633; 2157, 1-532; 2149, 1-349. 13. 14. Wills, G. D. of glyphosate p. 59. Wills, G. D. 63 1973. Effects of inorganic salts on the toxicity to purple nutsedge. Abstr. Weed Sci. Soc. Amer. 1973. Toxicity of glyphosate to purple nutsedge as affected by surfactant K200 and diluent volume. Proc. South. Weed Sci. Soc. 26:408-412. 3 CHAPTER 4 ABSORPTION, TRANSLOCATION, AND METABOLISM OF 14C-GLYPHOSATE IN SEVERAL WEED SPECIES Abstract 14 The pattern and extent of C-glyphosate [N-(phosphonomethyl) glycine] translocation from the treated leaf and metabolism of 14C-glyphosate was studied in field bindweed (Convolvulus arvensis L.), hedge bindweed (Convolvulus sepium L.), Canada thistle (Cirsium arvense (L.) ScOp.), tall morningglory (Ipomoea purpurea (L.) Roth.) and wild buckwheat (Polygonum convolvulus L.) that received a 0.2 to 0.3 uCi drop of l4C-glyphosate on a leaf midway on the parent stem. 14C was translocated throughout the plants within 3 days; the greatest concentration accumulated in the meristematic tops of the roots and shoots. 14C was localized in the phloem in cross and longitudinal sections of stems and roots. Minor, but significant, relocation occurred in Canada thistle and wild buckwheat after 3 days. Of the 14C applied to the treated leaf, field bindweed translocated 3.5 percent, hedge bindweed 21.6 percent, Canada thistle 7.8 percent, tall morningglory 6.5 percent, and wild buckwheat 5 percent. Metabolism studies in field bindweed, Canada thistle, and tall morningglory indicated very little metabolism of the parent glyphosate. Amino- methylphosphonic acid was the major metabolite found, making up less than 15 percent of the total 140. Of the total 14C applied to excised 64 65 leaves, 50 percent had disappeared within 25 days. Neither translo- cation nor thin layer chromotography of the metabolites could account for this loss. Introduction Glyphosate is a broad spectrum postemergence herbicide (l, 2, 5, 6, 8). Although glyphosate is active on most perennial weed species, the control of specific species such as field bindweed may be less than desired under certain environmental and tillage conditions. Glyphosate is absorbed and translocated in the phloem in both annual and perennial weeds (2, 3, 4, 7, 13, 16, 18). Translocation is rapid; however, tillage of treated quackgrass (Agrgpyron repens (L.) Beauv.) after 1 day allowed more buds to survive than tillage after longer time intervals (3, 4, 13). The contribution of glyphosate metabolimm to the variability in perennial weed control is not know. However, very little metabolism of glyphosate has been found in plant material (7, ll, 18). Glyphosate is broken down in soil and water to C02 (9, 10, 12, 14). Aminomethylphosphonic acid (AMP) was the major metabolite isolated from both soil and plants (7, 10, 11). The objectives of this investigation were to study absorption, translocation, and metabolism of glyphosate by Canada thistle and field bindweed. Because a number of viney weed species are often confused with field bindweed, hedge bindweed, a perennial, and tall morningglory and wild buckwheat, both annuals, were also included in several of the studies for comparison. 66 Materials and Methods For absorption and translocation experiments tall morningglory, 'Clarke's Heavenly Blue', and wild buckwheat were planted three seeds per 946-ml wax cup filled with 860 g of white quartz sand and thinned to one plant per pot after emergence. Field bindweed and Canada thistle were grown from root cuttings 8 to 10 cm long and hedge bind- weed from root cuttings 12 to 15 cm long. Each root cutting had a large shoot (hereafter referred to as the parent plant) at one end and a smaller or less mature shoot at the other end (hereafter referred to as the daughter plant). The parent plant received the 14C-glyphosate treatment. Root cuttings were planted 6 cm deep in 946-ml wax cups with 860 g of white quartz sand. The sand was saturated with modified Hoagland's No. 1 solution and sub-irrigated throughout the experiment with the same. Plants were grown under supplemental lighting giving 16-hour days. The temperature was maintained at 25 1:2 C. Plants received a 5 um drop containing 0.2 uCi of 14C-glyphosate on a leaf midway along a parent stem. The 14C-methyl-labeled glyphosate (spec. act. = 1.51 mCi/mmole, purity 95% by TLC) was converted from acid to the isopropylamine salt by addition of 4 ul of isopropylamine to 4.4 mg of acid followed by the addition of 1.0 m1 of deionized water and 0.8 percent MON 0818 (nonionic polyethoxylated tallow amine) surfactant for all experiments. Treatments were applied when field bindweed and hedge bindweed shoots were 18 to 20 cm long, Canada thistle 14 to 18 cm, tall morningglory 12 to 14 cm, and wild buckwheat 16 to 18 cm. Plants were harvested 3 and 14 days after treatment, those used for radioautography were immediately frozen with dry ice, freeze-dried, rehydrated, mounted, and radioautographed. (The radioautographs 67 represent each harvest time and plant species from two experiments with two replications each.) Stems and roots used to determine where the 14C-glyphosate was located in the vascular system were cut into cross and longitudinal sections at harvest prior to freezing. Plants to be oxidized were dissected into several parts. Field bindweed, hedge bindweed, and Canada thistle were dissected into above treated leaf, below treated leaf, root, daughter plant, and treated leaf. Tall morningglory and wild buckwheat were dissected into above treated leaf, below treated leaf, root, and treated leaf. Plants were freeze- dried and then pulverized with a mortar and pestle. .A representative sample was combusted by the Schoeniger method of Wang and Willis (17) to determine by liquid scintillation radioassay the quantity of 14C translocated to each plant part. The combustion data were analyzed as a two-way factorial with two replications. To determine the amount of applied 14C-glyphosate that left the treated leaf, the total 14C in all plant parts excluding the treated leaf were added together and divided by the total 140 applied. Field bindweed, Canada thistle, and tall morningglory plants for metabolism experiments were grown as described above. When the plants were 10 to 12 cm long, they received a 5 ul drop containing 0.125 uCi of isopropylamine salt of 14C-glyphosate on each of two leaves midway on the parent stem. Field bindweed and Canada thistle were harvested at 3, 7, and 30 days and tall morningglory 1, 7, and 21 days after treatment. Field bindweed and Canada thistle and tall morningglory as described above were dissected. Plant parts were immediately placed in dry ice and kept in the freezer at -10 C. The samples were homogenized in a Sorvall omni-mixer in 10 to 20 ml of glass distilled acetone to 68 remove chlorophyll and other acetone-soluble substances. The maserates were centrifuged at 17,300 x G at 0 to 3 C and washed three or more times with acetone until no green color remained in the acetone frac- tion. Less than 1 percent of 14C was lost in the acetone fraction. They were then washed three times with 30 ml of deionized water. The procedure was 85 percent efficient in extracting the 14C-glyphosate. The 90-ml water sample was concentrated to approximately 0.5 ml. The concentrated liquid was removed from the evaporation flask and a 20 ul sample was assayed by liquid scintillation radioassay to determine the total radioactivity for each sample. A 20 ul sample was removed from the 0.5-ml sample and spotted on 500 um thick cellulose TLC plates and chromatographed with a standard containing glyphosate, AMP, glycine, and sarcosine. The plates were developed with a solvent system of 55 ml ethanol, 35 ml water, 2.5 ml of 15 N ammonium hydroxide (NHAOH), 3.5 g trichloroacetic acid (TCA), and 2 m1 acetic acid (15). The standard was sprayed with ninhydrin, placed in an 80 C oven, then radioautographed. The Rf values of the mixture were: glyphosate 0.28 to 0.32, AMP 0.4 to 0.44, glycine 0.54 to 0.58, and sarcosine 0.68 to 0.72. Following radioautography, the radioactive spots on the plates from the 14C-glyphosate metabolism study were removed for quantative assay by liquid scintillation radioassay. Loss of 14C-glyphosate from the treated leaf was determined by using field bindweed and tall morningglory leaves excised from the plant and spotted with 0.3 uCi of 14C-glyphosate. Leaves were kept in an aluminum tray at 25 C until combustion at O, l, 6, and 12 hours and l, 2, 3, 11, 18, and 25 days. Radioactivity was determined by liquid scintillation radioassay. The treatments in the excised leaf study 69 were replicated four times and completely randomized. All data presented are means of two experiments with two to four replications each. Results and Discussion There are certain inherent problems in the measurement of foliar absorption of herbicides including incomplete removal of nonabsorbed or bound herbicide on the surface of the leaf and the elution of herbicide already absorbed by washing the leaf with various solvents. Using techniques involving the removal of the 14C-glyphosate treated spot from the leaf or washing the leaf surface after treatment, past research has shown foliar absorption of glyphosate to be 25 to 50 per- cent of the amount applied (13, 18). The efficacy for perennial weed control of a phloem translocated herbicide such as glyphosate is related to stage of plant growth, sink-source relationships and the amount of herbicide absorbed. By measuring the amount of 14C that moved out of the treated leaf under controlled conditions over a period of time, it appeared that absorption of glyphosate did not continue beyond 3 days after treatment in field bindweed, hedge bindweed, and Canada thistle (Table 1). Tall morningglory and wild buckwheat, however, did show additional absorption and movement out of the treated leaf after 3 days (Table 1). Hedge bindweed absorbed and translocated considerably more ll‘C-glyphosate from the treated leaf than the other species. Experiments designed to localize the movement of the 14C label showed that significant basipetal translocation of 14C occurred in both Canada thistle and wild buckwheat between 3 and 14 days after treatment (Table 2). This translocation was not evident 70 .ummu H .muaovoum ago he Ho>mH Nm on» on uoouommHm NHunmoHMHdem uos cum muouumH uoHHaHm mnH>mn nasHoo m cHnuH3_msmozm A O.N n m.« m O.N m «.HN m N.N «H m N.N m O.N m w.« m «.ON a O.N N “NO HNV HNV ANV ARV umonexosn OHHS huOwadHauoa HHmH oHumHsu summon «weavan mwvom womavaHn mHon .Amhmvv oaHH ummH voumouu monHa uauHe :H O«H umHHaem 0 mo unmouon mm «unmounxo mmoH «mucouu onu aoum unmaw>oa «so ooHumuomnm mummonnNHquwm .H oHnma Table 2. Translocation of morningglory, 18 to 20 cm long field bindweed, 18 to 20 cm long hedge bindweed, 16 to 18 cm tall wild buckwheat, and 14 to 18 cm tall Canada thistle harvested and dissected into plant partsa 3 and 14 days after treatment expressed as percent of total 71 14c applied 14C-glyphosate in 12 to 14 mm tall tall Plant partb Weed species Time (days) Above Below Root Daughter (76) (74) (Z) (Z) Field bindweed 3 33 a 12 a 22 a 33 a 14 5 a 20 a 36 a 39 a Hedge bindweed 3 15 a 19 a 29 a 37 a 14 12 a 26 a 35 a 27 a Canada thistle 3 48 c 14 ab 22 ab 17 ab 14 25 ab 4 a 33 bc 38 c Tall morningglory 3 29 a 11 a 59 b 14 26 a 12 a 55 b Wild buckwheat 3 86 c 13 a l a 14 51 b 41 b 8 a aAbove (plant part above treated leaf), Below (plant part below treated leaf), Root (root), and Daughter (shoot opposite end of root from parent shoot). bMeans'within plant species with similar letters are not significantly different at the 5% level by Duncan's multiple range test. 72 for field bindweed, hedge bindweed, and tall morningglory. The radioautographs presented in Figures 1 through 5 support this observation. It is interesting to note that the greatest movement to mature leaves throughout the plant occurred in hedge bindweed (Figure 2) and the least in wild buckwheat (Figure 5). These results are consistent with observation of controls in the field. The transloca- tion pattern in all five species indicated phloem transport. Radio- autographs of longitudinal and cross sections of field bindweed root and stem confirm the localization of 14C label in the phloem (Figures 6 and 7). The TLC system employed in the metabolic studies afforded excellent separation of glyphosate and three potential metabolites. ENaluation of glyphosate metabolism in the various plant organs of field bindweed, Canada thistle, and tall morningglory showed the least parent 14C-glyphosate in the daughter plants for perennials 3 days after harvest and in the root of tall morningglory 1 day after harvest (Tables 3, 4, and 5). The percent parent compound increase with time. Since achieving 14C-glyphosate purity greater than 95 per- cent was difficult, the potential metabolite found in the metabolic studies may be no more than contaminants in the applied 14C-glyphosate. If so, the increase in the percent parent glyphosate in the daughter plants or roots with time indicates more rapid translocation of the aminomethylphosphonic acid than glyphosate. The results indicate that very little if any metabolism of glyphosate to aminomethylphosphonic acid occurred. Determination of the total 140 in all three species over the 30-day period indicated a marked decrease in 1"C for Canada thistle and tall morningglory (Tables 4 and 5). Combustion of the Figure 1. 73 Translocation of 14C-glyphosate in field bindweed 18 to 20 cm in length. The treated plant (A) and corresponding radioautograph (B) of field bindweed harvested 3 days after treatment. The treated plant (C) and corresponding radio- autograph (D) of field bindweed harvested 14 days after treatment. The treated leaf is marked with an arrow. 74 \ a‘ .fi ‘(x- ‘ 75 Figure 2. Translocation of 14C-glyphosate in hedge bindweed 18 to 20 cm in length. The treated plant (A) and corresponding radioautograph (B) of hedge bindweed harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (D) of hedge bindweed harvested 14 days after treatment. The treated leaf is marked with an arrow. 76 Figure 3. 77 Translocation of 14C-glyphosate in Canada thistle 14 to 18 cm tall. The treated plant (A) and corresponding . radioautograph (B) of Canada thistle harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (C) of Canada thistle harvested 14 days after treatment. The treated leaf is marked with an arrow. 78 Figure 4. 79 Translocation of 14C-glyphosate in tall morningglory 12 to 14 cm tall. The treated plant (A) and corresponding radioautograph (B) of tall morningglory harvested 3 days after treatment. The treated plant (C) and corresponding radioautograph (C) of tall morningglory harvested 14 days after treatment. The treated leaf is marked with an arrow. 80 Figure 5. 81 Translocation of 14C-glyphosate in wild buckwheat 16 to 18 cm tall. The treated plant (A) and corresponding radio- autograph (B) of wild buckwheat harvested 3 days after treatment. The treated plant (C) and corresponding radio- autograph (C) of wild buckwheat harvested 14 days after treatment. The treated leaf is marked with an arrow. 82 83 Figure 6. Location of 14C-glyphosate in field bindweed stems harvested 3 days after treatment. Treated plant (A) and corresponding radioautograph (B) of a stem longitudinal section. Treated plant (C) and corresponding radioautograph (C) of a stem cross section. 84 a" - -——- T 85 Figure 7. Location of 14C-glyphosate in field bindweed roots harvested 3 days after treatment. Treated plant (A) and corresponding radioautograph (B) of a roots longitudinal section. Treated plant (C) and corresponding radioautograph (C) of a stem cross section. 86 ' --.-- 87 .ummu owsmu OHmHuHOB m.smo=on an Hm>mH Nm mam um uamumwva NHuamUHMHdem now can muouuoH umHHaHm nuHB.AZmO Hmuou no Heuou mo unmouomv Houmamumm m aHsqu mucosa pm HNH«N m o m m m e we mm Housmamn m «NN« o O m « m N om Hm uoom no N«OHN m N m « m N m NN uaouom n NNNNNH m N o O m « N Na wmmH «mummua ON pm NN«N m N m N m HH on NN Hounwsmn em NNN« m N m m m N o NN uoom no «mm«« m N m H m « M Na uomumm a mHo-~ m H m o m H m Hm mmmH umumoua H m oNNm m 0H m oH a HH a mo pounwsmn m NNO« m N m N m N mo.NN uoom no NNNN« m N m N m « m Hm usmumm o mowoNN m H a H m s we so HmmH assuage m can H395 CO NE H5 33 maHmooumm moHoNHu «How UHaonmmonn mummonONHO Ammmvv O«H IHNnumaodHa< muumm uanm unmaumouu Houmm oaHH so a u m o o m a .. m HuAMMIu H« Ame e um O«H uumm unMHO some OH,O«H Hmuou mo unmouom mm vommouexo ucoaumwuu Houmm mmmv ON «no .N .N woumm>ume voo3mcHn wHon numsoH 50 NH 0» OH aH cosmoneNHwIO mo smHHOOMuoa mnu so mdmwuo uane «so osHu mo assume any .N mHan «H 88 .uoou owaou oHnHuHaa m.oooo=O Nn Ho>oH Nn onu no uoouommHv NHudoUHMHoNHo uoa muo ououuoH uoHHaHo nuHa Axum Houou no HouOu mo udmouomv Houoaouon o aHnuH3 mooozo 1 1 1‘ ‘11 4 ‘l‘ 4 J u NNNNN a N m N m N mm mm Hauewsma ono NN«NH o N o N o N nN «m uoom vIn NNNNH o N o N o N NIo Hm unouom N NNONN o N o « o « mic NN mooH «ouooua ON no «NNN o N o N n OH O «N Hounwson mu omsNH m N m N m N mm mm seem a NmnmN m H m H a N no ma Samoan o «NNN«H o H o « no « wIN NN mooH vouooua N o NNNN no N no N no N o mN nounwoon no NNNN m N m a m N N.» Na scam no NN«N o « o N o N NIo Hm uaouom m NNHNNN o «.O o «.O o N n NN mooH vouooua N Name Hmuoav HNV HNV HNV HNV oOHooouom oaHoNHO «Hoo oHoonOoonm ouooonmNHO thovv O«H . IHNnuoaoaHa< ouuon uaon unoauoouu Houmo oaHH HHO “3 Hum mu 0 Mums m H pH He HH a use anon uooHn nooo nH O«H Houou mo unmouoa mo Noooounxo unoauoouu Houmo oNom ON «no .N .N «ouoo>uon oHuoHnu oooooo nuNnoH Bo NH ou OH nH ouooonmNHNIO«H mo amHHonouoa onu no oaowuo unoHn Ono oaHu mo uoowmo one .« oHnoH 89 .uoou oNdou oHdHqua o.dooddO Nn Ho>oH Nm onu uo udouommHv NHudoonHdNHo uod odo odouuoH uoHHaHo nuHa.Asz Houou Ho Houou No udoouodv Houoaouon o dHnuH3.odoozo n «NNN o N o N o « «0 NN uoom o HHNN o N o N o « om Hm onoN no ONNN o m o N o « «a «N , o>on< o NN«NN o N o H o « mo Nm momH «ouooua HN n NNN« o N o N o « «u.mN uoom o «m«N o N o N o OH on «N 30HoN n m««« o « o N o « «0 NN o>on< N NNNN«H o « o N o « «o «N mooH «ouooua N no NHN« o « o « o HH n NN doom o «NNH o N o H o N qu NN . 30Hom o «NON o H o H o N H mm o>on< o NNNNNN o N o N o N «0 NN mooH «ouooua H can H323 HNV ab GO GO odeoouoN odHoNHO «Hoo oHdonmoonm ouooondNHO Homovv O«H IHNnuoEOstd muuod udon udoauoouu woumo QEHH odOHudnHuuoHv ouHHonouoa o «H uuod udoHd nooo dH 0 H Houou mo udouuom mo «monoudxo udoauoouu Houmo oNoN HN «do..N .H «oumo>uon NuoHNwdeuod HHou.nuNdoH do NH on OH dH ouooonmNHNIo«H mo aoHHonouoa onu do odowuo udoHd «do odHu mo noomwo onH .m oHnoH 90 extraction precipitate or insoluble residue indicated negligible accumulation of 14C in that fraction. In search of an explanation, excised field bindweed and tall morningglory leaves received foliar applications of 14C-glyphosate and the loss of 14C was monitored. No loss was evident for 2 days (Table 6). However, from 3 to 25 days after treatment the leaves of field bindweed and tall morningglory lost 47 and 43 percent of the 14C applied, respectively. Since these were excised leaves, absorption and translocation could not account for the loss. The rate of loss was similar to that observed in soil for the conversion of 14C-glyphosate to 14002 (9, ll, 12, 14). The action of microbial organism on the leaf may account for this loss, however, metabolism of l4C-glyphosate to a volatile 14C- labeled metabolite, perhaps but not necessarily 002, by the excised leaves cannot be discounted. The loss of 140 from the excised leaves of the two species was very similar (Table 6), whereas the loss of 14C from the treated leaves on the intact plant was more pronounced for tall morningglory and Canada thistle than for field bindweed (Tables 3, 4, and 5). Differences in leaf area treated or differences in metabolism may account for the observed differences among species in the loss of 14C. In conclusion, differences in absorption and translocation appear associated with variability in glyphosate efficacy. Furthermore, greater basipetal translocation could be achieved if translocation were allowed to proceed for more than 3 days in Canada thistle and wild buckwheat. In Canada thistle control, this could be of significance in tillage operations. 91 Table 6. The loss of 14C-glyphosate from treated leaves of field bindweed and tall morningglory detached from plants at time of treatment Total 14C a Time Field bindweed Tall morningglory (DPM/treated leaf) (DPM/treated leaf) 0 hr 570612 de 571304 de 1 hr 585711 e 584650 e 6 hr 581667 de 580659 de 12 hr 586772 de 586634 de 1 day 559201 d 559180 d 2 days 617703 de 617669 de 3 days 485219 c 487274 c 11 days 417899 b 416308 b 18 days 395615 b 393676 b 25 days 323113 a 329598 a aMeans, within a column, followed by the same letter are not signifi- cantly different at the 5% level by Duncan's multiple range test. 10. 11. 12. 13. 14. 92 Literature Cited Baird, D. D., N. J. Shaulis, and C. G. Waywell. 1974. Glyphosate for herbaceous perennial weed control in northeastern apple orchards and vineyards. Proc. N. E. Weed Sci. Soc. 28:205-212. Baird, D. D., R. P. Upchurch, W. B. Homesley, and J. E. Franz. 1971. Introduction of a new broad spectrum postemergence herbicide class with utility for herbaceous perennial weed contol. Proc. North Cent. Weed Contr. Conf. 26:64-68. Behrens, R. and M. Elakkad. 1972. Quackgrass control with glyphosate. Proc. North Centr. Weed Contr. Conf. 27:54. Claus, J. S. and R. Behrens. Gluphosate translocation and quack- grass rhizome bud kill. Weed Science. 24:149-452. Davison, J. C. 1972. The response of 21 perennial weed species to glyphosate. Proc. Brit. Weed Contr. Conf. 1:11-16. Hemphill, D. D., R. L. Baumgartner, and A. D. Hibbard. 1975. Control of weeds in orchards and vineyards with glyphosate. Weed Sci. Soc. Amer. Abstr. p. 14. Putnam, A. R. 1976. Fate of glyphosate in deciduous fruit trees. Weed Sci. 24:425-430. Putnam, A. R., A. P. Love, and G. Pagano. 1974. Response of deciduous fruit trees and several orchard weeds to glyphosate. Weed Sci. Soc. Amer. Abstr. p. 116. Rieck, C. W., T. H. wright, and T. R. Harger. 1974. Fate of glyphosate in soil. weed Sci. Soc. Amer. Abstr. p. 119. Rueppel, M. L., J. T. Marvel, and B. B. Brightwell. 1975. The metabolism and dissipation of N-phosphonomethyl glycine in soil and water. Amer. Chem. Soc. Div. Pesticide Chem. Abstr. p. 8. Rueppel, M. L., J. T. Marvel, and L. A. Suba. 1975. The metabo- lism of N-phosphonomethylglycine in corn, cotton, soybeans, and wheat. Sprankle, P., W. F. Meggitt, and D. Penner. 1972. Adsorption, mobility and microbial degradation of glyphosate in the soil. Weed Sci. 23:229-234. Sprankle, P., W. F. Meggitt, and D. Penner. 1972. Adsorption, action and translocation of glyphosate. Weed Sci. 23:235-240. Sprankle, P., W. F. Meggitt, and D. Penner. 1974. Adsorption and metabolism of glyphosate in the soil. Weed Sci. Soc. Amer. Abstr. p. 119. 15. 16. 17. 18. 93 Sprankle, P., C. L. Sandberg, W. F. Meggitt, and D. Penner. Separation of glyphosate and several possible metabolites by thin- layer chromatography. Weed Sci. (Submitted). Stoller, E. W., and L. M. Wax. 1972. Response of yellow nutsedge to bentazon, glyphosate, and MBR 8251. Proc. North Centr. Weed Contr. Conf. 27:55. wang, C. H., and D. L. Willis. 1965. Radiotracer methodology in biological science. Prentice Hall, Inc., Englewood, N.J. p. 363. Wyrill, J. B., III, and O. C. Burnside. 1976. Adsorption, translocation, and metabolism of 2, 4-D and glyphosate in common mildweed and hemp dogbane. Weed Sci. 24:557-566. CHAPTER 5 SUMMARY AND CONCLUSIONS Studies were initiated in the field, greenhouse, and laboratory to evaluate the activity of glyphosate on field bindweed and to determine herbicide and management practices which provide effective control of field bindweed, to establish the effects of diluent volume and calcium on glyphosate phytotoxicity, and to study absorption, translocation, and metabolism of glyphosate. In the field, foliar application of glyphosate at rates of 1.12 kg/ha and greater, treated from.flower bud stage in the spring to late fall, provided effective field bindweed control. A single application of glyphosate provided satisfactory control for two growing seasons, after which additional glyphosate treatments were required at similar intervals to establish continual control. Glyphosate did not completely kill roots and rhizomes of field bindweed, but, growth of these under- ground organs was inhibited for 2 or 3 seasons. Tillage prior to appli- cation of glyphosate reduced the control obtained. For example, tillage in the fall and/or spring rendered June treatments inactive. Tillage after treatment increased control of glyphosate only when the control obtained from glyphosate was marginal. I Glyphosate phytotoxicity was decreased when diluent volumes were increased above 190 L/ha because of runoff and inactivation by calcium 94 95 in the water. Runoff,calcium,and their interaction, all contributed to decreased performance by themselves as well as interacting. As an example, as diluent folume increased the concentration of calcium per unit of glyphosate increased. Even a small amount of calcium decreased effectiveness at high diluent volumes, however, at low volumes 190 L/ha and lower, calcium did not become a factor except at exaggerated levels. Absorbance of chemicals is usually the evaluation of the amount of the applied material which enters the treated leaf. In perennial weed studies it is important to determine how much material actually leaves the treated leaf and is translocated in the plant. Only a small fraction of the applied glyphosate was absorbed and translocated, 3 to 21 percent depending