Thiocarbamate and antidote effects on corn hybrids

Selected corn (Zea mays L.) hybrids were evaluated for their response to thiocarbamate herbicides at three Tennessee locations: the West Tennessee Experiment Station, Jackson; Milan Field Station, Milan; and the Plant Science Field Laboratory, Knoxville, during 1977. Nine corn hybrids selected for thiocarbamate herbicide response in 1976 were evaluated. The Jackson test was primarily an herbicide rate study of the susceptibility of the corn hybrids to EPTC (S-ethyl dipropylthiocarba-mate) or butylate (S-ethyl diisobutylthiocarbamate), in formulations with the herbicide antidote R-25788 (N,N-diallyl-2,2-dichloroacetamide) at 4.5 kg/ha, and 6.9 kg/ha. At Milan the response of corn to EPTC or butylate in formulations with the herbicide antidotes R-25788 or R-29148 (2,2,5 trimethyl-N-dichloroacetyloxazotidine) were compared. The Knoxville test compared the corn response to vernolate (S-propyl dipropylthiocarbamate) with both antidotes, also EPTC and R-12001 (S-isopropyl 5- ethyl-2-methyl-piperidine-1-carbothioate) in combination with R-25788. Data were obtained throughout the growing season on corn injury symptoms which included wrinkled or folded leaves, bent stalks, deformed husks, increased tillering, smut occurrence, and reduced grain yield. DeKalb XL55, treated with EPTC + R-25788, exhibited the largest number of injured plants, increased tillering, smut infestation and yield reduction at all locations. DeKalb XL55 treated with vernolate + R-29148 was injured with decreased yield. In Knoxville, vernolate with either antidote caused the most yield reduction. The grain yields of McNair X210, P.A.G. 644Wj Pioneer brand 3369A, and Pioneer brand 3147 were reduced when treated with vernolate + R-25788 while vernolate + R-29148 reduced the yield of DeKalb XL55 and P.A.G. 644W.