Enhancing the margin of selectivity of RPA 201771 in Zea mays with antidotes

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-2914 8 and MON-13900 were the most effective of the five antidotes evaluated. R- 29148 applied at rates greater than or equal to 45 g ha(-1) provided excell ent protection against RPA 201772 injury and also prevented injury to Z. ma ys from diketonitrile, the active metabolite of RPA 201772. In laboratory s tudies, R-29148 did not alter absorption of C-14-RPA 201772 from soil; howe ver, R-29148 significantly enhanced the rate of RPA 201772 metabolism and i nactivation in Z. mays. The mixed function oxidase inhibitor piperonyl buto xide (PBO) increased RPA 201772 injury on all hybrids. These results demons trate 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 ox idative reactions may be involved in the metabolism of RPA 201772 in Z. may s.