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EFFECTS OF HERBICIDES ON NON-TARGET CROPS: DEVELOPMENT OF A POSSIBLE REPRODUCTIVE EFFECTS TEST
Citation:
Olszyk, D M., T G. Pfleeger, J S. Fletcher, E. S. Davis, AND M. Plocher. EFFECTS OF HERBICIDES ON NON-TARGET CROPS: DEVELOPMENT OF A POSSIBLE REPRODUCTIVE EFFECTS TEST. Presented at Crop Science Society of America annual meeting, Denver, CO, November 2-6, 2003.
Description:
Current phototoxicity tests for EPA registration of herbicides focus primarily on growth responses of plants exposed 14 days after emergence (DAE), which may not correspond to reproductive responses or to responses when plants are exposed at later, key developmental stages. We conducted preliminary experiments to determine potential reproductive responses (seed or tuber production) for crop seedlings exposed to simulated herbicide drift at 0, 0.001, 0.002, 0.01 and 0.1 and 1 x a field application rate of 52 g Ha-1 (active ingredient) of Oust? (sulfometuron). Herbicide applications were at flower initiation (soybean, pea) or tuber initiation (potato) as well as at 14 DAE. ?Stressland' soybeans, ?Dakota' peas and ?Russet Burbank' potatoes were grown in pots with a sandy loam soil in a greenhouse or outside in ambient air. Plant responses are reported for the minimum Oust? concentration producing a significant (p<0.05) reduction in yield (soybean seed dry weight, pea seed fresh weight, potato tuber fresh weight) vs. the 0 Oust? control. For soybeans, seed yield was reduced by 44% with 0.104 g Ha-1 Oust? at 14 DAE in the greenhouse; and by 98% with 0.52 g Ha-1 Oust? at flowering in the field. Pea seed yield was reduced by 100% with 0.052 g Ha- 1 Oust at 14 DAE in the field, and by 46% with 0.104 g Ha-1 Oust at flowering in the greenhouse. Potato tuber yield was reduced by 28% and 20% at 14 DAE and flowering, respectively, with 0.52 g Ha-1 Oust? in the greenhouse, and by 79% with 5.2 g Ha-1 Oust? at 14 DAE in the field. Thus, while reproductive responses appeared to be susceptible to fairly low levels of the herbicide Oust?, plant susceptibility differed with species, growth stage at herbicide exposure, and growth environment.