Efficacy and Mode of Action of CGA-154281, A Protectant for Corn (Zea mays) from Metolachlor Injury

Abstract

Greenhouse and field studies were conducted to determine the influence of herbicide rate, hybrid variability, and soil moisture on the effectiveness of CGA-154281 in protecting corn seedlings from metolachlor injury. High rates of metolachlor caused significant injury to seedlings of sensitive corn hybrids. However, with metolachlor plus CGA-154281, very few injury symptoms were observed, even with the 7.8 kg ha–1rate and the most sensitive hybrid. Corn seedlings were not injured by metolachlor plus CGA-154281 at the highest soil moisture level evaluated, whereas those treated with metolachlor alone showed 70% injury. Metolachlor injury increased as soil moisture content increased. In the greenhouse, CGA-154281 did not protect any of the eight weed species tested against injury by 2.2 kg ha–1metolachlor. In laboratory studies, CGA-154281 did not alter the absorption of14C-metolachlor during an 8-h period. Qualitative comparison of the metabolism of metolachlor in the presence or absence of the protectant indicated that metolachlor was metabolized to a more polar metabolite, believed to be a glutathione conjugate. However, CGA-154281 significantly enhanced the rate of metabolism of metolachlor in three of the four hybrids tested. Metolachlor metabolism activity may already have been functioning at a maximum level in the unaffected hybrid.