(:) COPYRIGHT BY RUNGSIT SUNANKETNIKOM 1978 YELLOW NUTSEDGE (CYPERUS ESCULENTUS L.) CONTROL WITH BENTAZON (S-ISOPROPYL-lfl-Z , 1 , 3- BENZOTHIADIAZIN- (4) l3fl- ONE 2,2-DIOXIDB) AND GLYPHOSATE (N;(PHOSPHONOMETHYL)CLYGINE) BY Rungsit Suwanketnikom 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 YELLOW NUTSEDGE (CYPERUS ESCULENTUS L.) CONTROL WITH BENTAZON (IS-ISOPROPYL-lfl-Z , 1 , 3- BENZOTHIADIAZIN-4- (35) - ONE 2,2-DIOXIDE) AND GLYPHOSATE (N-(PHOSPHONOMETHYL)GLYCINE) BY Rungsit Suwanketnikom Postemergence application of bentazon (3-isopropyl-lH-2,l,3- benzothiadiazine-4-(SH)-one 2,2-dioxide) to yellow nutsedge (Cyperus esculentus L.) grown in the greenhouse provided greatest control when applied at rate 2.2 kg/ha to 7.6 cm tall plant and resulted in death of parent tuber. A single 2.2 kg/ha application was more effective than a single 1.1 kg/ha application. Bentazon was less effective on taller . plants, control was less than 50% with single application of 2.2 kg/ha application to plantslyldicm tall or taller. Split applications of bentazon enhanced control, a time lapse between split applications of 5 days provided greater control than 10 or 20 days if the initial appli- cation was l.l kg/ha and the plants were 30.5 cm tall or less. Under field conditions, split applications of bentazon also provided greater control than a single application when applied to plants 5 to 7.6 and 10 to 15.2 cm tall. A time lapse between first and second applications from 10 to 20 days did not effect yellow nutsedge control. Applications of bentazon to 20 or 30.5 cm tall yellow nutsedge did not provide control Rungsit Suwanketnikom and resulted in soybean (Glycine max L.) yield loss. Single postemergence applications of glyphosate (N;(phosphonomethyl) glycine) controlled shoots of 7.6 cm tall yellow nutsedge plants but not taller plants, and the parent tubers still lived. Further greenhouse and growth chamber studies indicated that a higher light intensity (48.4 klux) increased the activity of glyphosate. In contrast, bentazon caused more injury to yellow nutsedge under low light intensity (16.1 klux). Bentazon and glyphosate were more effective under high soil moisture (field capacity) than under low soil moisture condi- tions. Bentazon caused more injury to 7.6 cm tall plants at 15 C than 35 C. When the plants were 30.5 cm tall bentazon caused greatest injury at 25 C. Glyphosate controlled 7.6 cm tall plants at 15, 25, and 35 C. But when the plants were 30.5 cm tall, glyphosate controlled only plants grown at 25 and 35 C. Additives to increase bentazon and glyphosate activity were evalu- ated in the greenhouse. Ammonium phosphate, ammonium chloride, ammonium sulfate, and ammonium thiocyanate in combination with bentazon signifi- cantly increased bentazon injury to yellow nutsedge plants. Ethephon (Z-chloroethylphosphonic acid), 2,4-0 (2,4-dichlorophenoxy)acetic acid), urea and ammonium salts in combination with glyphosate also increased - yellow nutsedge injury primarily by reducing the stand density. In laboratory studies more 14C-bentazon was absorbed and translo- cated by 7.6 cm tall plants than those 15.2 cm tall. 14C-bentazon moved acropetally and basipetally and translocated down into tubers of 7.6 and 15.2 cm tall plants. Split applications of bentazon and addition of ammonium sulfate increased 14C-bentazon absorption and translocation in 15.2 cm tall plants. Yellow nutsedge grown in EPTC (Sfethyl-dipropyl Rungsit Suwanketnikom thiocarbamate) treated sand culture and in low soil moisture conditions absorbed less 14C-bentazon. More 14C-glyphosate was absorbed by 15.2 cm tall than 7.6 cm tall plants. However, translocation was greater in 7.6 cm tall plants than 15.2 cm tall plants 5 days after treatment. No 14C-glyphosate was trans- located to tubers. Ethephon and ammonium sulfate increased 14C-glyphosate absorption and translocation by 15.2 cm tall plants but only ethephon increased basipetal movement of 14C-glyphosate to the tubers. Less l4C- glyphosate was absorbed by plants grown under low light intensity than by plants grown under high light intensity. Most of the 14C found in the treated leaf, other leaves, roots, rhizomes and parent tubers was parent bentazon. The metabolism in various plant parts was similar with up to nine 14C-metabolites separated. The percent of 14C remaining as parent or non-metabolized bentazon did not differ in 7.6, 15.2 cm tall plants, or 15.2 cm tall plants treated with ammonium sulfate. ACKNOWLEDGMENTS The author would like to express his sincere appreciation to Dr. Donald Penner for his guidance and patience at all times during this study and in the preparation of this dissertation. The assistance of Dr. W. F. Meggitt, Dr. J. A. Cornelius, Robert Bond and Ronald Sterns for field research is gratefully acknowledged. Gratitude is expressed to Drs. R. W. Chase, W. F. Meggitt, A. R. Putnam, and M. Zabik for their service as guidance committee members. Appreciation is extended to Kasetsart University for their financial support during this study. The author would also like to thank Dr. Suranant Subhadrabandhu for his assistance in making the opportunity at Michigan State University possible. Finally, special appreciation is extended to my wife, Suwatana, whose diligence and patience has contributed tremendously to my success. ii TABLE OF CONTENTS Page LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . v LIST OF FIGURES . . . . . . . . . . . . . . .'. . . . . . . . . . .viii INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 CHAPTER 1: LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . 3 Biology of Yellow Nutsedge . . . . . . . . . . . . . Taxonomy. . . . . . . . . . . . . . . . . . . . . . . Anatomy and Morphology. . . . . . . . . . . . . . . . . Propagation and Tuber Dormancy . . . . . . . . . . Growth and Development . . . . . . . . . . . Distribution and Ecotypes . Agricultural Importance of Yellow Nutsedge Yellow Nutsedge Control with Herbicides . . . . . . . . . Behavior of Bentazon in Plant and Soil . . . . . . . . . . . . ll Behavior of Glyphosate in Plant and Soil . . . . . . . . . . . 15 The Influence of Ammonium Salts on Herbicide Phytotoxicity . . 17 The Influence of Bthephon on Herbicide Phytotoxicity . . . . . 18 KOCDVU'IUTOJMM CHAPTER 2: YELLOW NUTSEDGE (CYPERUS ESCULENTUS) CONTROL WITH BENTAZON AND GLYPHOSATE . . . . . . . . . . . . . . . . 19 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 20 Materials and Methods . . . . . . . . . . . . . . . . . . . . . 21 Results and Discussion . . . . . . . . . . . . . . . . . . . . 22 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 26 CHAPTER 3: INFLUENCE OF THE ENVIRONMENT ON YELLOW NUTSEDGE (CYPERUS ESCULENTUS) CONTROL WITH BENTAZON AND GLYPHOSATE . . . . . . . . . . . . . . . . . . . . . . . 33 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 34 Materials and Methods . . . . . . . . . . . . . . . . . . . . . 34 Results and Discussion . . . . . . . . . . . . . . . . . . . . 36 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 39 iii Page CHAPTER 4: ADDITIVES TO INCREASE BENTAZON AND GLYPHOSATE ACTIVITY ON YELLOW NUTSEDGE (CYPERUS ESCULENTUS) . . . . 45 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 46 Materials and Methods . . . . . . . . . . . . . . . . . . . . . 47 Results and Discussion . . . . . . . . . . . . . . . . . . . . 47 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 51 CHAPTER 5: INFLUENCE OF STAGE OF GROWTH ENVIRONMENTAL FACTORS AND ADDITIVES ON 1"c-EENTAZON AND 1“(z-GLYPHOSATE ABSORPTION AND TRANSLOCATION BY YELLOW NUTSEDGE (CYPERUS ESCULENTUS) . . . . . . . . . . . . . . . . . . 59 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 60 Materials and Methods . . . . . . . . . . . . . . . . . . . . . 61 Results and Discussion . . . . . . . . . . . . . . . . . . . . 63 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 68 CHAPTER 6: METABOLISM OF ll'C-BENTAZON BY YELLOW NUTSEDGE (CYPERUS ESCULENTUS) . . . . . . . . . . . . . . . . . . 82 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 83 Materials and Methods . . . . . . . . . . . . . . . . . . . . . 84 Results and Discussion . . . . . . . . . . . . . . . . . . . . 85 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 89 CHAPTER 7: SUMMARY AND CONCLUSION . . . . . . . . . . . . . . . . . 99 LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . 102 iv Table LIST OF TABLES Chapter 2 1. Influence of plant height and rate of bentazon application on yellow nutsedge growth in the greenhouse 40 days after application . . . . . . . . . . . . . . Split postemergence application of bentazon to yellow nutsedge grown in the greenhouse with an initial applica- cation rate of 1.1 kg/ha and second application rate of 1.1 or 2.2 kg/ha . . . . . . . . . . . . . . . . . Split postemergence application of bentaton to yellow nutsedge grown in the greenhouse with an initial applica- tion rate of 2.2 kg/ha and second application rate of 1.1 or 2.2 kg/ha . . . . . . . . . . . . . . . . Influence of plant height, rate and split application of bentazon on yellow nutsedge control and soybean yield in the field in 1975 and 1976 . . . . . Influence of plant height and rate of glyphosate applica- tion on yellow nutsedge grown in the greenhouse 30 days after application . . . . . . . . . . . . . . . . . . . . . . Chapter 3 1. The effect of light intensity on bentazon and glyphosate activity on yellow nutsedge 15.2 cm tall measured 30 days following treatment . . . . . . . . . . . . . . . The effect of soil moisture on bentazon and glyphosate activity on yellow nutsedge 15.2 cm tall measured 30 days following treatment . The effect of temperature on bentazon activity on yellow nutsedge 7.6 and 30.5 cm tall measured 30 days following treatment . . . . . . . . . . . . . . . . . . . . . . . . The effect of temperature on glyphosate activity on yellow nutsedge 7.6 and 30.5 cm tall measured 30 days following treatment . . . . . . . . . . . . . . . . . . . . . . . Page 28 29 3O 31 32 41 42 43 44 Table Page Chapter 4 1. Control of yellow nutsedge 15 cm tall with postemergence application of bentazon plus, 2,4-D, ethephon, or urea . . . 53 2. Control of yellow nutsedge 15 cm tall with postemergence application of bentazon plus various ammonium salts . . . . . 54 3. The effect of pH on control of yellow nutsedge 15 cm tall with bentazon . . . . . . . . . . . . . . . . . . . . . . . . 55 4. Control of yellow nutsedge 15 cm tall with postemergence application of glyphosate plus 2,4-D, ethephon, or urea . . . 56 5. Control of yellow nutsedge 15 cm tall with postemergence application of glyphosate plus various ammonium salts . . . . 57 6. The effect of pH on control of yellow nutsedge 15 cm tall with glyphosate . . . . . . . . . . . . . . . . . . . . . . . 58 Chapter 5 1. The effect of time, stage of plant growth, additives and soil moisture on foliar absorption of 1“C-bentazon on yellow nutsedge . . . . . . . . . . . . . . . . . . . . . . . 78 2. The effect of time, stage of plant growth, additives and soil moisture condition on l"C-bentazon translocation in yellow nutsedge expressed as percentage of total translocated and amount of ll‘C-bentazon per plant dry weight . . . . . . . 79 3. The effect of time, stage of plant growth, additives, and light intensity condition on foliar absorption of 1"C- glyphosate on yellow nutsedge . . . . . . . . . . . . . . . . 80 4. The effect of time, stage of plant growth, additives and light intensity condition on l‘C-glyphosate translocation in yellow nutsedge expressed as percentage of total trans- located and amount of 1"C-glyphosate per plant dry weight . . 81 Chapter 6 1. Comparison of total 1"C found in various parts of yellow nutsedge plants 7.6 cm tall harvested 1, 5, and 10 days after “C-bentazon treatment 91 2. Metabolism of 1“C-bentazon in various parts of yellow nutsedge plants 7.6 cm tall 1, 5, and 10 days after treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 92 vi Table Page Chapter 6 (continued) 3. Metabolites of 1"C-bentazon and corresponding Rf values obtained from various plant parts of yellow nutsedge 7.6 cm tall 1, 5, and 10 days after treatment . . . . . . . . . . 93 4. Comparison of foliar absorption of l"C-bentazon and per- centage of unmetabolized bentazon in the treated leaves of yellow nutsedge l, 5, and 10 days after various treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 94 5. Comparison of total 1"C found in above and below treated area of yellow nutsedge leaves harvested 1, 5, and 10 days after various treatment of 1"C—bentazon . . . . . . . . 95 6. Metabolism of ll'C-bentazon in above and below treated area of yellow nutsedge leaves 1, 5, and 10 days after various treatment . . . . . . . . . . . . . . . . . . . . . . 96 7. Metabolites of 1"C-bentazon and corresponding Rf values obtained from above and below treated areas of yellow nutsedge leaves, 1, 5, and 10 days after various treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 97 vii Figure Chapter 5 l. 2. plants above, (A) 1 3. 5 days after foliar application. autographs below (C-D) 4. Translocation of ll'C-gl LIST OF FIGURES Translocation of l"C-bentazon in yellow nutsedge 7.6 cm tall. Plants harvested (A) 1 day, (B) 5 days, and (C) 10 days after foliar application. Treated plants above (A-C) and corresponding radioautographs below (D-F) Translocation of ll'C-bentazon in yellow nutsedge 15.2 cm tall harvested 5 da 5 after foliar application. Treated C-bentazon applied alone, (B) 1"C- bentazon applied in combination with ammonium sulfate, (C) split applicationsl“C-bentazon applied 5 days after application of 1.1 kg/ha of bentazon, and (D) 1 C-bentazon applied when plants were grown in low soil moisture condi- tions. Corresponding radioautograph below (E-H) Translocation of ll’C-glyphosate in yellow nutsedge 7.6 cm tall. Treated plants above harvested (A) 1 day and (B) 15.2 cm tall receiving graphs are (J-L) I? Corresponding radio- hosate in yellow nutsedge plants C-glyphosate applied (A) alone, (8) in combination with ethephon, and (C) in combination with ammonium sulfate 1 day after foliar application. Corresponding radioautographs are (D-E). Plants receiving 1"C-glyphosate applied (G) alone, (H) in combination with ethephon, and (I) in combination with ammonium sulfate 5 days after foliar application. viii Corresponding radioauto- Page 71 73 75 77 INTRODUCTION Most preemergence herbicides used for yellow nutsedge (Cyperus esculentus L.) control killed only the sprouting buds but not the tubers (101,113,119), Tubers contain several buds in various stages of dormancy. It is difficult to kill all the buds on a tuber with a single herbicide application (113). When ever the herbicide concentration in soil de- creased to less than optimum for yellow nutsedge control, the plants resumed growth. Bentazon (3-isopr0pyl-IH;Z,I,3-benzothiadiazin-(4)3H70ne 2,2-dioxide), a selective postemergence herbicide for broadleaf weed control in corn (Zea mays L.) (62), soybean (Glycine max L.) (56,66,71,101,114), rice (Oryza sativa L.) (3), navy bean (Phaseolus vulgaris L.) (3) and Kentucky bluegrass (Poa pratensis L.) (3,50,63) has shown potential for yellow nutsedge control (101,102,103). Glyphosate (N;(phosphonomethyl)glycine), a non selective postemerg- ence herbicide for annual, perennial, grass and broadleaf weed control (7), has also been reported to control yellow nutsedge (20,101). The purpose of this research was to determine: (1) the Optimum stage of yellow nutsedge growth, bentazon and glyphosate rate, and time lapse between split applications of bentazon for yellow nutsedge control; (2) the effect of bentazon and glyphosate on tuber viability and bentazon on soybean yield were also considered; (3) the influence of light inten- sity, soil moisture, and temperature on yellow nutsedge control with 1 2 with bentazon and glyphosate; (4) potential of additives to increase the activity of bentazon and glyphosate on yellow nutsedge; (5) the influence of stage of plant growth, split applicationscflfherbicide, additives and environmental conditions on absorption and translocation of 14C-bentazon and 14C-glyphosate on yellow nutsedge; and (6) the nature of bentazon metabolism in yellow nutsedge. CHAPTER 1 LITERATURE REVIEW Biology of Yellow Nutsedge Taxonomy Yellow nutsedge (Cyperus esculentus L.), a perennial herb, has been classified in the family Cyperaceae (24). Culms (rachis) are triangular, stem like, erect above ground, and terminated by an inflorescence (126). Leaves are three ranked, pale green 4 to 6 mm wide with a prominent mid- vein about as long as or longer than the culm. The inflorescence is subtended by unequal leaf like bracts varying from S to 25 cm long (49). Spikelets are golden brown, 0.5 to 3 cm long and 1.5 to 3 mm wide, and pinnately arranged along an elongate axis (126). There are three stamens and three cleft styles in each flower (49). The achenes are yellowish brown, three angled, and 1.2 and 1.5 mm long. They are covered by a thin ablong, obtuse-shaped scale (126). The root system is fibrous (25). Rhizomes are covered by cladophylls at nodes and long internodes (51). Tubers are 1 to 2 cm long (25). Anatomy and Morphology Wills (126) reported that leaves grow out from the bulb in an in- folded triangular fascicle. Fascicle development on the bulb begins at the outer-most leaf, progresses inward, and terminates with a seed-bearing 4 rachis (126). The upper leaf surface is composed of large epidermal cells covered by waxy cutin and no stomata. The lower leaf surface is composed of smaller epidermal cells and cover less cutin than the upper leaf surface (126). The vascular bundles are surrounded by chloren- chymatous cells (126) Similar to those of purple nutsedge (C. rotundus L.) (124). Black gt_al, (17) categorized purple nutsedge as a C4 plant, yellow nutsedge may also be categorized a C4 plant (126). There are vacuolated cells which are supported by a fiber bundle above and below vascular bundle cells (126). Rhizomes develop from parent tuber or basal bulbs (51). Cross sec- tions of rhizome reveal an epidermis, a cortex, and an endodermis sur- rounding a vascular cylinder. The vascular cylinder have the xylem out- side the phloem. There is an apical meristem at the rhizome apex covered by sharply pointed scale-leaves (cladophylls) (126). Tuber formation occurs at the rhizome apex in the meristematic region. The internodes cease to elongate and the leaf primodia remain dormant during tuber maturity (51). The vascular bundles in tubers are the same as in rhizomes and are continuous from the rhizome through the tubers to buds and roots (16). The basal bulb is formed from the rhizomes apex in the meristematic region the same as tubers except the leaf primodia do not become dormant and subsequent shoots elongation occurred (51). Roots can be formed from the endodermis of tubers, bulbs, or rhizomes. Cross-sections of roots reveal xylem vessels surrounded by phloem vessels. The vascular cylinder is surrounded by a pericycle which is surrounded by endodermal cells. The endodermis is surrounded by cortex and epidermis (126). Propagation and Tuber Dormancy Yellow nutsedge is propagated by both seeds and tubers (12,13,54, 112). A simple seedling develops into a stand of plants that can produce a yield of 90,000 seeds with germination of 51% (47). However, under field conditions yellow nutsedge seeds germinate only 1 to 32% (12). Seeds germinate in the zone very close to the soil surface and do not germinate at 3.3 cm or deeper (12). Tubers are the principal way yellow nutsedge spreads in agricultural land (13). One tuber may produce 1900 plants and 6,900 tubers in 1.6 square meter in one year (112). Most tubers were found in the zone up to 15 cm below soil surface (112) and most of them sprouted from this zone (26,98). However, they can sprout from as much as 30 cm below the soil surface (112). The percent of Sprouting depends on soil type with low sprouting percentages found in compacted soil (26). In Illinois (98), under field conditions, tubers remained viable for a period of up to 22 months, however, Bell gt_al, (13) reported the percent of sprouting was still high after 3 years of storage at room temperatures or under refrigeration. Yellow nutsedge tubers are sensitive to cold temperature (97,110) and little sprouting occurs when buried in the field at 2.5 and 5.1 cm depth (98). Tuber dormancy occurs during the late summer and early fall. Sprouting was highest during the winter and spring (109). Growth Development Tubers are the source of shoots, rhizomes, root and basal bulbs (51, 96). During sprouting, over 60% of the tuber dry weight, carbohydrate, oil, starch and protein were consumed (96). If sprouting is disturbed 6 or arrested new buds can sprout (111) but then less than 10% of the con- stituents were utilized during subsequent sprouting (96). There are five to seven buds formed, per tuber, one per node. The oldest bud is the largest and located at the basipetal end of the tuber. The smallest bud is the youngest and located at the apical end of the tuber. Buds break dormancy in acropetal order starting with the oldest bud (16). One or more rhizomes are formed from the newly sprouting bud. Each rhizome develops a basal bulb (51,96). The length of rhizome between the tuber and basal bulb may be several meters or Shorter and it appears that the basal bulb develops from the tuber without a rhizome (51). Basal bulbs are the basic site of leaf shoot and subterranean growth (51). The apical growth of basal bulbs produces the leafly plant and inflorescence. The new rhizomes also develop from the basal bulb and may deveIOp into new tubers or secondary basal bulbs. If the plant forms secondary and terti- ary basal bulbs, it will become a complex system (51). Growth of yellow nutsedge was tremendously effected by the photo- period, and increased photoperiod from 14 to 24 hrs., increased vegetative growth. New photosynthic leaves differentiate every 4.5 to 5 days, and exhibited sigmoid pattern of growth for 24 to 40 days (51). The rate of basal bulb formation from rhizome tips was maximum at 16 hours (51) and the rate of tuber formation maximum at a 8 to 12 hour photoperiod (37, 51). Delayed tuber formation occurred under the longest photoperiod (37, 51). Flowering occurred with a 12 to 14 hour photoperiod. Active vege- tative growth was competitive with tuberization and flowering was compe- titive with both shoot formation and tuberization (51). Not only long photoperiods, but high levels of nitrogen in the soil, 7 and gibberellic acid also inhibit tuberization (14,15,37). High tempera- tures and low level of nitrogen favored tuberization (37). Shoot forma- tion was promoted and carbohydrate level in plants decreased when soil nitrogen levels were high, photOperiod long and temperatures high (37). Triiodobenzoic or naphthylphthalanic acid also accelerated transformation of rhizomes to shoots (14). Distribution and Ecotypes Yellow nutsedge is distributed from the equator to Alaska and even found in eastern and southern Africa (49). It can grow in all soil types, including black peat soil, and grows well at a pH of S to 7 (49). General- ly, it is found in poorly drained soils (49,117). However, it is very susceptible to low light intensity or shading (49,61). There are different ecotypes of yellow nutsedge with different mor- phological characteristics such as tuber size and leaf size in different parts of the United States (21,70). Hauser (42) suggested that variable susceptibility of yellow nutsedge to atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-§ftriazine) and 2,4-0 ((2,4-dichlorophenoxy)acetic acid) in different geographical areas may be explained by the presence of different yellow nutsedge varieties. Recently Casta and Appleby (27) categorized yellow nutsedge into two different varieties, C. esculentus L. var. esculentus and C. esculentus var. leptostachyus. Var. esculentus was less susceptible to preplant application of atrazine and metribuzin (4-amino—6-tertfbutyl-3-(methyl- thio)-a§;triazine-5(4H)one) but more susceptible to postemergence 2,4-D than leptostachyus (27,133). Yip and Sweet (132) described the charac- teristic of these two varieties. Var. esculentus has short Spikelets 8 (0.5—l cm) and produces small sized but many tubers and secondary shoots are produced 1-2 cm away from the primary shoot, whereas va. leptostachyus has a long spikelet (1.5-3.5 cm), produced fewer, but large sized tubers and secondary shoots are produced 5-14 cm away from the primary shoot. Stoller and Weber (100) reported that yellow nutsedge "I" the Illinois ecotype and yellow nutsedge "G" the Georgia ecotype contain very differ- ent amounts of starch and lipids after exposure to 2 C for 6 weeks. Yellow nutsedge "I" had a higher ratio of unsaturated to saturated fatty acids, higher triglycerides and polar lipids than yellow nutsedge "G". Starch and lipid contents increased significantly in yellow nutsedge "I" but did not change in yellow nutsedge "G". Agricultural Importance of Yellow Nutsedge Yellow nutsedge has been ranked as one of the most serious weed problems in the United States (51,117). The areas infested by this weed have increased in the past decide (13,49,67). Using herbicides for annual weed control and reduced tillage may have increased yellow nutsedge infestation in crop land (42). Yellow nutsedge not only reduces yields and increases crop produc- tion cost, but reduces crop quality as well (13). The rhizomes of yellow nutsedge grow into and through potato (Solanum tuburosum L.) tubers causing them to be graded as culls. Clumps of yellow nutsedge went through lima beans (Phaseolus linensis L.) and caused viners to break down (13). Tubers of yellow nutsedge could be mixed with shell beans (13). In cotton (Gossypium hirsutum L.) fields, yellow nutsedge also de- layed cotton maturity (60). 9 Holm §£_al, (49) reported that yellow nutsedge is a weed on all con- tinents. It is a serious weed of sugar cane in Hawaii, Peru, South Agrica, and Swaziland; of corn in Angola, South Africa, Tanzania, and United States; of cotton in Mozambique, Rhodesia, and United States; of soybeans in Canada, South Africa, and United States; of potatoes in Canada, South Africa, and United States; and of vegetable in Mozambique and United States. Yellow Nutsedge Control with Herbicides Herbicides have played an important role in yellow nutsedge control but a combination of herbicides and tillage is often needed for maximum yellow nutsedge control (121). All herbicides discussed below are cur- rently used for yellow nutsedge control. Alachlor (2-chloro-2,6—diethyl-N;(methoxymethyl)acetanilide) is a selective herbicide that can be used for yellow nutsedge control in corns (Zea mays L.) (62), soybeans (Glycine max (L.) Merr.) (4,84,119), and cottons (57,58,59). Preplanting incorporation of alachlor provided greater control than preemergence applications when rainfall was limited (4,5). Metolachlor (2-chloro—N;(2-ethyl-6-methylphenyl)-N;(2-methoxy-l- methylethyl)acetamide) is chemically similar to alachlor and can also be used to control yellow nutsedge in corn (30,48), soybeans (30), peanuts (Arachis hypogaea L.) and potatoes (48). Metolachlor provided more effec- tive (29) and longer season (48) control of yellow nutsedge than alachlor because it was more persistent in the soil than other acetanilide herbi- cides (29). 10 EPTC (Sfethyl diprophylthiocarbamate) one of the oldest herbicides, is also used for yellow nutsedge control in corn (13), cotton (43), and soybeans (119). Occasionally EPTC causes corn injury, however, a protec- tant or antidote, R-25788 (N,Nfdiallyl-2,2-dichloroacetamide) has been used in combination with EPTC. EPTC plus antidote provided yellow nut- sedge control and less corn injury than EPTC alone (62,121). Butylate (Sfethyl diisobutylthiocarbamate) is from the same chemical group as EPTC but appeared less effective than EPTC for yellow nutsedge control. It shows less corn injury than EPTC (43,62,84). Vernolate(§;propyl dipropylthiocarbamate) is one of the most effec- tive herbicides for yellow nutsedge control in soybean (121) and peanuts (41). Pebulate (Sfpropyl butylethylthiocarbamate) also provided yellow nutsedge control in peanuts (40). All preemergence or preplant incorporated herbicides described above control yellow nutsedge for only 6 to 8 weeks. They did not inhibit sprouting of yellow nutsedge but inhibited shoot elongation (5,29,59). Yellow nutsedge grew normally when lesser amounts of herbicide remained in soil (59). Bromacil (S-bromo-3-sggfbutyl-6-methyluracil) and terbacil (3—53337 butyl-5-chloro-6-methy1uraci1) have been used for yellow nutsedge control in non-crop areas. These two herbicides did not kill yellow nutsedge tubers, but killed new shoots from sprouting tubers. The herbicides re- main in the soil a long period of time and eventually yellow nutsedge tubers were killed as food reserves were exhausted (59). Atrazine, a selective herbicide in corn, has been reported to control yellow nutsedge when preplant incorporated (84), however, the control was only fair and erratic (121). Atrazine plus phytobland oil used as a 11 postemergence and split application provided excellent yellow nutsedge control (62). Another triazine, prometryne (2,4-bis (i50propylamino)- 6-(methylthio)-§ftriazine) was reported helpful in controlling yellow nutsedge in corn (121). Cyperquat (l-methyl-4-phenylpyridinium) has been used as postemerg- ence application fer yellow nutsedge control in Kentucky bluegrass (Ega- pratensis L.) (10,50,63) and soybean (56). Pefluidone (1,1,l-trifluoro-Nf(2-methyl-4-(phenylsulfony1)pheny1) methane-sulfonamide) effectively controlled yellow nutsedge either as preplant incorporated, preemergence or postemergence treatment (38,121). Perfluidone showed selectively in cotton (31) and Kentucky bluegrass (50, 63) but in soybean occasional injury occurred. Behavior of Bentazon in Plant and Soil Bentazon (3-isopropyl-1H72,l,3-benzothiadiazin-(4)3H70ne 2,2-dioxide) is a selective postemergence herbicide used to control broadleaf weeds and yellow nutsedge in soybean (55,66,71,101,114), corn (62), rice (Oryza sativa L.), dry beans (Phaseolus vulgaris L.), peanuts (3), and turf-grass (3,50,63). Andersen, 93 El' (2) reported that bentazon controlled wild mustard (Brassica kaber (DC) L.C.), common ragweed (Ambosia artemisiifolia L.), velvet leaf (Abutilon theophrasti Medic), Pennsylvania smartweed (Polygonum pensylvanicum L.), common cocklebur (Xanthium pensylvanicum Wallr.), wild common sunflower (Helianthus annuus L.) and pigweed (Amaranthus sp.). Recently, Oliver, et al. (82) reported that bentazon controlled many species of morning glory (Ipomoea spp.) and was often 12 enhanced by using split applications (46,56,62,63,66,103). Bentazon gives excellent control of young yellow nutsedge plants (101,103). Moreover, the parent tubers have been reported to be killed by the bentazon treatment (101,103). However, Stoller g£_al, (102) reported that in corn fields, pre and postemergence combinations of preemergence alachlor or EPTC and post- emergence treatments with bentazon did not reduce the number of yellow nutsedge tubers after 1 year but after a 2 year period of combination applications, the number of tubers were significantly reduced. The activity of bentazon is dependent on environmental conditions (78,104). Bentazon activity on pigweed was greater under high humidity than low humidity (78). The efficiency of bentazon under high humidity was greater at 10 C than 20 or 30 C (78). Rainfall within 24 hours after application reduced pigweed (78) and velvet leaf (35) control. Wills (127) reported that bentazon was more toxic to common cocklebur grown in wet soil at field capacity than in the dry soil near the wilting point. The translocation of 14C-bentazon was more rapid in common cockle- bur grown in wet soil, under high temperature (35 C), or under high relative humidity (96%). Several surfactants such as the acetylenic surfactants were effec- tive in enhancing the phytotoxicity of bentazon (135). Addition of emulsi- fiable linseed oil and petroleum oil to the spray solution increased the activity of bentazon on pigweed control. The emulsifiable linseed oil and petroleum oil minimized the effect of low humidity and simulated rainfall (78). However, the water-soluble linseed oil formulation was more effective than emulsifiable linseed oil in increasing bentazon acti- vity (79). Water-soluble linseed oil enhanced absorption and transloca- tion of 14C-bentazon in redroot pigweed more than did emulsifiable lin- seed oil, petroleum, or surfactants (80). 13 Mahoney and Penner (68,69) studied the translocation and metabolism of 14C-bentazon in soybean and navy bean (Phaseolus vulgaris L.) and com- pared it to cocklebur and black nightshade (Solanum nigrum L.). 14C- bentazon moved throughout the treated leaf of cocklebur, but little acropetal movement occurred in the trifoliate leaves of navy bean (69). The rate of 14C-bentazon metabolism was more rapid in soybean and navy bean than in cocklebur and black nightshade (68,69). The mechanism of bentazon selectivity in rice and susceptible Cyperus serotinus Rottb. were studied by Mine g£_al, (73). The absorp- tion and translocation of 14C-bentazon was not different between rice and C. serotinus. However, 14C-bentazon was metabolized more rapidly in rice than in C. serotinus 24 hours after treatment. Seven days after herbicide application only 5% of parent 14C-bentazon remained in rice but 50-75% of parent l4C-bentazon remained in C. serotinus. The major metabolite in rice was 6-(3-isopropyl-2,l,3-benzothiadiazin-4-one-2,2- dioxide)-O-8-g1ucopyranoside. Bentazon is a herbicide selective in soybean but not all soybean varieties are resistent to bentazon (120). 14C-bentazon translocation was greater in the susceptible soybean cultivar than the resistant one 14C-bentazon was absorbed (127). Hayes and Wax (44) reported that more in the sensitive cultivar "PI 229.342" (Nookishirohana) than by the toler- ant cultivar "Clark 63". The tolerant "Clark 63" metabolized l4C-bentazon faster than "PI 229.342". Retzlaff and Hamm (87) reported that CO2 assimilation in wheat (Triticum eastivum L.) resistant to bentazon was inhibited after the plant received bentazon. However, C02 assimilation was increased and became normal again after a period of time. The rate of C02 assimilation 14 increase in wheat plants correlated with the rate of 14C-bentazon meta- bolism. 14C—bentazon was metabolized to 6 and 8-hydroxybentazon. Mine and Matsunaka (74) reported that bentazon inhibited the Hill reaction in isolate chloroplast of spinach (Spinacia aleracea L.) and Cyperus serotinus Rottb. However, Boger §t_al, (19) isolate chlor0phasts from algea Bumilleriopsis filiformis and observed that bentazon inhibited photosystems II but not photosystem I. Potter and Wergin (85) observed that light was the essential factor for necrosis development in bentazon treated cocklebur leaves. The higher the illuminance the faster necrosis developed. The length of time required to stop photosynthesis and develop necrosis was about 7 hours after photosynthesis was stopped. This evidence supported the hypothesis that photo—induced toxic by-products resulted from stopping photosynthesis (6). Klepper (64) proposed that the nitrite is a secondary phytotoxic agent responsible fbr initial injury and final death of the plant after herbicide treatment. Bentazon was shown to block light-dependent nitrite reduction and caused nitrite accumulation in green leaf of winter wheat (Triticum aestivum L.) "Centurk" (6S). The mobility and adsorption of bentazon in soil has been studied by Abernathy and Wax (l). Bentazon was anionic in neutral solution and was not adsorbed by soil or by the cation exchange resin, carboxy methyl cellulose (CMC). But bentazon was adsorbed by charcoal and by the anion exchange resin, diethylaminoethyl cellulose (DEAR). It moved with the water front on soil thin layer chromatography plates and also moved through the soil columns. 15 Behavior of Glyphosate in Plant and Soil Glyphosate (N:(phosphonomethyl)glycine), is a translocated non- selective postemergence herbicide for grass and broadleaf weed control (7). The perennial weeds which can be controlled by glyphosate are Johnson grass (Sorghum halepens L. Pers.), Bermuda grass (Cynodon dactylon L. Pers.), paragrass (Brachiaria mutica Forssk. stapf.), quackgrass (Agropyron repens L.), purple nutsedge (Cyperus rotundus L.) (7), field bindweed (Convolvulus purpurea L. ), hedge bindweed (C. sepium L.), and tall morning glory (Ipomoea purpurea L. Roth) (89). Glyphosate also has potential for yellow nutsedge control (20,101). Glyphosate can be used prior to planting corn, soybeans, and cereal crops (7) and fOr turfgrass, Kentucky bluegrass, and alfalfa (Medicago M L.) establishment (76,77). In deciduous fruit trees, applications must be careful to prevent spray drift to other areas except the basal trunk (86). Glyphosate applied in a recirculating sprayer provided effec- tive control of Johnson grass with little soybean injury and greatly in- creasing soybean yields (72). Adding a cationic surfactant to a glyphosate spray solution enhanced the phytotoxicity more than nonionic surfactants for common milkweed (Asclepias syriaca L.) and hemp dOgbane (Apocynum cannabinum L.) control (130). The activity of glyphosate on purple nutsedge increased when applied at 100 percent relative humidity on plants grown at 25 C rather than 35 C (125). More 14C-glyphosate was absorbed and translocated in Bermuda grass at 32 than 22 C and at 100% RH than at 40% RH, this appeared related to greater control (53). l6 Fernadez and Bayer (36) proposed that translocation of glyphosate appeared to follow the typical source-sink relationship after they ob- served 14C-glyphosate translocation in Bermuda grass. In purple nutsedge, 14C-glyphosate moved through the mature tuber to the newly forming tubers at rhizome tips. Tubers were killed when glyphosate was applied to young plants. There is no evidence for 14C- glyphosate metabolism in purple nutsedge (134). In quackgrass, 14C-glyphosate was rapidly absorbed and translocated from the treated leaf to the rhizomes and untreated shoot (95). 14 c- accumulation was greatest in the nodes near the rhizome tip and least in the nodes near the mother shoot with greater numbers of buds killed near the rhizome tip due to large accumulation of glyphosate in this part of quackgrass rhizome (28). Glyphosate may break bud dormancy. Parker (83) reported that sub- lethal doses of glyphosate affected apical dorminance of the perennial weeds , Agropyron repens L., Cyperus rotundus L. and Convovulus arvensis L. Increased number of shoots were formed by 30 cm tall yellow nutsedge plants after treated with glyphosate (20,105). Field bindweed, hedge bindweed, and tall morning glory showed a characteristic response of bud proliferation and shoot proliferation to sub-lethal rates of glyphosate (89). Low concentrations of glyphosate have also been reported to stimu- late basal bud development of sorghum (Sorghum bicolor L.) at normal and above normal temperatures (8). Richard §£_§l, (88) examined the effect of glyphosate on electron transport in pea chloroplast by monitoring oxygen uptake in the present of paraquat or methyl viologen. No inhibition was observed at concentra- tions of 10‘2 to 10"7 M. In soybean leaf cells, glyphosate affected l7 photosynthesis or respiration less than protein or RNA synthesis (23,115). Jaworski (52) reported that glyphosate inhibits the shikimic or aromatic amino acid biosynthesis pathway. The growth inhibition of duck- weed (Lemma gibba) caused by glyphosate can be alleviated by the addition of L-phenyl alanine. Glyphosate may inhibit or repress chorismate mutase and, or prephenate dehydratase. However, Brecke and Duke (23) studying bean discs and isolated cells, indicated that glyphosate inhibited 14C- uracil incorporation into RNA within 3 hours of glyphosate application. Glyphosate directly inhibited ion transport 1 hour after treatment while membrane integrity and the level of ATP were not affected. The ultrastructural effects of glyphosate on Lemma gibba L. was re- ported by Hoagland and Paul (45). Chloroplast, mitochondria, and cell walls were progressively damaged with increased herbicide exposure time, but microtubules, spherosomes, rough endoplasmic reticulum, golgibodies or microbodies were not significantly changed. Sprankle §t_al, (93,94) indicated that glyphosate was inactivated in soil by adsorption to clay and organic matter through the phosphonic d 14C-glyphosate was biodegraded in soil to 14C02 by co- acid moiety an microorganism. However, glyphosate has shown activity in coarse-textured soil when applied at high rates to the soil surface (22,91). The Influence of Ammonium Salts on Herbicide Phytotoxicity Ammonium sulfamate, ammonium sulfate, and ammonium thiocyanate have been classified as a herbicide (6) when used at high rates. However, low rates of ammonium salts have been used to increase herbicide phytotoxicity. Ammonium thiocyanate has been reported to increase the 18 activity of DNOC (4,6-dinitrojg—cresol) (6), endothal(7-oxabicyclo (2.2.1) heptane-2,3-dicarboxylic acid) (6), picloram (4—amino-3,5,6—trichloro- picolinic acid) (128), and glyphosate (18,108). Ammonium salts could affect herbicide absorption and translocation in plants. Ammonium thiocyanate increased amitrol translocation in quack- grass (34). Ammonium sulfate also increased picloram absorption by guava (Psidium cattleianum Sabine) and dwarf bean (Phaseolus vulgarlis L.( (128). The basis for the affect may be the increase in the permeability as re- ported for tritiated water through citrus leaf cuticular membranes (90). Ammonium ion may act at the same or different site of action as the herbicides but cause more injury to the plant than the herbicides alone (81). Ammonium ions prevented phosphorylation and increased the rate of electron flow from plastoquinone to photosystem I (39) and may interact with herbicides that inhibit electron flow. Ammonium ions also suppressed both nitrate and nitrite reductase levels in plant leaves (123) and may enhance nitrite accumulation. When applied in combination with herbicides they may cause more nitrite accumulation in leaves than herbicides alone. The Influence of Ethephon (2-chloroethylphosphonic acid) on Herbicide Phytotoxicity Ethephon has been reported to increase phytotoxicity of dicamba (2,6-dichloro-gfanisic acid) (9) and 2,4,5-T (2,4,5-trichlorophenoxy) acetic acid) (75). Binning gt_al, (9) proposed that ethelene released from ethephon may alter source—sink relationship in plant and increase basipetal movement of herbicides. However, Morey gt_al, (75) reported that ethephon caused a reduction of xylem tissue formation and increased the activity of 2,4,5-T. CHAPTER 2 YELLOW NUTSEDGE (CYPERUS ESCULENTUS) CONTROL WITH BENTAZON AND GLYPHOSATE Abstract The influence of stage of growth and herbicide rate on yellow nut- sedge (Cyperus esculentus L.) control with bentazon (3-isopropyl-1H72, 1,3-benzothiadiazin-(4)3H70ne 2,2-dioxide) and glyphosate (§7(phosphono- methyl)glycine) were evaluated in greenhouse studies. Yellow nutsedge tubers collected in Michigan were sprouted at 21 C and transplanted into soil for the various herbicide treatments in the greenhouse. Bentazon provided greatest control when the plants were 7.6 cm tall. A single 2.2 kg/ha application was more effective than a single 1.1 kg/ha appli- cation. Bentazon was less effective on taller plants, control was less than 50% with a single 2.2 kg/ha application to plants 30.5 cm tall or taller. Split applications of bentazon enhanced control, a time lapse between applications of 5 days provided greater control than 10 or 20 days if the initial application was 1.1 kg/ha and the plants were 30.5 cm tall or less. A single 2.2 kg/ha glyphosate application controlled yellow nutsedge 7.6 cm tall, was less effective on plants 15.2 cm tall and provided no control of taller plants. None of the glyphosate treat- ments resulted in death of the tubers. Under field conditions bentazon provided greater control when split applications were applied to plants 19 20 5 to 7.6 and 10 to 15.2 cm tall than a single application. Extending the time lapse between first and second applications from 10 to 20 days did not affect yellow nutsedge control. Delay of bentazon application until the yellow nutsedge was 20 to 30.5 cm tall failed as a control and resulted in significant soybean (Glycine max (L.) Merr.) yield loss in 1975. Introduction Yellow nutsedge is one of the most serious weed problems in the United States (6,18). It is widely distributed and an increasing problem in most corn (Egg;may§_L.) and soybean producing areas (8,17). It is estimated that one million hectares are infested in the North Central and Northeastern United States and that it is still spreading (5). A previous report indicated that increased control of annual weeds with herbicides and decreased tillage may have contributed to the increased infestation of cropland by yellow nutsedge (2). Both seed and tubers are produced but propagation by tubers is the most important means of dissemination in cultivated crops (2). Most herbicides contributing to yellow nutsedge control kill only the sprouting buds and not the tubers (13,16,20). Tubers contain several buds with various stages of dormancy. It is difficult to kill all the buds on a tuber (l4). Bentazon, a selective postemergence herbicide and glyphosate, a non-selective postemergence herbicide have both shown potential for yellow nutsedge control (3,4,7,l3,19). The objectives of this investigation were to determine the optimum stage of yellow nutsedge growth, bentazon and glyphosate rate, and time lapse between split applications of bentazon for yellow nutsedge control. 21 The effect of bentazon and glyphosate on tuber viability and of bentazon on soybean yield were also examined. Materials and Methods For the greenhouse experiments, yellow nutsedge tubers were collected at East Lansing, Michigan, washed with tap water and placed in petri dishes to sprout in a controlled environment chamber at 21 C. Sprouted tubers with the same shoot length were transplanted into a greenhouse soil mix, one per 946-ml cup. The plants were grown in the greenhouse at 25 :_3 C with supplemental fluorescent lighting, the plants at 7.6 (3 to 4 leaf stage), 15.2 (5 to 6 leaf stage), 30.5 (8 to 9 leaf stage) and 61.0 (12 to 15 leaf stage) cm tall were selected for herbicide appli- cation. Bentazon at 1.1 and 2.1 kg/ha with 0.25% alkyl-aryl-polyglycol ether surfactant1 at 346 L/ha was applied in single and split applications. The time lapse for split applications was 5, 10, and 20 days. Single applications of glyphosate were applied at the same rates used for benta- zon and at the same stage of growth. Treatments were replicated four times in a randomized complete block design. Fourty days after the last bentazon application and 30 days after the glyphosate application the plants were rated for control, number of shoots per plant in each cup, plant height was mreasured, and dry wt determined by harvesting all leaves above the soil surface. The cups containing the roots were placed out-of-doors for a winter cold treatment. The number of shoots that 1This surfactant is known commercially as Citowett, a product of BASF Wyandotte Corp. 22 sprouted in the spring were recorded. Field experiments to study the effect of bentazon on yellow nutsedge control in soybeans were conducted in 1975 and 1976 at the Crop Science Research Farm, Michigan State University, East Lansing, Michigan on sandy clay loam soil with 2.5% organic matter. Treatments were replicated four times in a randomized complete block design. Plot size was 5.0 m by 20 m with four rows in 1.25 m row widths. Bentazon was applied as postemerg- ence single and split applications at 1.1 and 2.2 kg/ha with 0.25% of the same surfactant as used in the greenhouse experiments at 215 L/ha. The time lapse between split applications was 10 and 20 days. Yellow nutsedge plants were 5.0 to 7.6, 10.0 to 15.2 and 20 to 30.5 cm tall, and soybean plants averaged 20.0, 40.0 and 50.0 cm tall, respectively, at the time of bentazon application. Weed control ratings were recorded 20 days after the last herbicide treatment. Two rows of soybeans 10.0 m long in the middle of the plot were harvested for grain yield. The density of new yellow nutsedge shoots in each plot was determined the next spring by using 0.25 m2 quadrat for five random samplings in each plot. Yellow nutsedge in weed-free plots was controlled by hoeing. The grasses in bentazon-treated plots were also controlled by hoeing in 1975 and preplant incorporated trifluralin at 1.1 kg/ha in 1976. The data presented in the tables are the means of two experiments and the field data which is presented for the individual years. Results and Discussion Single applications of bentazon at 2.2 kg/ha controlled yellow nut- sedge in the greenhouse when the plants were 7.6 cm tall, including 23 killing the tubers (Table 1). Death of yellow nutsedge tubers following bentazon application has been reported by Stoller gt_gl, (13). A single application of 2.2 kg/ha of bentazon to yellow nutsedge at 15.2 cm pro- vided only 65% control and reduced the number of shoots, plant height, dry wt, and the number of shoots after regrowth (Table l). Bentazon failed to control yellow nutsedge plants 30.5 and 61.0 cm tall. Regrowth the fellowing spring increased as the height of plants increased. Appli- cation of 2.2 kg/ha bentazon to yellow nutsedge 61.0 cm tall increased the regrowth the fellowing spring perhaps by stimulating tuber production (Table 1). In the greenhouse the 1.1 kg/ha rate of bentazon was ineffec- tive in controlling yellow nutsedge. Split applications of bentazon at the rate of 1.1 kg/ha gave com- plete control of plants 7.6 cm tall with no regrowth evident in spring (Table 2). The most effective time lapse between the first and second bentazon application was 5 or 10 days. Split applications of bentazon provided yellow nutsedge control of plants 30.5 cm tall (Table 2). The 2.2 kg/ha rate in a single application provided only 36% control (Table 1). Since yellow nutsedge leaves are erect, single applications of bentazon may not cover all leaf surfaces and leaves that received less bentazon can grow as normal. The bentazon translocated from yellow nutsedge leaves that received herbicide from a single application may not adequately kill other leaves (13). If the initial bentazon application rate was 1.1 kg/ha and followed with 1.1 and 2.2 kg/ha, the 5-day time lapse between bentazon applica- tions gave complete control of yellow nutsedge 15.2 cm tall (Table 2). Split applications with a lO-day time lapse showed good yellow nutsedge control if the second application rate was 2.2 kg/ha; however, the tubers 24 were not killed. Initial application of bentazon at 2.2 kg/ha followed with 1.1 and 2.2 kg/ha 5, 10, or 20 days later killed the yellow nutsedge feliage (Table 3). The 5-day time lapse between the split treatments was again the most effective time for bentazon for killing the tubers. Split applications of bentazon did not increase the control of plants 61.0 cm tall as all treatments failed (Tables 2 and 3). Single or split applications of bentazon at 1.1 and 2.2 kg/ha did not kill the tubers when applied to plants 30.5 or 61.0 cm tall. The older yellow nutsedge plants have more leaves than the younger plants and spray solu- tions may not have been adequate to cover the whole plant. The leaves of older yellow nutsedge plants may also have thickner cuticles than younger plants allowing less penetration of the herbicide. Data from 1975 and 1976 showed that split applications of bentazon 10 or 20 days apart were more effective for control than single applica- tion (Table 4). Plants in the field may be more susceptible to bentazon as the 1.1 kg/ha rate provided over 50% control of plants 7.6 cm tall. The control ratings indicated that only for the 20.0 to 30.5 cm tall plants the low rate of bentazon was more effective with a lO-day time lapse between applications than a 20-day lapse. Bentazon did not reduce the regrowth of yellow nutsedge shoots, although greenhouse experiments showed that parent tubers could be killed at these rates. These data can be explained by tuber dormancy, as tubers germinated at different times depending on their depth in the soil. A greater portion of the tubers in shallow soil germinated than those deep in the soil (12). The shoots of late germinating tubers would not have received bentazon and can pro- duce tubers again in that season. Repeat applications of bentazon fer two or three seasons may meet the requirements of yellow nutsedge control 25 programs. Soybean yields were not reduced with split applications of 1.1 and 2.2 kg/ha of bentazon applied at the initiation of the first trifoliolate leaves. Reduction of soybean yields occurred when bentazon was applied to 20.0-30.5 cm tall yellow nutsedge (Table 4). Yield reduction may have been the effect of yellow nutsedge and not the effect of bentazon because bentazon failed to control yellow nutsedge when it was taller than 10.0-15.2 cm. Glyphosate applied at the rate of 2.2 kg/ha to yellow nutsedge plants 7.6 cm tall gave 87% control (Table 5). The number of shoots per cup, plant height and dry wt were reduced, although control of yellow nutsedge was not complete nor were the tubers killed (13). Glyphosate at 2.2 kg/ha provided 68% control of plants 15.2 cm tall primarily by reducing plant height and plant dry weight. Glyphosate failed to control plants 30.5 cm tall or taller. Parker (10) reported that sub-lethal doses of glyphosate affected apical dorminance of the perennial weeds, quackgrass (Agrgpyron repens L.), purple nutsedge (Cyperus rotundus L.), and tall morning glory (Convovulus arvensis L.). Glyphosate at 1.1 kg/ha applied to yellow nutsedge 30.5 cm tall stimulated tubers to sprout and develop new shoots (Table 5). This agreed with the results of Boldt and Sweet (3). Glyphosate has been shown to effectively control numerous perennial weeds (1). The pattern of translocation indicates that it moves readily in the phloem (11). This in contrast to bentazon which appears to move primarily in the apoplast (9). It appears paradoxical that the bentazon treatment results in death of the tubers but the glyphosate treatment at the 2.2 kg/ha rate did not. 10. 11. 12. 13. 26 Literature Cited Baird, D.D., R.P. Upchurch, W.B. Homesley, and J.E. Branz. 1971. Introduction of new broad spectrum postemergence herbicide class with utility for herbaceous perennial weed control. Proc. North Centr. Weed Contr. Conf. 26:64-68. Bell, R.S., W.H. Lachman, E.M. Rahn, and R.D. Sweet. 1962. Life and history studies as related to weed control in the northeast. l. Nutgrass. Univ. of Rhode Island Agr. Exp. Sta. Bull. 364, 33 pp. Boldt, P.F. and R.D. Sweet. 1974. Glyphosate studies on yellow nutsedge. Proc. Northeast Weed Sci. Soc. 28:197-204. Hendrick, L.W., M.A. Veenstra, and R.E. Ascheman. 1973. Canada thistle and yellow nutsedge control with split application of bentazon. Proc. North Centr. Weed Contr. Conf. 28:64. Holm, L.G., D.L. Plucknett, J.V. Pancho, and J.P. Herberger. 1977. The World's Worst Weeds. The University Press of Hawaii. Honolulu, 609 pp. Jansen, L.L. 1971. Morphology and photoperiodic responses of yellow nutsedge. Weed Sci. 19:210-219. Ladlie, J.S., W.F. Meggitt, and R.C. Bond. 1973. Preplant incor- porated, preemergence and postemergence application on yellow nutsedge in soybean. Res. Rpt. North Centr. Weed Contr. Conf. 31: 112-113. Lewis, W.H. and A.D. Worsham. 1970. The ten worst weeds of field crops. Nutsedge. Crops and Soils 22:14-16. Mahoney, M.D. and D. Penner. 1975. Bentazon translocation and metabolism in soybean and navy bean. Weed Sci. 23:265-271. Parker, C. 1976. Effects on the dormancy of plant organs (in Herbicides, Physiology, Biochemistry, Ecology, Edited by L.J. Audus). Vol. 1. Academic Press, London 608 pp. Sprankle, P., W.F. Meggitt, and D. Penner. 1975. Absorption, action, translocation of glyphosate. Weed Sci. 23:235-240. Stoller, E.W. and L.M. Wax. 1973. Yellow nutsedge shoot emergence and tuber longevity. Weed Sci. 21:76-81. Stoller, E.W., L.M. Wax, and R.L. Matthiesen. 1975. Response of yellow nutsedge and soybeans to bentazon, glyphosate and perfluidone. Weed Sci. 23:215-221. 14. 15. 16. 17. 18. 19. 20. 27 Stoller, E.W. 1975. Growth, development and physiology of yellow nutsedge. Proc. North Centr. Weed Contr. Conf. 30:124-125. Suwanketnikom, R. and D. Penner. 1975. Yellow nutsedge control with bentazon and glyphosate. Proc. North Centr. Weed Contr. Conf. 30:115. Tumbleson, M.E. and T. Kommedahl. 1962. Factors affecting dormancy in tubers of Cyperus esculentus. Bot. Gaz. 123:186-189. U.S. Department of Agriculture Research Service. 1970. Selected weeds of the United States Agr. Handbook 266, 463 pp. U.S. Department of Agriculture, Agricultural Research Service, Federal Extension Service and Economic Research Service. 1968. Extend and cost of weed control with herbicides and an evaluation of important weeds, 1965. ARS 34-102. 85 pp. Wax, L.M. 1975. Control of yellow nutsedge in field crops. Proc. North Centr. Weed Contr. Conf. 30:125-128. Wax, L.M., E.W. Stoller, F.W. Slife and R.N. Andersen. 1972. Yellow nutsedge control in soybeans. 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Influence of plant height and rate of glyphosate application on yel- low nutsedge grown in the greenhouse 30 days after application. Plant Glyphosate ht rate Control Density Plant ht Dry wt (cm) (kg/ha) (%) (shoots/pot) (cm/plant) (gm/system) 7.6 0 0 aa 6.4 de 48.0 c 2.75 de 1.1 34 d 6.9 e 28.1 b 0.73 abc 2.2 87 f 1.1 a 14.4 a 0.09 a 15.2 0 0 a 6.1 de 44.6 c 2.35 d 1.1 20 be 3.9 bcd 29.3 b 0.67 abc 2.2 69 e 1.6 ab 12.3 a 0.16 ab 30.5 0 0 a 6.7 e 55.0 c 3.78 ef 1.1 5 a 9.6 f 31.4 b 1.90 cd 2.2 29 cd 3.0 abc 29.7 b 1.49 bcd 61.0 0 0 a 5.4 cde 52.7 c 5.66 h 1.1 0 a 4.0 dcd 52.5 c 5.37 gh 2.2 11 ab 4.5 cde 48.9 c 4.16 fg aMeans within columns with similar letters are not significantly differ- ent at the 5% level by Duncan's multiple range test. CHAPTER 3 INFLUENCE OF THE ENVIRONMENT ON YELLOW NUTSEDGE (CYPERUS ESCULENTUS) CONTROL WITH BENTAZON AND GLYPHOSATE Abstract The influence of light intensity, soil moisture, and temperature on yellow nutsedge (Cyperus esculentus L.) control with bentazon (3- isopropyl-lH-2,1,3—benzothiadiazin-(4)3H-one 2,2-dioxide) and glyphosate (N7(phosphonomethyl)glycine) was evaluated in greenhouse and growth chamber studies. Yellow nutsedge tubers collected in East Lansing, Michigan were sprouted at 21 C and then transplanted into soil for the herbicide treatments under various environmental conditions. The higher light intensity (48.4 klux) increased the activity of glyphosate at 1.1 and 2.2 kg/ha. In contrast, bentazon at 2.2 kg/ha caused more injury to yellow nutsedge under the low light intensity (16.1 klux) than under a higher light intensity. Bentazon and glyphosate were more effective under high soil moisture (field capacity) than under low soil moisture conditions. Injury to yellow nutsedge plants 7.6 cm tall increased as the temperature decreased from 35 C to 15 C. If the plants were 30.5 cm tall, greatest injury with bentazon was obtained at 25 C. Glyphosate at 2.2 kg/ha controlled yellow nutsedge 7.6 cm tall grown at 15, 25, and 35 C. But when the plants were 30.5 cm tall at time of treatment, glypho- sate at 2.2 kg/ha provided control only of plants grown at 25 and 35 C. 33 34 Bentazon was more effective than glyphosate in killing yellow nutsedge tubers. Introduction Bentazon, a selective postemergence herbicide for corn (Ega_may§ L.) and soybean, (Glycine max (L.) Merr.) has shown potential for yellow nutsedge control (l,5,6,ll). Occasionally the control has been erratic (12). Temperature, humidity, simulated rainfall, and oil additives have been reported (7) to influence bentazon activity on redroot pigweed (Amaranthus retroflexus L.). Glyphosate, a non-selective postemergence herbicide has also been reported to control yellow nutsedge (3,9). The activity of glyphosate on purple nutsedge (Cyperus rotundus L.) increased when applied at 100 percent relative humidity and to plants grown at 25 C rather than 35 C (13). Thus, glyphosate activity may also be affected by environmental factors. The purpose of this research was to determine the influence of light intensity, soil moisture, and temperature on yellow nutsedge con- trol with bentazon and glyphosate. Materials and Methods Yellow nutsedge tubers collected in East Lansing, Michigan, were placed in petri dishes to sprout in a controlled environment chamber at 21 C. After tubers had sprouted, plants selected for uniformity of shoot length were transplanted to 946-ml cups containing a greenhouse soil mix. 35 Three tubers with shoots were planted per cup for the light intensity and soil moisture studies and four tubers per cup for the temperature study. For the light intensity study, the yellow nutsedge plants were placed in the greenhouse and shaded to receive 16.1 klux and 48.4 klux of light intensity at full daylight and the temperature maintained at 25 :_3 C during the months of March and May. The higher light intensity (48.4 klux) treatment received supplementary fluorescent lighting. The herbicide treatments were applied when the plants were 15.2 cm tall. The experiments were a randomized complete block with a two-way factori- al design and replicated four times. The cups of plants were randomized within blocks every 2 or 3 days. In the soil moisture experiment, the transplanted yellow nutsedge was grown in the greenhouse at 25 1.3 C with supplemental fluorescent lighting. For high soil moisture treatments the plants received 200 ml of water per 946-ml cup daily, whereas those grown under low soil moisture received only 20 ml per cup when they began to wilt. The herbicide treat- ments were applied when the plants were 15.2 cm tall. The experiments were randomized complete block with a two-way factorial arrangement and replicated four times. The cups of plants were randomized within blocks every 2 or 3 days. For the temperature experiment, the yellow nutsedge plants were grown in growth chambers with subirrigation. The temperature treatments were held constant at 15, 25, and 35 C during day and night. Fluorescent and incandescent lighting provided 12.9 klux for the 14-hr day length. Plants 7.6 and 30.5 cm tall received the herbicide treatments. The ex- periments were a completely randomized design with a two-way factorial ‘arrangement and replicated three times. 36 In all experiments bentazon and glyphosate were applied postemergence at the rate of 1.1 and 2.2 kg/ha at 346 L/ha. Bentazon was applied with 0.25% of an alkyl-aryl-polyglycol ether1 surfactant. For all experiments, the plants were returned to the original temperature, light intensity, and soil moisture after herbicide application. Thirty days after herbi- cides were applied, visual injury to yellow nutsedge was rated, plant height was measured, and the plants were harvested for dry weight and determination of tuber viability. All experiments were repeated and all data presented are the means of two experiments with three or four replications each. Results and Discussion Bentazon at 2.2 kg/ha was more active on yellow nutsedge grown under 16.1 klux than under 48.4 klux (Table l). The effect was evident for plant density, height, and percent of parent tubers which rotted at the 2.2 kg/ha rate but not at the 1.1 ka/ha rate. Plants grown under high light intensity may have thicker cuticles than plants grown under low light intensity (4) and thus absorb less bentazon. Light quality or amount of ultraviolet light may also affect cuticle development (4). In contrast to bentazon, glyphosate was more active on yellow nut- sedge grown under 48.4 klux than 16.1 klux at both 1.1 and 2.2 kg/ha rates (Table l). The effect was most evident on plant height. The gly- phosate formulation contained isopropyl amine salt (15) which may increase 1This surfactant is known commercially as Citowett, a product of BASF Wyandotte Corp. 37 absorption and decrease the barrier presented by the cuticle of plants grown under high light intensity. Light may also be necessary for the manifestation of the phytotoxic action of glyphosate similar to that observed for the triazine herbicides (8). Under higher soil moisture conditions bentazon at 1.1 kg/ha pro- vided adequate control of yellow nutsedge by reducing stand density, plant height, and number of viable tubers (Table 2). Increasing the application rate to 2.2 kg/ha did not increase the visual injury rating above the 1.1 kg/ha rate under high soil moisture conditions. Under low soil moisture conditions neither rate provided adequate yellow nut- sedge control. Bentazon has also been shown to be more toxic to common cocklebur (Xanthium pensylvanicum Wallr.) grown in wet soil at field capacity than in the dry soil near the wilting point (14). The translo- cation of 14C-bentazon was rapid in common cocklebur grown in wet soil (14). Greater activity of glyphosate on yellow nutsedge was also apparent under high soil moisture conditions (Table 2). Under water stress the cuticle may be less hydrated, reducing absorption of polar materials (2). Bentazon, especially at 2.2 kg/ha, showed greater phytotoxicity to yellow nutsedge 7.6 cm tall as temperature decreased from 35 to 15 C (Table 3). This was evident for all parameters measured. Yellow nut- sedge showed optimum growth at 25 C (Table 3). High temperatures may encourage thickner cuticle formation and ecrease permeability. Lower temperatures may prolong drying time, promoting foliar absorption. Low temperature (10 C) and high humidity also increased redroot pigweed con- trol with bentazon (7). If the yellow nutsedge was 30.5 cm tall when treated with bentazon at 2.2 kg/ha, greater visual injury was obtained 38 at 25 C (Table 3). Temperature had little effect on injury to yellow nutsedge 7.6 cm tall by 2.2 kg/ha of glyphosate (Table 4). At this rate glyphosate was highly effective at all three temperatures, 15, 25, and 35 C. How- ever, if the yellow nutsedge plants were 30.5 cm tall, glyphosate was more injurious at 25 and 35 C than at 15 C (Table 4). Yellow nutsedge.injury due to bentazon was greatest at low light intensity, high soil moisture, at 15 C for 7.6 cm tall plants and at 25 C for 30.5 cm tall plants. Glyphosate activity was greatest at the high light intensity, high soil moisture, and 25 and 35 C when plants were 30 cm tall. Plants 7.6 cm tall were controlled about equally well with glyphosate in the temperature range of 15 to 35 C. 10. 11. 12. 13. 39 Literature Cited Andersen, R.N., W.B. Lueschen, D.D. Warnes, and W.W. Nelson. 1974. Controlling broadleaf weeds in soybeans with bentazon in Minnesota. Weed Sci. 22:136-142. Ashton, F.M. and A.S. Crafts. 1973. Mode of action of herbicides. John Wiley and Sons, Inc. 504 pp. Boldt, P.F. and R.D. Sweet. 1974. Glyphosate studies on yellow nutsedge. Proc. Northeast. Weed Sci. Soc. 28:197-204. Davis, D.G. 1978. Cuticle development on Citrus mitis leaves as a function of light quality and intensity. Weed Sci. Soc. of Amer. Abstr. No. 171. Kapusta, G. and J.A. Tweedy. 1973. Yellow nutsedge control in soybean. Res. Rpt. North Centr. Weed Contr. Conf. 30:108 and 110- 111. Ladlie, J.S., W.F. Meggitt, and R.C. Bond. 1973. Preplant incor- porated, preemergence and postemergence application on yellow nut- sedge in soybeans. Res. Rpt. North Centr. Weed Contr. Conf. 30: 112-113. Nalewaja, J.D., J. Pudelko, and K.A. Adamczewski. 1975. Influence of climate and additives on bentazon. Weed Sci. 23:504-507. Shimabukuro, R.H., V.J. Masteller, and W.C. Walsh. 1976. Atrazine injury: relationship to metabolism, substrate level, and secondary factors. Weed Sci. 24:336-340. Stoller, E.W., L.M. Wax, and R.L. Matthiesen. 1975. Response of yellow nutsedge and soybeans to bentazon, glyphosate and perfluidone. Weed Sci. 23:215-221. Suwanketnikom, R. and D. Penner. 1976. Environmental influence on yellow nutsedge control with bentazon and glyphosate. Proc. North Centr. Weed Contr. Conf. 31:141. Tweedy, J.A., G. Kapusta, and O. Kale. 1972. The effect of several herbicides on nutsedge control in soybeans. Proc. North Centr. Weed Contr. Conf. 27:28-29. Wax, L.M. 1975. Control of yellow nutsedge in field crops. Proc. North Centr. Weed Contr. Conf. 30:125-128. Wills, 6.0. 1974. Effect of temperature, relative humidity, soil moisture and surfactant on the toxicity of glyphosate to cotton and purple nutsedge. Weed Sci. Soc. of Amer. Abstr. No. 275. 14. 15. 4O Wills, G.D. 1976. Translocation of bentazon in soybean and common cocklebur. Weed Sci. 24:536-540. Weed Science Society of America. 1974. Herbicide Handbook. Champaign, IL. 430 pp. 41 oamfluass m.:mo::0 x9 ~o>o~ mm on» an acouowwdv saucmofimwcwflm no: .u now owcmu mum muouuofi umawsflm so“: youoswumm.so>flw a how ovfioflnuoz co>flm a easy“: nemoZD .zumov a 0g .xusncfl o: u 0 uoflmom 0H 6» 0 a :0 eye: mwcfiumu flouucoum an m o 0w a N.0 an 5.0 m.v a 0.m~ m ~.~ be m.v o 0.0 o 0.m m.~ on MA on m m ~.0 on 0.~ m.m n n.5m n 5.0 n m.o 0 m.0 n 0.m H.~ w 0 m 0 0 m.~ o m.~ n.mm 0 0.0v n 0.0 no m.v a 0.0 m 0.0 0 oummocmxdo u on 0 00g on 5.0 m m.0 0.0m m m.~ n n.~ m v.0 o ~.o v v.0 ~.~ 9 mm 0 mm b 0.0 pm v.0 ~.w~ u 0.~N 0o 0.m on H.m a o.m n n.m H.~ m 0 a 0 o n.~ o 0.“ «.mm o 0.0v 0 ~.0 u 0.0 a 0.0 an 0.0 0 acumucom x=~x usux xsax xsfix xsqx xSHx xsax xsax xsax usax Aan\wxv moufiownuoz v.0v H.0H v.0v H.0H v.0v H.0H v.0v «.oa v.0v ~.0H comm Awu coupon maoumxw acm~m\amu mucmfim\eou mmso\muoozm0 uncanny was» mucosa Havana u: xno u: acmum xufimcoo shone“ «asmfi> .ucoaumouu mcwzoaaom mxmv 0m venomous Ham» so ~.m~. owuomusc zoaaox co xufl>fiuom unamozmxaw 0:0 :ONmucon :o xoflmcoHcfl unwfia mo poomwo one .4 oanmh 42 oamfiuaaa m.:oo::0 xn ~o>o~ am on» no acouowwflv xaucooflwficmflm no: ouo .umou omcop muouuoH umaaefim no“: uouoEmumn co>wm a how onfloflnuo; 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Yellow nutsedge tubers collected at East Lansing, Michigan, were sprouted at 21 C and transplanted into soil in the greenhouse. Bentazon and glyphosate were applied at 1.1 kg/ha, alone and in combination with 2,4-D or ethephon at 1.1 or 2.2 kg/ha or with urea or ammonium salts at 4.5 and 9 kg/ha, when the plants were 15 cm tall. After 30 days, the plants were rated for visual herbicide injury, the shoots per cup counted, and plant height and dry weight measured. Ammonium phosphate, ammonium chloride, ammonium sulfate, and ammonium thiocyanate in combination with bentazon significantly increased the injury ratings, reduced the stand density, plant height, and dry weight of shoots when compared to benta- zon alone. All additives evaluated increased glyphosate activity as in- dicated by increased yellow nutsedge injury rating primarily by reducing the stand density compared to glyphosate alone. Varying the pH of the 45 46 spray solution from 3 to 11 did not affect bentazon or glyphosate acti- vity. Introduction Phytobland oils and organic surfactants have often been used as spray additives for postemergence herbicide applications. However, in- organic salts can also be used as additives to increase herbicide acti- vity. Amitrol-T, the combination of amitrol (3-amino-s-triazole) and ammonium thiocyanate has become a commercial product (13). Ammonium sulfate has been reported to increase the activity of picloram (4-amino- 3,5,6-trichloropicolinic acid) (15), endothal (7-oxabicyclo(2.2.l)heptane- 2,3-dicarboxylic acid) and DNOC (4,6-dinitro-g-cresol) (1). Less than Optimum yellow nutsedge control with bentazon and glypho- sate occurs if the plants are too tall, over 15 cm, or under low soil moisture conditions (11,12). Suwunnamek and Parker (10) reported in- creased purple nutsedge (Cyperus rotundus L.) control with glyphosate upon addition of ammonium sulfate to the spray solution. Butyl acid phosphate and ammonium sulfate have been reported to increase glyphosate efficacy for quackgrass (Agropyron repens (L.) Beauv.) control (3). The objective of this research was to evaluate potential additives to increase the activity of bentazon and glyphosate on yellow nutsedge. 46 spray solution from 3 to 11 did not affect bentazon or glyphosate acti- vity. Introduction Phytobland oils and organic surfactants have often been used as spray additives for postemergence herbicide applications. However, in- organic salts can also be used as additives to increase herbicide acti- vity. Amitrol-T, the combination of amitrol (3-amino-s-triazole) and ammonium thiocyanate has become a commercial product (13). Ammonium sulfate has been reported to increase the activity of picloram (4-amino- 3,5,6-trichloropicolinic acid) (15), endothal (7-oxabicyclo(2.2.l)heptane- 2,3-dicarboxylic acid) and DNOC (4,6-dinitro-g-cresol) (1). Less than Optimum yellow nutsedge control with bentazon and glypho- sate occurs if the plants are too tall, over 15 cm, or under low soil moisture conditions (11,12). Suwunnamek and Parker (10) reported in- creased purple nutsedge (Cyperus rotundus L.) control with glyphosate upon addition of ammonium sulfate to the spray solution. Butyl acid phosphate and ammonium sulfate have been reported to increase glyphosate efficacy for quackgrass (Agropyron repens (L.) Beauv.) control (3). The objective of this research was to evaluate potential additives to increase the activity of bentazon and glyphosate on yellow nutsedge. 47 Materials and Methods Yellow nutsedge tubers collected in East Lansing, Michigan, were washed with water and placed in petri dishes to Sprout in a controlled environment chamber at 21 C. After sprouting, tubers with similar shoot length were transplanted, one per cup, to 946-ml cups containing green- house soil. The plants were grown to 15 cm in height in the greenhouse at 25 :_2 C with supplemental fluorescent lighting. Bentazon and gly- phosate were applied at 1.1 kg/ha at 346 L/ha. An alkyl-aryl-polyglycol ether1 surfactant at 0.25% v/v was applied applied with the bentazon. Glyphosate was applied as the formulated isopropylamine salt. 2,4-D and ethephon were applied at 1.1 and 2.2 kg/ha. All ammonium salts were applied at 4.5 and 9 kg/ha. After the ammonium salts were mixed with bentazon and glyphosate, the solution pH was measured. To determine the effect of pH on the spray solution, the pH of 1.1 kg/ha bentazon and glyphosate solutions were adjusted with HCl and KOH. Thirty days after treatment the plants were rated for visual injury, the stand density in the cup determined, plant height and dry weight determined. All data presented are the means of two experiments with three repli- cations per experiment. Results and Discussion 2,4-0 at 1.1 and 2.2 kg/ha failed to increase the activity of bentazon applied to yellow nutsedge 15 cm tall (Table l). Ethephon at 1This surfactant is known commercially as Citowett, a product of BASF Wyandotte Corp. 48 1.1 kg/ha applied in combination with bentazon at 1.1 kg/ha resulted in greater stunting than either treatment alone (Table l). Urea and ammoni- um acetate at 4.5 and 9 kg/ha had little or no effect on bentazon activity (Tables 1 and 2). In contrast, ammonium chloride, ammonium phosphate, ammonium sulfate, and ammonium thiocyanate at 4.5 and 9 kg/ha markedly increased bentazon phytotoxicity to yellow nutsedge (Table 2). A single application of bentazon at 1.1 kg/ha did not provide ade- quate control of yellow nutsedge 15.0 cm tall in the greenhouse as previously reported field results (11). But in combination with ammonium salts, bentazon activity was greatly enhanced. The visual injury rating increased whereas the number of shoots per cup, plant height, and dry weight of shoots per cup decreased. Nash (8) has proposed three possible site of pesticide interactions: (a) altered penetration at the site of absorption, (b) one pesticide affecting a primary metabolic pathway and the other secondary pathway, and (c) both pesticides affecting the same metabolic pathway and possibly ammonium salts could affect bentazon absorption, translocation, or act at a different or the same site of action as bentazon. Wilson and Nishimoto (16) reported that ammonium chloride, ammonium nitrate, ammonium phos- phate, and ammonium sulfate increased absorption of 14C-picloram by guava (Psidium cattleianum Sabine) leaves and indicated that the ammonium ion was primarily responsible for the enhancement effect. Monovalent cations increase the permeability of tritiated water by citrus leaf cuticular membranes (9). 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Table 2. (gm/plant system) Dry wt Plant ht (cm/plant) Density (shoots/cup) Visual Injury rating after 30 days3 pH of spray solution Bentazon rate (kg/ha) Rate (kg/ha) Ammonium salts 42.2 a 2.32 c 9.5 a 0.0 ab 0.5 a Ammonium 40.7 a 1.48 ab 1.77 be 1.97 be 0.94 a 7.3 a 6.5 a 5.1 acetate 44.3 a 0.0 a 7.1 4.5 45.2 a 6.7 a 6.0 a 6.0 a 0.0 a 0.2 6.7 9.0 35.3 a 1.1 7.0 1.1 4.5 1.20 ab 34.3 a 2.0 a 7.2 9.0 2.32 b 1.48 b 1.80 b 2.09 b 0.31 a 9.5 41.8 b 40.7 b 0.0 a 0.5 Ammonium 7.3 b 7.2 b 8.5 5.1 1.1 chloride 44.3 b 45.3 b 0.0 a 0.0 a 7.0 b 9.0 c 5.9 5.6 4.5 9.0 a 9.8 2.0 a 1.1 0.21 a 5.7 a 1.8 a 5.1 1.1 511 2.32 c 1.48 b 2.18 c 41.8 b 40.7 b 46.7 b 9.5 c 7.3 bc 0.0 a 0.5 5.1 1.1 phOSphate Ammonium 7.8 be 6.3 b 0.0 4.5 1.74 bc 0.41 a 46.7 b 9.0 16.3 a 2.5 a 5.3 b 5.8 b 1.1 0.37 a 15.0 a 2.5 a 1.1 2.32 c 1.48 b 2.48 c 41.8 cd 40.7 c 9.5 c 7.3 c 7.5 <6!!! om CO 5.1 sulfate Ammonium 48.8 d 49.3 d 20.8 d C 4.5 9.0 4.5 2.61 c 8.8 c 4.0 b 0.0 a 2.8 b 9.7 c 0.46 a 5.1 0.17 a 1.3 a 0.5 a 5.0 9.0 9.5 c 41.8 b 2.32 c 40.7 b 0.0 a 0.5 a Ammonium 1.48 b 2.12 bc 2.00 be 7.3 b 6.8 5.1 O 4.5 thiocyanate 47.5 b 39.5 a 0.0 a 6.2 «In! om III—1 “a l\tn CO 7.3 bc {3.0.0 Dunn 0000 m0 H—i HM mo V71 aRatings were on a 0 to 10 scale, 0 = no injury, 10 = death. bMeans within columns for a given ammonium salt with similar letters are not significantly different at the level by Duncan's multiple range test. 5% SS .umou owcmn o202u2sa m.smu030 xs 2o>o2 00 osu om aco2o0020 x2pcmu2020020 no: ohm muouuo2 2m22E2m su23 0:5:2ou c2su23 mcmon .somo0 u 02 .xusncfi o: u 0 .o2mum 02 on 0 m so onoz 00:2um0m sm 00.0 m 0.00 m 0.0 m 0.0 22 2.2 n 02.2 m 0.00 m 0.0 m 0.0 02 2.2 m 00.0 m 0.00 m 0.0 m 0.2 0 2.2 pm 00.0 m 0.00 o 0.0 m 0.0 0 2.2 0m 00.0 m 0.00 m 0.0 m 0.0 0 2.2 pm 00.0 m 0.00 m 0.0 m 0.2 0 2.2 pm 00.0 m 0.00 m 0.0 m 0.0 0 2.2 m 00.0 m 0.00 m 0.0 m 0.2 0 2.2 sm 00.0 m 0.20 m 0.0 m 0.0 0 2.2 0 $5 a 0.00 m 0.0 a o.o 2.2 32.23 c: 2.2 o 00.0 m 0.00 m 0.0 sm 0.0 0 maopmxm mp=m2a\5u0 Amouxmuoosmv mmxm0 00 Houmm :o2us2om 2ms\0xv ucm2m\600 as usm20 xp2mco0 0:2um2 mo :0 oumh u: 220 22:“:2 2mom2> coumucom .coumucon su23 22mu Eu 02 o00omuss 3622ox mo 2onucou :o :0 mo uuommo ose .0 o2smh 55 .umou owomn o2m2u2ss 0.:mu030 xn 2o>o2 00 osp um acouowM20 x2ucmu2w2cw2m no: ohm mnouuo2 Hm22E2m su23 maas2ou c2su23 mcmoZQ .sumo0 u 02 .xusnc2 o: u 0 .o2mum 02 on 0 m :o ouo: 00:2um0m cm 00.0 m 0.00 m 0.0 m 0.0 22 2.2 s 02.2 o 0.00 m 0.0 m 0.0 02 2.2 m 00.0 m 0.00 m 0.0 m 0.2 0 2.2 so 00.0 m 0.00 m 0.0 m 0.0 0 2.2 cm 00.0 m 0.00 m 0.0 m 0.0 0 2.2 sm 00.0 m 0.00 m 0.0 m 0.2 0 2.2 cm 00.0 m 0.00 m 0.0 m 0.0 0 2.2 m 00.0 m 0.00 m 0.0 m 0.2 0 2.2 sm 00.0 m 0.20 m 0.0 m 0.0 0 2.2 pm mo.o m 0.00 m 0.0 a o.o 22.00 um=2vm 0: 2.2 u 00.0 m 0.00 m 0.0 nm 0.0 0 maoumxm muco2m\su0 202u\muoosmv om>m0 00 noumm :o2us2om 2ms\0xv usm2m\awv us ucm2m xu2mso0 0:2pmn mo mm oumn a: 090 knahc2 2m302> :onmuoom .sonmucos su23 22m» Eu 02 o00omu3: 3022ox mo 2ouucou co :0 mo uuommo och .0 o2smh 56 00 osu pm u:o2o0020 x2usmu2020020 .umou owcmu o2m2u2sa 0.:muss0 00 2o>o2 no: ohm muouuo2 um22E2m s02: o>2u200m =o>20 m mom mcss2ou :2su23 mcmo20 .sumo0 u 02 .xusns2 o: u 0 .o2mum 02 ca 0 m so ouoz 00:2um0m m 00.0 m 0.02 m 0.2 0 0.0 2.2 0.0 m 00.0 m 0.02 m 0.0 u 0.0 2.2 0.0 s 00.0 0 0.00 0 0.0 m 0.0 0 0.0 s 00.0 s 0.00 s 0.02 m 0.0 0 0.0 m 00.0 o 0.00 0 0.0 n 0.0 2.2 0 0 00.0 s 0.00 a 0.0 m 0.0 0 0 mop: m 00.0 m 0.02 m 0.0 u 0.0 2.2 0.0 m 00.0 m 0.02 m 0.0 u 0.0 2.2 2.2 0 00.2 s 0.00 a 0.02 m 0.0 0 0.0 0 02.0 0 0.20 0 0.0 m 0.0 0 2.2 m 00.0 o 0.00 n 0.0 s 0.0 2.2 0 0 No.0 0 0.00 a 0.0 a 0.0 o o cosmozum mm 00.0 m 0.02 m 0.0 u 0.0 2.2 0.0 m 00.0 m 0.02 m 0.0 u 0.0 2.2 2.2 up 00.0 a 0.00 0 0.0 no 0.0 0 0.0 o 00.2 0 0.00 0 0.0 nm 0.0 0 2.2 cm 00.0 m 0.00 u 0.0 on 0.0 2.2 0 0 00.0 o 0.00 on 0.0 nm 0.0 0 0 0-0.0 Aaoumxm Auom20\au0 20:u\mpoosmv mmxm0 00 Hoomm 2ms\0xv mms\0sv o>2u200< u:m20\500 as unm20 xu2mso0 mcwuon oumu oumm as >20 xnsns2 2m=m2> oummosmx20 .mon: no .cogmosuo .0-0.0 0:20 oummos0x20 mo =02umu2200m oucomuosoumom su23 22m» Eu 02 o00omuoc 3o22o» mo 2ohucou .0 o2smh (gm/plant system) Dry wt Plant ht (cm/plant) Q l v N U) 3 .24 Q4 0.) u (U W O E ,2... DO 14.. O F: ° ’5‘. 'H H :3 (U >sU U H\ "-1 "-40 0-1 W“ a :8 Cd 92: U) 0 v U C. 0 00 H O E “’m .4 E? >. m :3 m 0 "-1 'U 94 C00 «4‘30 £3 '01”) H HP "-1 (6463-: 3 331-10) 0 H H "-4 '«H H > Cd (13 4..) E U m G) H 4H (U r-\ d.) £13003 00 0441: “U .CM\ 0 EH00 m 24 H v-1 U .‘3 U ‘3 3m 00 o-IH H3 0 m >064 C0 0 0.1: ‘H H\ 0'4 who I: 04.34 HO v 04: HQ: HQ) {2.2 OH UO 0 Q) V > 'H O H T 36‘ .0 <3 '0 E-' < 2.02 d 0.65 ab 1.09 c 0.92 bc 0.48 a 0.65 ab 43.5 c 20.2 a 29.3 b 27.2 b 19.2 a 19.6 a 8.5 bc 9.8 c 6.2 b 6.0 b 3.3 a 3.2 a .0 (600 LONN CV? 0.0 ab 3.2 be 0.3 ab v—I HH 0 00°00 v-O Hv-G v—INHN HNHN 2,4-D 2.02 b 0.65 a 2.13 b 1.75 b 0.45 a 0.50 a 43.6 b 20.2 a 41.0 b 40.8 b 19.4 a 17.2 a 8.5 b 9.8 b 8.7 b 10.0 b 2.2 a 2.5 a (ti—DMCUUU ONOOMU) 000000 H o-u-a OoOOoo 2: 04—4 HNHN HNv—GN Ethephon .omsnmm 0000000 000000 NONNOO 0000mm OONOOLnMO 00000100 Vva—«o-I 3.0.0.05“: moomozmoo oomOOONo-I o-Q M.DGCUU'U ONOOQM OMOOMQ HH 0 .oo 0 o LOOLDO '3’me <6 0 H D aRatings were on a 0 to 10 scale, 0 = no injury, 10 = death. bMeans within columns for a given additive with similar letters are not significantly different at the 5% level by Duncan's multiple range test. of glyphosate plus various Control of yellow nutsedge 15 cm tall with postemergence application ammonium salts. Table 5. Dry wt (gm/plant system Visual injury pH of Glyphosate Plant ht (cm/plant) Density (shoots/cup) rating after 30 daysa Rate rate spray (kg/ha) solution (kg/ha) Ammonium salts 2.02 b 8.5 b 43.6 b 9.8 0.0 ab Ammonium 0.65 a 3.2 b 5.1 5.4 1.1 acetate 2.32 b 2.05 b 46.7 b 43.0 b 19.0 a 20.0 a 0.0 a 8.8 0.0 a 4.0 b 4.8 b 4.5 7.8 5.5 9.0 0.48 a 4.0 a 1.1 5.3 4.5 0.57 a 4.3 a 1.1 9.0 2.02 b 43.6 b 20.2 a 8.5 c 0.0 a Ammonium 0.65 a 9.8 c 3.2 b 5.1 1.1 chloride 2.08 b 43.3 b 41.0 b 20.7 a 7.3 be 0.0 a 0.0 a 5.8 c 5.9 4.5 1.66 b 0.60 a 7.3 bc 3.7 a 5.6 9.0 4.5 4.8 4.9 1.1 0.57 a 19.7 a 4.0 ab 7.2 c 1.1 557 43.6 b 2.02 b 20.2 a 8.5 b 0.0 a 3.2 Ammonium 0.65 a 9.8 b 5.1 1.1 phosphate 42.5 b 2.13 b 44.7 b 7.7 b 8.0 b 2.3 a 2.3 a 0.0 a 5.0 4.5 1.86 b 0.40 a 0.0 a 8.7 c 9.0 4.5 19.0 a 19.0 a 5.0 1.1 0.50 a 7.7 c 1.1 9.0 8.5 be 43.6 c 2.02 c 9.8 c 0.0 a Ammonium 0.65 a 20.2 a 3.2 b 5.1 1.1 sulfate 1.5 ab 6.8 b 45.7 c 1.95 c 0.0 a 5.7 4.5 1.42 b 0.50 a 0.40 a 36.0 b 17.3 a 17.0 a 7.3 bc 2.7 a 2.7 a 5.8 4.6 4.5 9.0 8.3 c 8.8 c 1.1 1.1 9.0 2.02 c 0.65 a 43.6 c 8.5 c 0.0 a Ammonium 20.2 a 9.8 d 3.2 b 0.0 a 0 1.1 5.1 4.5 thiocyanate 1.19 b 1.07 b 0.55 a 36.0 b 34.3 b 20.0 a 7.0 b 5.7 a 0.0 a 5.9 4.6 5.5 a 2.2 ab 1.1 4.5 20.0 a 0.54 a 9.7 d 3.3 b 1.1 9.0 10 = death. = no Injury, aRatings were on a 0 to 10 scale, 0 bMeans within columns for a given ammonium salt with similar letters are not significantly different at the 5% level by Duncan's multiple range test. 58 .umou owcmn o2m2u2se 0.:mucs0 >0 2o>o2 00 osu um ucouomw20 >2pcmu202002m Ho: ohm mnouuo2 hm22E2m sp23 maes2ou :2su23 mcmozs .sumo0 u 02 .>u:n:2 o: u 0 .o2mum 02 ca 0 m so o2o3 mwc2um0m 0 00.0 nm 0.20 m 0.0 s 0.0 22 2.2 0 00.0 0 0.00 m 0.02 s 0.2 02 2.2 m 00.0 m 0.02 m 0.0 s 0.0 0 2.2 m 00.0 m 0.02 m 0.0 s 0.0 0 2.2 pm 00.0 m 0.02 m 0.0 s 0.0 0 2.2 o 00.0 pm 0.02 m 0.0 s 0.0 0 2.2 m 00.0 m 0.02 o 0.0 s 0.0 0 2.2 o 00.0 m 0.02 o 0.0 0 0.0 0 2.2 m 00.0 m 0.02 m 0.0 0 0.0 0 2.2 nm 00.0 nm 0.02 m 0.0 0 0.0 m2.00 0oumsn0m go: 2.2 o 00.0 o 0.20 m 0.0 cm 0.0 0 25oum>m musm2m\auv nmsu\muoosmv mm>m0 00 nopwm 0620:2om mms\0xv usm20\500 us unm20 >uHmso0 wswumn mo :0 oumn 23 >20 >Hsncw 2m302> soumpcom .oummos0>20 su23 22mu Eu 02 o00omusc 3022o> mo 2o2ucou :o :0 mo uuommo ose .0 o2pmh CHAPTER 5 INFLUENCE OF STAGE OF GROWTH, ENVIRONMENTAL FACTORS AND ADDITIVES ON 14C-BENTAZON AND 14C-GLYPHOSATE ABSORPTION AND TRANSLOCATION BY YELLOW NUTSEDGE (CYPERUS ESCULENTUS) Abstract Absorption and translocation of 14C-bentazon (3-isopropyl-lH-2,l,3- benzothiadiazin-(4)3H-one 2,2-dioxide) and 14C-glyphosate (N-(phosphono- methyl)glycine) in yellow nutsedge (Cyperus esculentus L.) was studied in the greenhouse and laboratory with tubers collected in Michigan, grown in quartz sand, subirrigated with Hoagland's solution, and treated with l4C-bentazon and 14C-glyphosate applied to the second oldest leaf when the plants were 7.6 and 15.2 cm tall. Greater 14C—bentazon absorption and translocation was observed with plants 7.6 cm tall than 15.2 cm. Absorption and translocation increased during the time period 4 to 24 hour after 14C-bentazon application. 14C-bentazon moved both acropetally and basipetally and translocated into parent tubers of plants 7.6 and 15.2 cm tall. Split applications of bentazon and addition of ammonium sulfate at 9 kg/ha to the spray solution increased absorption of 14C- bentazon and translocation from the treated leaf to other leaves of plants 15.2 cm tall. Yellow nutsedge grown in EPTC (S-ethyl dipropyl- thiocarbamate) treated sand culture and in low soil moisture conditions absorbed less 14C-bentazon 24 hour after treatment than plants grown in 59 60 normal soil conditions. Yellow nutsedge plants 15.2 cm tall absorbed more 14C-glyphosate than plants 7.6 cm tall. However, translocation was more extensive in plants 7.6 cm tall than those 15.2 cm tall, 1 and 5 days after treatment. No 14C-glyphosate was translocated to the tubers of yellow nutsedge if applied alone. Ammonium sulfate at 9 kg/ha in com- bination with 14C-glyphosate rapidly increased absorption and basipetal movement of 14C-glyphosate in plants 15.2 cm tall 4 to 24 hours after treatment. Ethephon (2-chloroethy1phosphonic acid) at 2.2 kg/ha in com- bination with 14C-glyphosate increased absorption and basipetal movement of 14C-glyphosate from the treated leaf to roots, rhizomes, and parent tubers of yellow nutsedge plants 15.2 cm tall within 1 and 5 days after treatment. Yellow nutsedge grown under low light intensity absorbed less 14C-glyphosate than plants grown under high light intensity. Introduction Bentazon is a selective postemergence herbicide used for weed con- trol in corn and soybean (1,5,6,7). It is particularly effective for yellow nutsedge control. Glyphosate is a nonselective postemergence herbicide that has been used for purple nutsedge (Cyperus rotundus L.) (24) and yellow nutsedge control (4,12). The activity of bentazon and glyphosate on yellow nutsedge is in- fluenced by many factors, including stage of plant growth, split appli- cation of herbicide, rate of herbicide, additives, and environmental conditions (13,14,15). 1VAC-bentazon is translocated both acropetally and basipetally in soybean with the translocation increasing to 5 days after treatment (7). 61 Susceptible soybean translocated more bentazon than the tolerant culti- vars (22). The translocation of 14C-bentazon has been related to the susceptibility of weed species to bentazon (9). Glyphosate has been shown to translocate from treated leaf to un- treated shoot and develoPing tillers of yellow nutsedge (11). In purple nutsedge, the translocation of 14C-glyphosate was greatest in young plants (24). The objective of this study was to determine the influence of stage of plant growth, split application of herbicide, additives and environ- mental conditions on absorption and translocation of 14C-bentazon and l4C-glyphosate on yellow nutsedge. Materials and Methods Yellow nutsedge tubers collected at East Lansing, Michigan, were germinated in controlled environmental chambers at 21 C. Tubers with similar size shoots were selected and planted 2 cm deep in quartz sand in 294-ml cups. These were subirrigated with a modified Hoagland's No. 1 solution adjusted to pH 6.5. For the dry soil treatment, 10 ml of Hoagland's solution were sub- irrigated when plants started to wilt. EPTC at 0.56 kg/ha was applied as preplant incorporated treatment to sand before planting the yellow nutsedge tubers for the EPTC combination with bentazon. The plants were maintained under greenhouse conditions at 25 :_3 C with supplemental fluorescent lighting to obtain a 14 hour day and 30.2 klux. To determine the influence of low light intensity on glyphosate absorption and trans- location, the plants were exposed to 16.1 klux of light. Plants were 62 allowed to grow to 7.6 or 15.2 cm in height and then treated with the postemergence 14C-herbicide. Ammonium sulfate at 9 kg/ha and ethephon at 2.2 kg/ha were applied as spray additives just prior to the applica- tion of the 14C-herbicides. For the split application of bentazon, 1.1 kg/ha of bentazon was applied to yellow nutsedge plants 15.2 cm tall 5 days before the 14C-bentazon was applied. The 14C-bentazon, labelled in the 10 position, had a specific activity of 13.7 uCi/mmole and was puri- fied to 98%. The methyl labelled 14C-glyphosate had a specific activity of l uCi/mmole and was purified to 97%. It was then converted from the acid to the isopropyl amine salt and applied with 0.8% nonionic poly- ethoxylated tallow amine surfactant (MON 0818). The second oldest leaf of a plant from each treatment was selected for the 14C-herbicide application. Each leaf received a 5 ul dr0p con- taining 0.08 uCi of 14C-bentazon and 0.05 uCi of 14C-glyphosate. The drop of 14C-herbicide was placed in the middle of the leaf between two lanolin bars perpendicular to the length of the leaf. The plants were harvested 4 or 24 hours, or 5 or 10 days after l4C-herbicide application, depending on treatment. The plants were harvested by washing the sand from the roots, rhi- zomes, and tubers with three successive water rinses. Plants were dis- sected into above-treated area, below-treated area, other leaves, roots and rhizomes, and parent tuber and then freeze-dried. The treated spot on the treated leaf was discarded since the herbicide in this area was not considered to be translocated. For the translocation study, plants were radioautographed to determine the pattern of distribution. Plant parts were combusted by the Schoeniger combustion method of Wang and Willis (18) to quantitatively determine translocation. The 14C was then 63 radioassayed by liquid scintillation radioassay. All data presented are the means of two experiments with two replications each. Results and Discussion More 14C-bentazon was absorbed by leaves of yellow nutsedge 7.6 cm tall than 15.2 cm (Table l). The thinner cuticular wax covering of the leaves of the younger yellow nutsedge plants allowed greater penetration of the 14C-bentazon into the leaves. This may explain the greater sus- ceptibility of the younger yellow nutsedge to bentazon previously reported (13). The amount and percent of 14C-bentazon absorbed by yellow nutsedge 7.6 cm tall increased from 4 to 24 hour after treatment. 14C-bentazon moved both acropetally and basipetally (Table 2 and Figures 1 and 2). 14C-bentazon was translocated to roots and rhizomes within 4 hours and to the parent tuber within 24 hours. The greatest translocation of 14C-bentazon was observed when plants were harvested 5 days after herbicide application (Figure 1). The translocation of 14C- bentazon to the parent tuber of relatively small plants, 7.6 cm tall may explain the previously reported (13) effectiveness of bentazon in killing tubers. Ammonium sulfate increased the total percentage of 14C-bentazon absorbed by plants 15.2 tall both 4 hours and 24 hours after treatment (Table 1). This is consistent with the increased bentazon activity ob- served when bentazon was combined with ammonium sulfate (15). Wilson and Nishimoto (19) reported that ammonium sulfate increased picloram activity and absorption by guava (Psidium cattleianum Sabine) and 'Bountiful' dwarf bean (Phaseolus vulgaris L.). They concluded that 64 the ammonium ion was responsible for the enhancement (20). Monovalent cations like ammonium ion increased penetration of tritiated water through citrus leaf cuticles (10). Similarly, it may increase 14C-benta- zon absorption by cuticular penetration but not via stomatal penetration as stomata are absent on the adaxial leaf surface of yellow nutsedge (21). Four hours after application of 14C-bentazon in combination with ammonium sulfate, more 14C-bentazon was found in the leaf area below the treated area but less was found in roots and rhizomes (Table 2). However, ammonium sulfate did not increase 14C-bentazon translocation to the parent tuber l and 5 days after treatment (Table 2, Figure 2). 14C-bentazon movement is primary acropetal (7) and ammonium sulfate may not be able to change this translocation pattern in yellow nutsedge. Split applicationSCHFbentazon simulated by applying bentazon 5 days peior to application of l4C-bentazon increased 14C-bentazon absorption by plants 15.2 cm tall (Table 1). These results are consistent with the increased bentazon activity observed when split applications of bentazon in other greenhouse studies (13). It appears that bentazon action in- volves increasing permeability of the leaves to polar materials. The split applications of bentazon increased 14C-bentazon accumulation in the leaf area above the treated spot 4 and 24 hours after treatment (Table 2). However, 5 days after 14C-bentazon application, the 14C had moved throughout the plant (Figure 2) consistent with greater reported efficacy of the split treatments (13). EPTC has been reported to reduce leaf surface wax of navy bean and increase the transpiration rate (23). However, preplant incorporation of a low rate of EPTC, 0.56 kg/ha, did not increase bentazon absorption by leaves (Table l). 65 Yellow nutsedge, 15.2 cm tall, grown under a dry soil regime absorbed less 14C-bentazon than plants grown in higher soil moisture regimes (Table 1) indicating that the reported loss of yellow nutsedge control under dry conditions (14) may be related to insufficient absorption of bentazon. Under water stress the leaf cuticle may be less hydrated and result in decreased absorption of polar materials (2). 14C-bentazon translocation in yellow nutsedge grown under dry soil conditions was less extensive compared to plants grown under higher soil moisture conditions, perhaps a reflection of decreased absorption (Table 2, Figure 2). Glyphosate absorption by yellow nutsedge 7.6 cm tall did not increase from 4 to 24 hours after the 14C-glyphosate application, indicating rapid initial absorption (Table 3). The yellow nutsedge 15.2 cm tall absorbed more 14C-glyphosate than the plants 7.6 cm tall. 14C-glyphosate was translocated rapidly both basipetally and acro- petally throughout yellow nutsedge plants 7.6 cm tall. However, even after 5 days no 14C was translocated to the parent tuber (Figure 3). 14C-glyphosate may be metabolized to non-toxic compoundscnrconjugated to other plant compounds before it can translocate into the tuber. This lack of translocation may explain why tubers of treated plants fail to rot as do tubers of bentazon treated plants. This is in contrast to purple nutsedge where 14C- glyphosate was translocated into tubers (24). 14C-glyphosate translocation was more extensive in the plants 7.6 cm tall than in the plants 15.2 cm tall (Figures 3 and 4), explaining the greater activity in yellow nutsedge 7.6 cm tall previously reported (13). Simi- lar observations have been made for control of purple nutsedge with glyphosate (24). 66 Ammonium sulfate increased absorption of 14C-glyphosate by yellow nutsedge 15.2 cm tall both 4 and 24 hours after treatment compared with 14C-glyphosate alone (Table 3). Ammonium sulfate may alter cuticular membrane permeability allowing more 14C-glyphosate to be absorbed. Ammonium sulfate has similarly been found to increase absorption of picloram by guava and dwarf bean (19). The combination with ammonium sulfate also resulted in a large in- crease in the amount of 14C-glyphosate found throughout the foliage (Table 4, Figure 4). This may have been a reflection of the increase in 14C-glyphosate absorption Shown in Table 3. Suwunnamek and Parker (16) concluded that ammonium sulfate had an effect on glyphosate action inside the purple nutsedge plant but not at the site of absorption, as ammonium sulfate applied 1 day after glyphosate still enhanced glyphosate activity on purple nutsedge. Ethephon significantly increased l4C-glyphosate absorption by yellow nutsedge 15.2 cm tall harvested 24 hours after treatment (Table 3). Ethephon has been reported (8) to reduce xylem tissue formation and in- crease the activity of 2,4,S-T ((2,4,5-trichlorophenoxy)acetic acid) on honey misquite (Prosopis glandulosa Torr.) control. The ethephon treatment also increased the accumulation of l4C-gly- phosate in the leaves above the treated area but had little effect on the distribution in the remainder of the plant 4 to 24 hours after treat- ment (Table 4). However, by 5 days after treatment basipetal transloca- tion of 14C was enhanced (Figure 4). Binning §£_al, (3) proposed that ethylene release from ethephon can alter the metabolic source-sink rela- tionship, as they fOund greater translocation of a dicamba (3,6-dichloro- g-anisic acid) in wild garlic when ethephon was applied 7 days before 67 the dicamba. The influence of ammonium sulfate and ethephon on l4C-glyphosate absorption and translocation by yellow nutsedge in this study are consis- tent with increased glyphosate activity by these combinations on yellow nutsedge control previously reported (15). Under high light intensity the plants absorbed a higher percent of the 14C-glyphosate applied than under low light intensity (Table 3). If uptake were an active process more energy would be available under the high light regime. Growing the yellow nutsedge plants under low light intensity reduced basipetal transport of the 14 C (Table 4). Since glyphosate is translo- cated together with photoassimilate in the phloem, a decrease in photo- assimilate accumulation and transport due to low light intensity should also result in decreased basipetal glyphosate movement. 10. 11. 12. 13. 68 Literature Cited Andersen, R.N., W.E. Lueschen, D.D. Warnes, and W.W. Nelson. 1974. Controlling broadleaf weeds in soybeans with bentazon in Minnesota. Weed Sci. 22:136-142. Ashton, F.M. and A.S. Crafts. 1973. Mode of action of herbicides. John Wiley and Sons, Inc. 504 pp. Binning, L.K., D. Penner, and W.F. Meggitt. 1971. The effect of 2-chloroethyl phosphonic acid on dicamba translocation in wild garlic. Weed Sci. 19:73-75. Boldt, P.F. and R.D. Sweet. 1974. Glyphosate studies on yellow nutsedge. Proc. Northeast. Weed Sci. Soc. 28:197-204. Kapusta, G. and J.A. Tweedy. 1973. Yellow nutsedge control in soybean. Res. Rpt. North Centr. Weed Contr. Conf. 30:108 and 110- 111. Ladlie, J.S., W.F. Meggitt, and R.C. Bond. 1973. Preplant incor- portated, preemergence and postemergence application on yellow nut- sedge in soybeans. Res. Rpt. North Centr. Weed Contr. Conf. 30:112- 113. Mahoney, M.D. and D. Penner. 1975. Bentazon translocation and metabolism in soybean and navy bean. Weed Sci. 23:265-271. Morey, P.R., R.E. Sosebee, and B.E. Dahl. 1976. Histological effects of ethephon and 2,4,5-T on misquite. Weed Sci. 24:292-297. Nalewaja, J.D. and K.A. Adamczewski. 1977. Uptake and transloca- tion of bentazon with additives. Weed Sci. 25:309-315. Schonherr, J. 1976. Water permeability of siolate cuticular mem- branes: the effect of pH and cation on diffusion, hydrodynamic permeability and size of polar pores in the cutin wax matrix. Panta 128:113-126. Sprankle, P., W.F. Meggitt, and D. Penner. 1975. Absorption, action and translocation of glyphosate. Weed Sci. 23:235-240. Stoller, E.W., L.M. Wax, and R.L. Matthiesen. 1975. Response of yellow nutsedge and soybeans to bentazon, glyphosate and perfluidone. Weed Sci. 23:215-221. Suwanketnikom, R., D. Penner, and W.F. Meggitt. 1978. Yellow nutsedge control with bentazon and glyphosate. Weed Sci. (Sub- mitted). 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 69 Suwanketnikom, R. and D. Penner. 1978. Environmental influence on yellow nutsedge control with bentazon and glyphosate. Weed Sci. (Submitted). Suwanketnikom, R. and D. Penner. 1978. Additives to increase bentazon and glyphosate activity on yellow nutsedge. Weed Sci. (Submitted). Suwunnamek, U. and C. Parker. 1975. Control of Cyperus rotundus with glyphosate: the influence of ammonium sulfate and other addi- tives. Weed Res. 15:13-19. Tweedy, J.A., G. Kapusta, and O. Kale. 1972. The effect of several herbicides on nutsedge control in soybeans. Proc. North Centr. Weed Contr. Conf. 27:28-29. Wang, C.H. and D.L. Willis. 1965. Radiotracer methodology in bio- logical science. Prentice-Hall Inc., Englewood Cliffs, NJ. 363 pp. Wilson, B.J. and R.K. Nishimoto. 1975. Ammonium sulfate enhance- ment of picloram activity and absorption. Weed Sci. 23:289-296. Wilson, B.J. and R.K. Nishimoto. 1975. Ammonium sulfate enhance- ment of picloram absorption by detached leaves. Weed Sci. 23:297-301. Wills, G.D. 1975. Taxonomy, morphology, anatomy, and composition of yellow nutsedge. Proc. North Centr. Weed Contr. Conf. 30:121- 124. Wills, G.D. 1976. Translocation of bentazon in soybeans and common cocklebur. Weed Sci. 24:536-540. Wyse, D.L., W.F. Meggitt, and D. Penner. 1976. The interaction of atrazine and EPTC on navy bean. Weed Sci. 24:4-10. Zandstra, B.H. and R.K. Nishimoto. 1977. Movement and activity of glyphosate in purple nutsedge. Weed Sci. 24:268-274. 70 Figure 1. Translocation of 14C-bentazon in yellow nutsedge 7.6 cm tall. Plants harvested (A) 1 day, (B) 5 days, and (C) 10 days after foliar application. Treated plants above (A-C) and correspond- ing radioautographs below (D-F). 71 Figure 2. 72 Translocation of 14C-bentazon in yellow nutsedge 15.2 cm tall harvested 5 days after foliar application. Treated plants above, (A) 14C-bentazon applied alone, (8) 14C-bentazon applied in combination with ammonium sulfate, (C) split appli- cations1 C-bentazon applied 5 days after application of 1.1 kg/ha of bentazon, and (D) 14C-bentazon applied when plants were grown in low soil moisture conditions. Corresponding radioautograph below (E-H). 73 74 Figure 3. Translocation of 14C-glyphosate in yellow nutsedge 7.6 cm tall. Treated plants above harvested (A) 1 day and (B) 5 days after feliar application. Corresponding radioautographs below (C-D). Figure 4. 76 Translocation of 14C-glyphosate in yellow nutsedge plants 15.2 cm tall receiving 14C-glyphosate applied (A) alone, (B) in com- bination with ethephon, and (C) in combination with ammonium sulfate 1 day after foliar application. Corresponding radio- autographs are (D-E). Plants receiving 14C-glyphosate applied (G) alone, (H) in combination with ethephon, and (I) in com- bination with ammonium sulfate 5 days after foliar application. 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Large amounts of 14C remained in the leaf area above the foliar treatment area 1 to 10 days after treatment. Less was present in the leaf section below the treatment area. Low amounts of 14C were found in other leaves, roots, rhizomes, and parent tubers. Most of the 14C found in the treated leaf was parent 14C-bentazon. Parent bentazon was also found in other leaves, roots, rhizomes and parent tubers. The metabolism in various plant parts was similar with up to nine 14C- metabolites separated. Five days after treatment the yellow nutsedge plants 7.6 cm tall and the plants 15.2 cm tall that had been treated with 9 kg/ha of ammonium sulfate had absorbed more 14C-bentazon than the 15.2 cm tall plants, but the percent of 14C remaining as unmetabolized bentazon did not differ. The increased activity of bentazon in combination with ammonium sulfate appears related to bentazon absorption and not an altered pattern of metabolism. 82 83 Introduction Yellow nutsedge, a serious weed problem in the United States (5,14), is propagated by both seeds and tubers, but propagation by tubers is the most important means of dissemination in cultivated cropland (1). Pre- emergence herbicides frequently fail to control yellow nutsedge as they may kill only the sprouting bud (16), but the tuber has several buds and each may be in a different stage of dormancy (9). Bentazon is a selective postemergence herbicide that has shown effi- cacy for yellow nutsedge control (4,10). Parent tubers of small yellow nutsedge plants may be killed (10,11) and there is evidence that 14C from foliarly applied 14C-bentazon translocates to the parent tubers of small plants (13). Addition of ammonium sulfate to the spray solution may increase effi- cacy of yellow nutsedge control with bentazon (12) by increasing absorp- tion and translocation of bentazon in yellow nutsedge (13). However, the effect of ammonium sulfate on bentazon metabolism in yellow nutsedge has not been determined. The objectives of this study were to determine: (a) the extent of bentazon metabolism in yellow nutsedge 7.6 cm tall, (b) whether parent bentazon or its metabolites translocated to other plant parts including the tubers, and (c) the effect of foliarly applied ammonium sulfate on bentazon metabolism. 84 Materials and Methods Yellow nutsedge tubers collected at East Lansing, Michigan were sprouted in control environmental chambers at 21 C. Plants with the same size shoots were placed three per cup in 294-ml cups and grown in modified Hoagland No. 1 solution. The plants were placed in the green- house at 25 :_3 C with supplemental fluorescent lighting to obtain a 14-h day length with 30.2 klux. When the plants reached the desired height, 7.5 or 15 cm tall, they were treated with 14C-bentazon. 14C-bentazon, labelled in the 10 position with a specific activity of 13.7 mC/mmole, was purified to 98%. A 5 pl drop containing 0.2 uCi of 14C-bentazon was applied to the second oldest leaf of each plant. The drop was placed in the middle of the leaf between two lanolin bars perpendicular to the length of the leaf. The plants were harvested 1, S, and 10 days after treatment. At harvest the roots, rhizomes, and tubers were washed in three successive water baths. The plants were dissected into the above treatment leaf area, below treatment leaf area, other leaves, roots, rhizomes, and tubers and then freeze-dried. For the comparison of metabolism in plants 7.6 and 15.2 cm tall with plants 15.2 cm tall receiving the combination of 9 kg/ha ammonium sulfate and 14C-bentazon, only the treated leaves were harvested and dissected into above treated area and below treated area and then freeze-dried. The treated spot on the leaf was discarded. In this study six plants were used per treatment. The procedures for studying metabolism were modified from the methods of Mahoney and Penner (6). For 14C extraction following treatment each plant part was cut into small pieces, pulverized with a mortar and pestle, 85 homogenized in 80% methanol, and the homogenate filtered through Whatman No. 1 filter paper under vacuum. The methanol-insoluble portion was com— busted by the method of Wang and Willis (15) and the radioactivity deter- mined by liquid scintillation spectrometry. The methanol-water-soluble fraction was evaporated to dryness in vacuo, resuspended in 15 m1 of 33% methanol, and partitioned against 15 ml benzene and then ethyl acetate three times each in S-ml fractions. All of the samples were then evaporated to dryness in vacuo and resuspended in 0.5 ml of their respective solvents. Fifty ul of each fraction was radioassayed, the remaining 450 pl were reduced to 50 ul by evaporation under N2 and spotted on 250 u thick silica gel F-254 thin layer chromatography plates. The plates were developed in a solvent system of chloroform:methanol (7:3, v/v) to 15 cm and radioauto- graphed. The 14C-labelled spots on the plates were removed and radio— assayed by liquid scintillation spectrometry. All data presented are the means of two experiments with two repli- cations each. Results and Discussion 14C—bentazon translocated from the treated leaf area to other leaves, roots and rhizomes, and parent tubers of yellow nutsedge 7.6 cm tall with- in 1 day, but most of the 14C-bentazon remained in the leaf area above the treated area even 5 and 10 days after treatment (Tables 1 and 2). 14C-bentazon in the leaf area above the treated spot was rapidly metabolized from 1 to 5 days after treatment (Table 2). The percentage of 14C found in the metabolite fraction increased while the percentage of unmetabolized bentazon decreased (Table 2). Little additional 86 metabolism occurred during the time period 5 to 10 days after treatment. In the leaf area below the treated spot the percentage of 14C found in the metabolites increased from 1 to 5 days after treatment but decreased from 5 to 10 days after treatment. The percentage of unmetabolized benta- zon also decreased from 1 to 5 days after treatment. A large percentage of the 14C was still found in the treated leaf (Table 2) 10 days after treatment. The metabolites or unmetabolized l4C-bentazon appeared mobile in the plant. Since less metabolites of 14C-bentazon were found in parent tubers (Tables 2 and 3) small but measurable amounts of unmetabolized 14C-bentazon were feund in the parent tuber and may have caused rot of the parent tuber as previously reported (11). The metabolites of benta- zon are 6 and 8 hydroxybentazon in wheat (8) or 6-(3-isopropyl-2,l,3- benzothiadizine-4-one-2,2-dioxide)-O-B-glucopyranoside in rice (7) neither are toxic. In yellow nutsedge 7.6 cm tall, only one metabolite was found in the ethyl acetate soluble fraction, but eight metabolites were found in the 80% methanol-soluble fraction (Table 3). Six metabolites were found in the leaf area above the treated spot 1 day after treatment, but by 5 and 10 days after treatment nine metabolites were found. These meta- bolites made up only a very low percentage of the total 14C (Table 3). In the leaf area below the treated spot the number and concentration of metabolites was similar to the area above the treated spot (Table 3). Similarly, in the other plant parts, the number of metabolites appeared to increase with time after treatment. The total amount of 14C-bentazon remaining in the treated leaf of plants 7.6, 15.2 cm tall, and plants 15.2 cm tall that received 9 kg/ha of ammonium sulfate was not different 1 day after treatment (Table 4). Five days after treatment the amount of 14C-bentazon in plants 7.6 cm 87 tall and plants 15.2 cm tall treated leaves with ammonium sulfate was greater than in plants 15.2 cm tall (Table 4). Therefore, it appears that 14C-bentazon was still being absorbed by the plants 7.6 cm tall and plants 15.2 cm tall treated with leaf ammonium sulfate up to 5 days after treatment. The percent of 14C that was unmetabolized bentazon was 71.1 to 75.9% 1 day after treatment and declined significantly 5 days after all treatments (Table 4). 14C-bentazon was metabolized faster in trifoliate leaves than uni- foliate leaves of navy bean and appeared related to the greater suscepti- bility of the unifoliate leaves (6). Although yellow nutsedge plants differing in height differed in susceptibility to bentazon (11), they did not differ in the rate of bentazon metabolism (Table 4). The ammonium sulfate treatment increased bentazon activity but did not increase the rate of metabolism. Analysis of the treated leaf shown no treatment differences in the percent of 14C remaining in the area above or below the treated area from 1 to 10 days after treatment (Table 5). Significantly less 14C was pre- sent below the treatment area compared to the area above the treated spot. In the treated leaf above the treatment area the rate of l4C-benta- zon metabolism to soluble 14C-metabolites in plants 7.6 cm tall and plants 15.2 cm tall with ammonium sulfate was greater than in plants 15.2 cm tall 5 days after treatment, the percent of soluble 14C-metabolites was not different 1 and 10 days after treatment (Table 6). The treatments did not differ in the percent of 14C found in the insoluble residue or in the material remaining at the origin of the TLC plates. Ten days after treatment the greatest percent of parent 14C-bentazon was found in the leaf area above the treated spot in the plants 7.6 cm tall. This 88 difference was not evident in the leaf section below the treatment area (Table 6). The ammonium sulfate treatment did not greatly enhance or decrease metabolism of bentazon in the treated leaf. TLC analysis of the soluble 14C further showed no effect of the ammonium sulfate on bentazon metabolism (Table 7). This ammonium sulfate appears to increase bentazon activity on yellow nutsedge by increasing bentazon absorption and possibly by interacting with bentazon at site of action such as uncoupling oxidative phosphorylation (3), nitrite accumulation (17) or inhibition of phytosynthesis (2). The stage of plant growth only slightly altered metabolism with less of the metabolite, Rf 0.15, and more of metabolite, Rf 0.28, occurring in the 7.6 cm tall yellow nutsedge leaf sections above the treated area, 10 and 5 days after treatment, respectively (Table 7). Numerous metabo- lites isolated 1 day after treatment from the treated leaf of 15.2 cm tall plants treated with both 14C-bentazon and ammonium sulfate were not pre- sent and detectable amounts in the yellow nutsedge 7.6 cm tall 1 day after treatment (Table 7). Although yellow nutsedge plants form numerous soluble metabolites from 14C-bentazon, the pattern of metabolism appears quite different from that of tolerant navy bean (Phaseolus vulgaris L.) and soybean (Glycine max (L.) Merr.) reported by Mahoney and Penner (6). 10. 11. 12. 13. 89 Literature Cited Bell, R.S., W.H. Lachman, E.M. Rahn, and R.D. Sweet. 1962. Life and history studies as related to weed control in the Northeast. 1. Nutgrass. Univ. of Rhode Island Agr. Exp. Sta. Bull. 363, 33 pp. Boger, P., B. Beese, and R. Miller. 1977. Long-term effects of herbicides on the photosynthetic apparatus: an investigation on bentazon inhibition. Weed Res. 17:61-67. Good, N.E. and S. Izawa. 1973. Uncoupling and energy transfer inhibition in photophosphoxylation. (In Current Topics in Bio- energetics. Edited by D.R. Sanadi.) Vol. 1, Academic Press, New York, 292 pp. Hendrick, L.W., M.A. Veenstra, and R.E. Ascheman. 1973. Canada thistle and yellow nutsedge control with split application of bentazon. Proc. North Centr. Weed Contr. Conf. 28:64. Jansen, L.L. 1971. Morphology and photoperiod response of yellow nutsedge. Weed Sci. 19:210-219. Mahoney, M.D. and D. Penner. 1975. Bentazon translocation and metabolism in soybean and navy bean. Weed Sci. 23:265-271. Mine, A., M. Miyakado, and S. Matsunaka. 1975. The mechanism of bentazon activity. Pest. Bioch. and Physi. 5:566-574. Ritzlaff, G. and R. Hamm. 1976. The relation between assimilation and the metabolism of bentazon in wheat plants. Weed Res. 16:263- 266. Stoller, E.W. 1975. Growth, development and physiology of yellow nutsedge. Proc. North Centr. Weed Contr. Conf. 30:124~125. Stoller, E.W., L.M. Wax, and R.L. Matthiesen. 1975. Response of yellow nutsedge and soybeans to bentazon, glyphosate and perfluidone. Weed Sci. 23:215-221. Suwanketnikom, R., D. Penner, and W.F. Meggitt. Yellow nutsedge control with bentazon and glyphosate. Weed Sci. (Submitted). Suwanketnikom, R. and D. Penner. Additives to increase bentazon and glyphosate activity on yellow nutsedge (Cyperus esculentus). Weed Sci. (Submitted). Suwanketnikom, R. and D. Penner. Influence of stage of growth, environmental factors, and additives on 14C-bentazon and l4C-glypho- sate absorption and translocation in yellow nutsedge (Cyperus esculentus). Weed Sci. (Submitted). 14. 15. 16. 17. 90 U.S. Department of Agriculture, Agricultural Research Service, Federal Extension Service, and Economic Research Service. 1968. Extent and cost of weed control with herbicides and an evaluation of important weeds, 1965. ARS 34-102, 85 pp. Wang, C.H. and D.L. Willis. 1965. Radiotracer methodology in biological science. Prentice—Hall Inc., Englewood Cliffs, NJ. 363 pp. Wax, L.M., E.W. Stoller, F.W. Slife, and R.N. Andersen. 1972. Yellow nutsedge control in soybeans. Weed Sci. 20:194-201. Weissman, 6.8. 1972. Influence of ammonium and nitrate nutrition on enzymatic activity in soybean and sunflower. 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