4 ,,, . . . e *-,:& m$.. k::. , CONTENTS Page 3 4 5 INTRODUCTION............................................... MATERIALS AND METHODS..................................... RESULTS.................................................... Preplant Incorporated Applied Treatments ............. 5 Preemergence Applied Treatments.................... 9 Control of Selected Weed Species with Preemergence Applied Herbicides................. 13 SUMMARY. ............................................... Preplant Incorporated.............................. Preemergence .................................... 15 15 15 FIRST PRINTING 4M, NOVEMBER 1982 Information contained herein is available to all without regard to race, color, sex, or national origin. Performance of Preplant Incorporated and Preemergence Applied Herbicides for Weed Control in Cotton TED WHITWELL, R. HAROLD WALKER, and GLENN WEHTJE1,2 INTRODUCTION LITERATURE INDICATES that interest in agricultural weed control prior to 1500 AD was minimal. Weed control was either incidental to tillage for seedbed preparation or achieved by hand weeding. Often weeds were allowed to grow with the crop and separated out at harvest. A few inorganic herbicides became available during the 1800's and early 1900's. Research with organic herbicides began during the 1890's and accelerated in the early 1940's. 2,4-D was discovered and made available between 1942 and 1944; soon after, weed control through herbicides became an established agricultural practice. The number of herbicides in general use in the United States increased from approximately 15 in 1940, to 25 in 1950, to 100 in 1969, and 160 in 1982. Today, herbicides account for 60 to 70 percent of the multimillion dollar pesticide market in the United States. The Alabama Agricultural Experiment Station has evaluated hundreds of chemicals for weed control in cotton over the past 15 years. Several of these compounds have been successfully developed into marketable herbicides; however, the majority were proven unacceptable for one reason or another. The purpose of this bulletin is to provide results of a comparative evaluation that was made of the performance of AVAILABLE Scientist-Weed Control (joint employee with Cooperative Extension Service), Associate Professor, and Assistant Professor, Department of Agronomy and Soils. Research reported was initiated by Gale A. Buchanan, now Dean and Director, Alabama Agricultural Experiment Station. 2 The authors acknowledge the assistance of W. B. Webster and the late John Boseck, of the Tennessee Valley Substation, in this project. 'Respectively, ALABAMA AGRICULTURAL EXPERIMENT STATION preemergence and preplant incorporated applied herbicides used in cotton production in Alabama. MATERIALS AND METHODS Trials were conducted on a Decatur clay loam at the Tennessee Valley Substation, near Belle Mina, over an 8-year period. Weeds predominant in the area are listed in table 1. The test site was turned with a moldboard plow during the winter months; seedbeds were subsequently prepared in March and early April. Stoneville 213 cotton was planted between April 10 and April 20. Eleven herbicides registered for either preplant incorporated and/or preemergence application in cotton were evaluated for a minimum of 3 years each, table 2. Treatments were applied to plots four rows wide and 20 feet long, and replicated four times. Several rates of each herbicide, including the manufacturer's suggested range, were evaluated. All herbicides were broadcast applied in 15 to 18 gallons of water per acre via a tractor-mounted compressed air sprayer. Preplant incorporated treatments were incorporated TABLE 1. WEEDS PREVALENT AT THE TENNESSEE VALLEY SUBSTATION WHERE COTTON HERBICIDES WERE EVALUATED ON A DECATUR CLAY LOAM Weed Type Large crabgrass (Digitariasanguinalis) . ........ annual grass Goosegrass (Eleusine indica)..................annualgrass Fall panicum (Panicumdichotomiflorum) ....... annual grass Redroot pigweed (Amaranthusretroflexus) ...... annual small seeded broadleaf Pitted morningglory (Ipomoea lacunosa) ........ annual large seeded broadleaf annual large seeded broadleaf Prickly sida (Sida spinosa) .................... TABLE 2. HERBICIDES EVALUATED FOR WEED CONTROL IN COTTON AT THE TENNESSEE VALLEY SUBSTATION, 1972-80 Herbicide Chemical class Manufacturer Preplant incorporated treatments 1 U. S. Borax dinitroaniline Dinitramine (Cobex 2EC) ............. BASF Wyandotte dinitroaniline Fluchloralin (Basalin 4EC) ............ American Cyanamid Pendimethalin (Prowl 4EC). . ........... . . . . dinitroaniline 2 . . . . . . Ciba-Geigy . dinitroaniline Profluralin (Tolban 4EC) Elanco dinitroaniline Trifluralin (Treflan 4EC) .............. Preemergence treatments Shell triazine Cyanazine (Bladex 80WP) ............. DuPont substituted urea Diuron (Karmex 80WP) ............... Ciba-Geigy substituted urea Fluometuron (Cotoran 80WP) ......... Sandoz unclassified Norflurazon (Zorial 80WP) ............. 3M unclassified Perfluidone (Destun 50WP) ........... Ciba-Geigy Prometryn (Caparol 80WP) ........... triazine, S. Borax terminated the production of dinitramine in 1978. 2 Ciba-Geigy has terminated the production of profluralin; it will be available only until existing supplies are exhausted. 'U. PERFORMANCE OF HERBICIDES IN COTTON by tilling twice with a Lely-Rotera®, a horizontal action type tiller. Two of the four rows in each plot were cultivated. The remaining two rows were left uncultivated such that any weed control achieved would be due solely to the herbicide. Check plots without any weed control were included. Fertilization and insect control measures were determined by soil test recommendations and field scouting, respectively. Cotton injury and control of grasses and broadleaf weeds were visually rated 6 to 8 weeks, and again 3 months after application. Cotton was mechanically harvested two or three times and the cumulative yields reported in pounds of seed cotton per acre. RESULTS Preplant Incorporated Applied Treatments Dinitramine (Cobex 2EC). Excellent control of early season grasses was achieved in 3 out of 4 years with 0.5 pound per acre, the lowest rate tested, table 3. During the same years this TABLE 3. INFLUENCE OF DINITRAMINE (COBEX 2EC) APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF COTTON active/ac re Weed control' and injury ratings2 Grass control Broadleaf control Crop injury Late Early Late Late Early Early 90 99 98 0 98 100 99 0 50 75 70 0 85 96 100 0 84 96 100 0 86 80 93 0 38 60 95 0 0 0 10 0 0 20 24 0 0 14 53 0 0 10 23 0 0 0 0 0 0 8 47 0 0 11 23 0 0 0 0 0 Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 2,271 1,727 1,315 1,486 1,812 2,201 1,983 2,294 1,820 1,462 1,486 272 - 1973 0.50 .......... 96 1.00 .......... 99 2.00 .......... 100 Check ........ 0 1974 0.50 .......... 100 0.75 .......... 100 1.50 .......... 100 Check ........ .0 1975 0.50 .......... 100 0.75 .......... 99 1.50 .......... 100 Check ........ 0 1976 0.50 .......... 95 0.75 .......... 95 1.00 .......... 100 2.00 .......... 100 Check ........ 25 'Ratings of 80 or above 20-39 = none to slight, 25 56 0 5 0 840 794 38 94 25 0 0 1,307 1,315 100 93 38 10 0 1,245 1,346 100 96 64 44 0 747 560 0 25 0 0 0 1,221 723 are generally considered commercially acceptable. 40-69 = moderate, 70-99 = severe, 100 = death. ALABAMA AGRICULTURAL EXPERIMENT STATION rate generally provided satisfactory control of early season broadleaf and late season grass weeds. In 1974, comparable control of the late season grasses required 1.0 pound; late germinating broadleaf weeds were not controlled even with 2.0 pounds per acre, the highest rate tested. Substantial cotton injury frequently occurred with rates in excess of 0.75 pound per acre. Yields of uncultivated plots were generally lower than the cultivated plots, suggesting yield loss due to competition from uncontrolled broadleaf weeds. Fluchloralin (Basalin 4EC). Excellent early season grass control was obtained in 1974 and 1975 with rates as low as 0.75 pound per acre, table 4. The minimal rate needed to obtain satisfactory control of late germinating grasses was erratic, 0.75 pound in 1974 and 4.0 pounds in 1975. Control of early season broadleaf weeds could be consistently obtained with rates equal to, or greater than, 2.0 pounds. However, late germinating broadleaf weeds were not controlled with 4 pounds per acre, the highest rate tested. Substantial cotton injury was observed with 2.0- and 4.0-pound rates in 1974 and 1975, respectively. In general, yields for the cultivated plots were higher than the uncultivated plots. TABLE 4. INFLUENCE OF FLUCHLORALIN (BASALIN 4EC) APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF COTTON active/acre Weed control' and injury ratings 2 Grass control Broadleafcontrol Crop injury Early Late 98 100 100 100 0 20 0 70 100 0 Early 65 65 88 96 0 70 60 93 83 0 Late 0 0 0 36 0 0 0 78 68 0 Early 0 0 3 59 0 0 0 5 19 0 Late 0 0 10 43 0 0 0 0 0 0 Yield of seed cotton/acre Cult. Lb. 2,497 2,030 1,843 1,384 1,384 2,014 2,186 2,256 1,851 2,294 Uncult. Lb. 863 521 980 1,121 15 1,835 1,626 2,240 1,579 630 1974 0.75 .......... 1.00 .......... 2.00 .......... 4.00 .......... Check ........ 1975 0.75 .......... 1.00 .......... 2.00 .......... 4.00 .......... Check ........ 100 100 100 100 0 98 100 100 99 0 1976 6 778 303 1.50 .......... 100 100 28 0 0 98 75 81 0 0 5 840 646 3.00 .......... 0 0 0 708 0 Check ........ 44 0 0 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. PERFORMANCE OF HERBICIDES IN COTTON TABLE 5. INFLUENCE OF PENDIMETHALIN (PROWL 4EC) APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF COTTON Weed control' and injury ratings 2 Rate,/acb.re Grass control Broadleaf control Crop injury Early Late Early Late Early Late Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 1974 0.75 .......... 100 98 86 39 0 0 2,924 1,851 0 5 2,279 2,022 100 100 95 59 1.00 .......... 99 100 99 32 23 1,703 2,123 2.00 .......... 100 1,894 1,501 100 66 49 100 100 4.00 .......... 100 31 0 1,657 0 0 0 0 0 Check ........ 1975 20 66 0 0 0 2,294 0.75 .......... 96 23 0 0 2,326 96 43 63 1.00 .......... 93 35 0 0 2,271 2.00 .......... 100 93 2,224 99 93 5 0 4.00 .......... 100 95 Check ........ 0 0 0 0 0 0 1,921 1976 0 0 1,268 1,556 98 75 68 23 0.75 .......... 0 1,330 1,307 50 81 25 3 1.00 .......... 95 1,229 1,097 73 68 5 0 2.00 .......... 74 73 521 887 20 0 98 85 95 100 4.00 .......... 723 0 0 0 1,221 25 0 0 Check ........ 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. Pendimethalin (Prowl 4EC). Satisfactory control of early season grass weeds was achieved with 0.75 pound per acre, the lowest rate tested, table 5. In 1976, 2.0 pounds per acre resulted in unsatisfactory weed control, which appears to have been an anomalous situation since lower rates gave superior control. Late season grass control was excellent with all rates tested in 1974, with 2.0- and 4.0-pound rates in 1975, and with 4.0 pounds per acre in 1976. In all years of the study, acceptable early season broadleaf weed control was obtained with rates equal to, or greater than, 1.0 pound per acre. Rates of 2.0 to 4.0 pounds extended the control of broadleaf weeds into late in the season. However, these higher rates were marginal in terms of crop safety. Substantial cotton injury was observed at the 2.0- and 4.0-pound rates in 1974 and 1976, respectively. Uncultivated plot yields were generally lower than cultivated plot yields, suggesting that additional weed control measures may have been warranted. Trifluralin (Treflan 4EC). Early season grass weeds were controlled with 0.5 pound per acre, the lowest rate tested, table 6. Acceptable late season grass control was achieved in most years with rates as low as 1.0 pound. Treflan was less ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 6. INFLUENCE OF TRIFLURALIN (TREFLAN 4EC) APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF COTTON active/ac re Weed control' and injury ratings2 Grass control Broadleaf control Crop injury Early Late Early Late Early Late Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 1973 0.50 .......... 85 89 38 39 0 0 2,699 1,377 1.00 .......... 99 95 33 43 0 0 2,240 1,587 2.00 .......... 99 96 63 34 19 13 2,054 1,657 4.00 .......... 100 100 88 83 62 53 1,525 1,742 Check ........ 0 0 0 0 0 0 1,486 272 1974 25 0 0 3 0.75 .......... 100 98 1.00 .......... 100 100 64 0 0 9 20 2.00 .......... 100 99 88 0 23 4.00 .......... 100 100 93 13 45 53 Check ........ 0 0 0 0 0 0 1975 0.75 .......... 99 70 76 0 0 0 2,069 1,641 1.00 .......... 96 75 74 0 5 0 2,115 1,610 2.00 .......... 100 75 75 8 ' 0 0 2,155 1,820 4.00 .......... 100 48 91 46 56 9 1,315 1,175 Check ........ 0 0 0 0 0 0 2,294 1,073 1975 0.50 .......... 91 50 44 25 0 0 1,322 965 0.75 .......... 98 49 43 15 0 0 1,214 895 1.00 .......... 98 70 83 25 3 0 1,284 1,198 2.00 .......... 99 90 94 33 26 0 840 1,394 4.00 .......... 100 100 98 65 55 3 467 646 Check ........ 25 0 25 0 0 0 1,221 723 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. TABLE 7. INFLUENCE OF PROFLURALIN (TOLBAN EC) APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF COTTON Rate, lbWeed control' and injury ratings 2 Crop injury Grass control Broadleaf control active/acre Early Late Early Late Early Late 1974 0.75 .......... 1.00 .......... 2.00 .......... 4.00 .......... Check ......... 1975 0.75 ........... 1.00 ........... 2,00 .......... Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 2,357 575 2,100 816 1,952 1,034 1,781 1,065 1,384 15 2,201 2,186 2,077 100 100 100 100 0 98 95 99 95 98 100 98 0 50 50 50 19 29 58 93 0 63 63 86 , 0 0 0 0 0 0 0 0 0 0 0 19 0 0 0 0 0 5 0 17 0 0 0 0 1,844 1,729 1,743 4.00 ........... 99 97 93 63 36 6 1,548 1,774 Check ......... 0 0 0 0 0 0 2,294 630 1976 0.75 .......... 93 50 48 0 0 0 1,462 1,003 1.00 .......... 98 50 68 0 3 0 1,431 1,283 2.00 .......... 98 73 69 25 5 0 1,283 1,198 4.00 .......... 100 100 86 58 25 0 879 1,105 Check ......... 25 0 25 0 0 0 1,221 723 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. PERFORMANCE OF HERBICIDES IN COTTON effective in the control of broadleaf weeds. Acceptable control required rates equal to, or greater than, 1.0 pound per acre, and even then control was restricted to small seeded broadleaf weeds. Morningglory and prickly sida were not controlled at rates that were noninjurious to cotton. Substantial cotton injury resulted from rates of 2.0 pounds per acre and above. Cultivated plot yields were greater than uncultivated plot yields, reflecting the yield loss due to competition from uncontrolled broadleaf weeds. Profluralin (Tolban 4EC). Results were similar to trifluralin (Treflan) in that early season grass control was excellent even at rates as low as 0.5 pound per acre, table 7. Broadleaf weed control was poor. As with Treflan, only early season small seeded species could be controlled at rates that did not injure cotton (less than 4.0 pounds per acre). Preemergence Applied Treatments Cyanazine (Bladex 80WP). Excellent control of early season grass and small seeded broadleaf weeds was achieved at rates equal to, or greater than, 1.5 pounds per acre, table 8. However, control of late season grasses and broadleaf weeds was TABLE 8. INFLUENCE OF CYANAZINE (BLADEX 80OWP) APPLIED PREEMERGENCE WEED CONTROL, INJURY, AND COTTON YIELDS ON active/acre Weed control' and injury ratings 2 Crop injury Grass control Broadleaf control Yield of seed cotton/acre Early 1974 0.75 .......... 76 98 1.50 .......... 2.00 .......... 100 3.00 .......... 100 0 Check ........ 1975 1.25 .......... 75 0 Check ........ 1976 1.00 .......... 23 63 1.20 .......... 73 1.50 .......... 99 2.00 .......... 3.00 .......... 98 Check ........ 0 'Ratings of 80 or above 20-39 = none to slight, Late 10 33 43 71 0 0 0 Early 80 96 99 100 0 53 0 Late 18 59 81 68 0 0 0 Early 0 8 9 26 0 0 0 Late 0 0 0 10 0 0 0 Cult. Uncult. Lb. Lb. 2,403 2,738 2,349 2,007 2,403 1,906 2,294 1,252 2,131 2,240 1,727 280 - 4 801 13 48 0 8 25 50 0 6 3 755 50 78 0 11 0 934 50 83 0 4 0 848 25 93 0 35 4 537 48 0 0 0 0 1,097 are generally considered commercially acceptable. 40-69 = moderate, 70-99 = severe, 100 = death. 8 163 288 249 475 - 10 ALABAMA AGRICULTURAL EXPERIMENT STATION erratic even at the higher rates tested. The short soil persistence of this compound limits weed control to a limited period subsequent to application. Diuron (Karmex 80WP). Rates equal to, or greater than, 1.0 pound per acre provided satisfactory control of early season grass weeds, table 9. Control of late season grasses generally required 2.0 pounds, and even at this higher rate control was erratic. Only rates equal to, or greater than, 3.0 pounds per acre consistently provided acceptable control of late season broadleaf weeds. However, during one year these rates resulted in substantial crop injury. Uncultivated plots were generally lower in yield than cultivated plots. TABLE 9. INFLUENCE OF DIURON (KARMEX 80OWP) APPLIED PREEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF COTTON Rate, lb. active/acre Weed control' and injury ratings2 Crop injury Grass control Broadleaf control Early Late Early Late Early Late Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 1971 0 2,897 253 0 0 0 0 0.50 .......... 0 700 0 3,402 0 0 50 66 0 1.00 .......... 0 3,597 1,536 89 0 0 89 0 2.00 .......... 3,694 2,216 38 3 0 100 64 98 3.00 .......... 0 2,751 155 0 0 0 0 0 Check ........ 1972 95 70 0 0 4,006 3,376 1.00 .......... 98 49 0 4,045 3,881 100 100 0 100 99 2.00 .......... 3,835 3,920 100 100 96 11 0 3.00 .......... 100 3,780 462 0 0 0 0 0 0 Check ........ 1973 0 3,073 2,178 15 95 0 96 23 1.00 .......... 9 3,026 2,443 36 100 45 100 70 2.00 .......... 1,960 39 1,851 56 70 100 100 56 3.00 .......... 1,789 0 2,341 0 0 0 0 0 Check ........ 1975 2,333 0 0 78 65 93 86 1.00 .......... 0 0 2,170 89 100 96 100 2.00 .......... 2,326 0 0 0 0 0 0 Check .......... 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. Fluometuron (Cotoran 80WP). Acceptable control of early season grass and broadleaf weeds was achieved at rates equal to, or greater than, 1.5 pounds per acre, table 10. Control of late season grass weeds required at least 2.0 pounds, and even at this higher rate control was erratic. Cotton injury was minimal at rates less than 4 pounds per acre. At rates above 1.5 pounds, PERFORMANCE OF HERBICIDES IN COTTON TABLE 11 10. INFLUENCE OF FLUOMETURON (COTORAN 80WP) APPLIED PREEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF COTTON Rate,lb.re active/acre 1975 1.40 1.60 1.80 2.00 4.00 Weed controll and injury ratings 2 Crop injury Grass control Broadleaf control Early Late Early Late Early Late 65 71 69 78 100 0 91 .......... 97 .......... 90 .......... 96 .......... ............ 100 ........ - 96 98 93 98 100 0 70 94 88 89 100 0 15 0 0 0 11 0 9 0 0 0 3 0 Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 1,291 2,303 1,766 2,240 2,287 1,680 1,952 2,116 1,416 1,222 - Check 1976 545 1,384 0 3 59 90 0 61 1.00 .......... 0 1,276 1,027 0 83 95 0 80 1.50 .......... 949 1,190 3 75 0 96 0 91 2.00 .......... 1,595 1,291 0 0 95 100 46 100 3.00 .......... 0 1,369 0 0 0 0 0 0 Check ........ 1977 2,188 2,156 0 0 96 95 98 100 1.50 .......... 1,993 2,091 14 9 99 100 100 100 3.00 .......... 784 0 2,058 0 0 0 0 0 Check ........ 1978 2,287 2,482 0 0 87 59 94 95 1.00 .......... 0 2,156 2,222 0 87 99 96 .. 100 1.50 2,222 2,581 0 0 93 100 100 99 2.00 .......... 686 2,614 0 0 0 0 0 0 Check ........ 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. ......... TABLE 11. INFLUENCE OF NORFLURAZON (ZORIAL 8OWP) APPLIED PREEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF COTTON Rate, Weed controll and injury ratings 2 Crop injury Grass control Broadleaf control Gb. Early Late Early Late Early Late Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 3,461 2,862 2,162 3,539 3,445 3,204 3,185 280 2,403 1974 0 0 0 50 84 .99 1.00 .......... 0 0 70 98 96 100 1.50 .......... 0 0 100 100 100 100 3.00 .......... 0 10 100 100 100 100 4.00 .......... 0 0 0 0 0 0 Check ........ 1975 2,053 0 0 0 88 0 94 1.50 .......... 2,294 0 0 0 0 0 0 Check ......... 1976 887 1,245 8 4 45 70 93 1.00 ...........775 778 0 10 63 94 73 1.50 .......... 498 336 4 21 65 98 75 3.00 .......... 1,167 1,120 0 0 0 0 0 Check ........ 1977 2,124 1,928 0 0 91 95 100 100 1.50 .......... 1,830 0 2,222 0 84 95 97 .100 2.00 .......... 784 0 2,058 0 0 0 0 0 Check ........ 'Ratings of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69 = moderate, 70-99 = severe, 100 = death. 12 ALABAMA AGRICULTURAL EXPERIMENT STATION the uncultivated plot yields were similar to the cultivated yields, indicating effective weed control and little response to cultivation. Norflurazon (Zorial 80WP). Control of early and late season grasses was acceptable with 1.0 pound per acre, the lowest rate tested, table 11. Control of early season broadleaf weeds was achieved with rates equal to, or greater than, 1.5 pounds. Control of late season broadleaf weeds varied considerably between years. Cotton injury was similarly variable. Yields of the uncultivated plots were generally lower than the cultivated plot yields, suggesting that additional weed control may have been beneficial. Perfluidone (Destun 50WP). Early season grass control was excellent with 1.5 pounds per acre, the lowest rate tested, table 12. Acceptable control of late season grasses was TABLE 12. INFLUENCE OF PERFLUIDONE (DESTUN 50WP) APPLIED PREEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF COTTON active/acr, b. active/acre Weed controll and injury ratings 2 Grass control Broadleaf control Crop injury Early Late Early Late Early Late Yield of seed cotton/acre Cult. Lb. Uncult. Lb. 1974 1.50 .......... 95 66 81 33 3 8 2,038 1,361 2.00........... 98 73 65 19 10 14 1,540 754 2.50 .......... 100 96 88 43 6 6 2,007 1,384 3.00 .......... 99 98 90 24 14 25 1,836 1,081 6.00 .......... 100 91 99 83 26 40 1,703 1,657 Check......... 0 0 0 0 0 0 2,403 280 1975 1.50 .......... 74 59 48 0 0 0 1,571 622 2.00 .......... 80 43 34 0 16 10 1,229 459 3.00 .......... 88 76 71 23 23 18 1,213 887 4.00 .......... 91 73 81 45 28 28 957 731 Check ........ 0 0 0 0 0 0 2,326 624 1976 1.50 .......... 91 13 43 0 10 5 451 48 2.00 .......... 96 25 58 0 9 6 428 31 3.00 .......... 96 20 59 0 26 10 350 86 4.00 ..... ..... 98 25 89 0 20 16 381 140 Check ........ 0 0 0 0 0 0 1,167 16 1977 1.50 .......... .97 100 61 17 0 0 1,960 784 2.00 ........... 95 84 79 0 5 0 1,699 980 3.00 .......... 100 100 90 33 11 4 1,470 849 4.00 .......... 100 97 95 70 15 25 1,176 980 Check ......... 0 0 0 0 0 0 2,058 784 of 80 or above are generally considered commercially acceptable. 20-39 = none to slight, 40-69.= moderate, 70-99 = severe, 100 = death. 'Ratings PERFORMANCE OF HERBICIDES IN COTTON 13 achieved at rates equal to, or greater than, 2.5 pounds in all years except 1976. Control of early season broadleaf weeds was erratic. Acceptable control was achieved with only 1.5 pounds in 1974; whereas in 1975, 1976, and 1977, comparable control required 3.0 to 4.0 pounds. Late germinating broadleaf weeds could not be controlled at rates less than 6.0 pounds. This rate is impractical since cotton was consistently injured at rates in excess of 3.0 pounds per acre. Prometryn (Caparol 80WP). Control of early season grasses was excellent at all rates equal to, or greater than, 2.0 pounds per acre, table 13. Consistent control of the late season grasses and broadleaf weeds required rates of 3.0 pounds. Unfortunately, these rates resulted in crop injury during some of the test years. Uncultivated plot yields were generally lower than cultivated plots. TABLE 13 INFLUENCE OF PROMETRYN (CAPAROL 80WP) APPLIED PREEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF COTTON active, acre Weed control1 and injury ratings 2 Grass control Broadleaf control Crop injury Late Early Late Early Late Early 13 50 91 100 0 0 0 41 96 0 93 95 99 100 0 58 100 99 100 0 88 76 95 100 0 0 23 43 96 0 30 71 85 89 0 0 0 0 3 0 3 36 56 75 0 0 0 8 0 0 Yield of seed cotton/acre Cult. Uncult. Lb. Lb. 2,096 1,342 684 665 2,080 3,617 3,714 3,636 3,597 2,751 972 739 933 875 97 253 1,711 2,625 3,461 155 1970 1.0 ........... 85 2.0 ........... 91 3.0 ........... 99 6.0 ............ 100 Check ........ 1971 1.0 ........... 53 2.0 ......... .. 93 3.0 ........... .98 6.0 ............ 100 Check ........ 0 1972 2.0 ........... 100 3.0 ........... 100 6.0 ........... .100 Check ........ 0 of 80 or above 20-39 = none to slight, 'Ratings 95 100 99 0 0 4,013 3,881 99 98 99 0 0 3,982 3,819 100 100 100 3 0 3,726 3,625 0 0 0 0 0 3,780 462 are generally considered commercially acceptable. 40-69 = moderate, 70-99 severe, 100 =death. Control of Selected Weed Species with Preemergence Applied Herbicides Perfluidone, fluometuron, and norflurazon provided excellent control of early season crabgrass, table 14. However, all herbicides were ineffective on late germinating crabgrass. 14 ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 14. LOWEST RATE REQUIRED OF EACH HERBICIDE TO CONTROL EARLY AND LATE SEASON GRASS AND BROADLEAF WEEDS Herbicide and year Lowest rate required to control Broadleaf weeds Grass weeds Late Late Early Early Lb. Lb. Lb. Lb. PREPLANT INCORPORATED Dinitramine (Cobex 2EC) 0.50 0.50 1973 ..................... .500 .50.50 1974 ..................... .50 1975 ..................... 1.00 .50 1976 ..................... Fluchloralin (Basalin 4EC) .72.00 .75 1974 ..................... 4.00 .75 1975 ..................... 1.50 1.50 1976 .................... Pendimethalin (Prowl 4EC) .75 .75 1974 ..................... 2.00 .75 1975 ..................... 4.00 .75 1976 ..................... Profluralin (Tolban 4EC) .75 .75 1974 ..................... .75 4.00 1975 ..................... 4.00 .75 1976 .................... Trifluralin (Treflan 4EC) .50 .54.00 1973 ..................... .75 :.. .50 1974 .................. 1 .50 1975 ..................... .50 2.00 1976 ..................... PREEMERGENCE Cyanazine (Bladex 80WP) .......... 1974 ........... 1976 1971 ..................... ..................... 2.00 1 .50 .75 2.00 3.00 2.00 1.00 4.00 2.00 4.00 2.00 4.00 1.00 - - 2.00 4.00 4.00 1 1 4.00 1 1 1.50 2.00 2.001 1 _1 .75 2.00 2.00 - 1 Diuron (Karmex 80WP) 1.00 2.00 1972 ...................... 1 1.00 1973 ....................... 1.00 1.00 1975 ..................... Fluometuron (Cotoran 80WP) 4.00 1.40 1975 ..................... 1 1.50 1976 ..................... 1.50 1 1977....................... 1.00 1.50 1978 ..................... Norflurazon (Zorial 80WP) 1.00 1.00 1974 ..................... 1.00 2 1976 ..................... 1.50 1.50 1977 ...................... Perfluidone (Destun 50WP) 2.50 1.50 1974 ...................... - 1 2.00 1975 ..................... _ 1.50 1976 ..................... 1.50 1.50 1977 ..................... Prometryn (Caparol 80WP) 3.00 1.00 1970 ..................... 6.00 2.00 1971 ..................... 2.00 2.00 1972 ..................... 1Acceptable control was not achieved with the rates tested. 2 Data not taken. 1.00 1.00 2.00 1.40 1.00 1.50 1.00 1.50 1.50 1.50 1.50 4.00 4.00 3.00 1.00 2.00 2.00 2.00 1 2.00 1.60 1.50 1.50 1.00 3.00 1 1.50 6.00 1 1.00 6.00 2.00 PERFORMANCE OF HERBICIDES IN COTTON 15 Cyanazine, perfluidone, and norflurazon were highly effective for early season goosegrass control. All evaluated herbicides were effective for early season fall panicum control. Perfluidone, fluometuron, and norflurazon were highly effective in early season pigweed control, but only fluometuron provided excellent late season pigweed control. Fluometuron was the only herbicide that provided acceptable early and late morningglory control. All herbicides provided acceptable control of early season prickly sida; however, only fluometuron provided acceptable late season control. SUMMARY Preplant Incorporated All preplant incorporated herbicides provided excellent control of early season grasses at all rates evaluated, table 14. In addition, trifluralin and dinitramine provided excellent late season grass control at rates of 1.0 pound or more. Fluchloralin, pendimethalin, and profluralin were generally effective in controlling later germinating grasses at rates above 2.0 pounds per acre. Dinitramine in 3 out of 4 years provided excellent control of early season broadleaf weeds at 0.50 pound. Pendimethalin also provided effective early season broadleaf control above 0.75 pound. At rates above 2.0 pounds, trifluralin and fluchloralin were also effective on early season broadleaf weeds. Comparable control with profluralin generally required higher rates. In 2 out of 3 years, only the high rate (4.0 pounds) of pendimethalin provided effective late season broadleaf weed control. It is important to note that all rates were equally effective on pigweeds and other small seeded broadleaf weeds. Preemergence Cotton stands were not consistently affected with any of the herbicides evaluated when used at the labeled rates. High rates did reduce stands in certain years. Yields from cultivated plots were reduced at these high rates. The only herbicide to consistently reduce yields at all rates was perfluidone. Acceptable control of early season grasses was consistently achieved with a minimal rate of all preemergence herbicides tested. Invariably, higher rates were required to control late season grasses. With the exception of perfluidone, all her- 0) TABLE 15. EFFICACY OF SELECTED PREEMERGENCE HERBICIDES ON SIX WEED SPECIES Herbicide, rate/acre Cyanazine, 1.5 lb. (Bladex 80WP) .... Crabgrass Early Late 772 33 Goosegrass Early Late 82 - Percent control by weed species' Fall panicum Pigweed Morningglory Early Late Early Late Early Late 85 74 16 43 24 Prickly sida Early Late 82 28 C 3 Perfluidone, 3.0 lb. (Destun 50 WP) .. 97 41 Fluometuron, 1.5 lb. (Cotoran 80WP) . 96 54 Norflurazon, 1.5 lb. (Zorial 80WP) .... 97 33 Check .............................. 0 'Average for 1975, 1976, and 1977. 20 = no control or injury; 100 = complete control.M 97 73 100 0 - - 97 98 100 0 83 0 84 100 99 0 50 99 61 0 74 94 78 0 8 80 53 0 80 98 97 0 7 80 69 0 p c c i- m x m z -1 -I -I m 0 z PERFORMANCE OF HERBICIDES IN COTTON -17 bicides at rates of 1 to 2 pounds per acre provided acceptable control of early season broadleaf weeds. In 2 out of 4 years, 4.0 pounds of perfluidone was required for acceptable control. Fluometuron and norflurazon were the most effective preemergence treatments available for the control of late season broadleaf weeds. Although results were variable, both of these herbicides frequently provided acceptable control with 1.5 to 3.0 pounds. Diuron and prometryn also provided acceptable control if high rates were used. However, these rates were often injurious to the cotton. Visual ratings averaged for 1975-77 for six weed species indicated that fluometuron at the 1.5-pound rate provided effective early and late control of all weeds except late crabgrass, Table 15. Perfluidone at 3.0 pounds and norflurazon at 1.5 pounds per acre provided effective early season control of goosegrass, fall panicum, and prickly sida. Ineffective late season weed control was observed with cyanazine. Only the highest rate of all the herbicides evaluated consistently reduced cultivated yields when compared to the check. With the exception of fluometuron in some years, all uncultivated yields were consistently lower than cultivated plots, indicating that a single herbicide application did not provide season-long weed control. The preplant incorporated and preemergence applied herbicides discussed in this publication provide acceptable control of a number of grass and broadleaf weeds without substantial damage to cotton. A combination of cultivation and herbicides is an effective, economical approach for weed control in cotton. AUBLRN UNIVERSITY W\ith an agricultural research unit in evt2- thimajr s il area, Atuhrn t ix-ersitxt serves the needs of hield crop, liv esto)ck forestry, and ho)rticclt c ral prt tclucers in each region in Alabamlla. Lverx citi ten f the State has a O O :;r, i 0, stake in this research program, since anx advantage fi-( )l nex andtc iMore ec'c( nom- ical wxax s Of prcIucing aInd handling farm prodciCics directly benefits the consnling public. ® Main Agricultural Experiment Station, Auburn. s E. V. Smith Research Center, Shorter. Tennessee Valley Substation, Belle Mina Sand Mountain Substation, Crossville North Alabama Horticulture Substation, Cullman Upper Coastal Plain Substation. Winfield. Forestry Unit, Fayette County Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County Piedmont Substation, Camp Hill Plant Breeding Unit, Tallassee Forestry Unit, Autauga County Prattville Experiment Field, Prattville Black Belt Substation, Marion Junction The Turnipseed-Ikenberry Place, Union Springs Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County Monroeville Experiment Field, Monroeville Wiregrass Substation, Headland Brewton Experiment Field. Brewton Solon Dixon Forestry Education Center, Covington and Escambia counties 20. Ornamental Horticulture Field Station, Spring Hill 21. Gulf Coast Substation. Fairhope 1. 2. 3. 4. 5. 6. 7. 8 9 10. 11. 12. 13. 14 15 16. 17 18 19