Imazethapyr Efficacy with Adjuvants and Environments

Abstract

Adjuvant effectiveness with imazethapyr for kochia control was generally methylated seed oil ≥ nonionic surfactant ≥ petroleum oil in the greenhouse experiments, and methylated seed oil ≥ petroleum oil nonionic surfactant in the field. Oil adjuvants were applied at 2.3 L ha-1and nonionic surfactants were applied at 0.25% (v/v) of spray volume. None of the adjuvants overcame imazethapyr reduced phytotoxicity caused by simulated rain soon after treatment, posttreatment cold (10 C), low soil moisture, or low soil nitrogen. However, kochia fresh weight reductions usually were the greatest when imazethapyr was applied with methylated seed oil, except in the case when soil had 80 ppm or less soil nitrogen. Kochia control with imazethapyr was enhanced the most by methylated seed oil followed by nonionic surfactant and petroleum oil regardless of relative humidity. High compared to low relative humidity tended to increase control for imazethapyr alone or with nonionic surfactant and decrease control for imazethapyr with oils. Kochia fresh weight reduction following imazethapyr treatment was greatest at 20 C, intermediate at 30 C and least at 10 C posttreatment when used with any of the adjuvants.