EFFECT OF DROUGHT AND FORMULATION ON WILD OAT (AVENA-FATUA) CONTROL WITH IMAZAMETHABENZ AND FENOXAPROP

Experiments were conducted in the greenhouse to determine the effects of drought, rehydration and herbicide formulation on the phytotoxicity to wild oat of imazamethabenz and fenoxaprop. Under both well-watered and drought conditions, the activity of imazamethabenz with the liqui d concentrate formulation tended to be higher than the suspension conc entrate formulation, and the activity of the soluble powder formulatio n was enhanced by the surfactant Agral 90. Long-term drought did not r educe imazamethabenz phytotoxicity to wild oat with any formulations e xamined, whereas the phytotoxicity of three fenoxaprop formulations, f enoxaprop-ethyl, fenoxaprop-p-ethyl and fenoxaprop-p-ethyl plus safene r, was decreased by long-term drought, Fenoxaprop-ethyl activity was r educed by drought stress imposed before spraying, after spraying or, m ost significantly, both before and after spraying. The adverse effect of drought on fenoxaprop-ethyl activity was still evident even when da ily watering was resumed 8 to 48 h before spraying, although plants re hydrated in this way were more susceptible to fenoxaprop-ethyl than pl ants where rehydration was deferred until after spraying.