The antidotes dichlormid, MON-4660, CGA-154281, R-29148, and MON-13900 were tested in the greenhouse to protect Zea mays L. (corn) against RPA 201772 injury. High rates of RPA 201772 injured four Z. mays hybrids > 30%. R-29148 and MON-13900 were the most effective of the five antidotes evaluated. R-29148 applied at rates ⩾ 45 g ha−1 provided excellent protection against RPA 201772 injury and also prevented injury to Z. mays from diketonitrile, the active metabolite of RPA 201772. In laboratory studies, R-29148 did not alter absorption of 14C-RPA 201772 from soil; however, R-29148 significantly enhanced the rate of RPA 201772 metabolism and inactivation in Z. mays. The mixed function oxidase inhibitor piperonyl butoxide (PBO) increased RPA 201772 injury on all hybrids. These results demonstrate that Z. mays tolerance to RPA 201772 can be enhanced with the use of antidotes such as R-29148 and MON-13900, that R-29148 protects Z. mays from RPA 201772 and diketonitrile by the enhancement of metabolism, and that oxidative reactions may be involved in the metabolism of RPA 201772 in Z. mays.

Benoxacor, CGA-185072, and MON-13900 were evaluated in laboratory studies as safeners to reduce injury caused by primisulfuron when corn has been previously treated with terbufos. Without safeners, shoot length was reduced 30% when primisulfuron (78 gm ha-1) followed terbufos (2.6 kg ha-1) applications. Stunting was significantly reduced by preemergence applications of CGA-185072 and MON-13900 at 200 g ai ha-1; however, shoot length was still reduced by 21 and 12%, respectively. Benoxacor did not reduce primisulfuron injury in corn previously treated with terbufos. Safening by CGA-185072 and MON-13900 was not due to reduced primisulfuron uptake or altered translocation. MON-13900 was further evaluated for its effects on primisulfuron metabolism. MON-13900 increased primisulfuron metabolism in terbufos-treated shoots by more than 50%. This increase in metabolism appears to be the mechanism of safening by MON-13900.