Nicosulfuron Resistance and Metabolism in Terbufos- and Naphthalic Anhydride-Treated Corn

Abstract

Synergistic interaction between the insecticide terbufos and the herbicide nicosulfuron may result in severe injury to corn. Greenhouse and laboratory experiments were conducted to determine if using the imidazolinone-resistant corn ‘Pioneer-3343 IR’ (P-3343 IR) or coating corn seeds with naphthalic anhydride (NA) would reduce herbicidal injury imposed by the nicosulfuron-terbufos interaction. Greenhouse experiments showed nicosulfuron-terbufos interactions resulting in herbicidal injury in both P-3343 IR and ‘DeKalb 689’ (D-689) corn varieties, but the D-689 was more sensitive than the P-3343 IR corn. The greenhouse experiments also demonstrated protection against the nicosulfuron-terbufos interaction by NA seed treatments. Studies with radiolabeled nicosulfuron showed that terbufos inhibited the metabolism of nicosulfuron, but pretreatment of D-689 and P-3343 IR corn seed with NA decreased the inhibition in excised corn leaves. The differences in sensitivity to nicosulfuron in the two corn varieties resulted in part from the differential metabolism and primarily from the differential sensitivity of the target enzyme, acetolactate synthase, to the herbicide.