EFFECT OF SIMULATED RAINFALL, INSECTICIDE FORMULATION, AND INSECTICIDE APPLICATION METHOD ON THE INTERACTION BETWEEN NICOSULFURON AND TERBUFOS IN CORN (ZEA-MAYS)

Applications of both terbufos and nicosulfuron can result in a synergistic interaction that injures corn. Field studies were conducted at two Illinois locations in 1991 to determine the effect of insecticide formulation and application method on the serverity of this interaction. Terbufos, applied to the soil at planting, interacted with nicosulfuron applied postemergence to injure corn and reduce grain yield. In-furrow-applied terbufos caused a more injurious interaction to corn than terbufos placed in a surface band; the 15G formulation was more injurious than the 20CR formulation. Simulated rainfall timing experiments were conducted in 1992 and 1993 by treating corn with terbufos 15G and terbufos 20CR and applying rainfall (3.8 cm) 1, 7, or 14 d before nicosulfuron application. No visual injury or yield reductions were noted in corn treated with nicosulfuron alone. Terbufos 15G caused greater corn injury than did terbufos 20CR at each rainfall timing when sprayed with nicosulfuron. Corn injury and subsequent grain yield that can result from the interaction between nicosulfuron and terbufos was greater when simulated rainfall occurred 1 and 7 d before nicosulfuron application than when rainfall occurred 14 d before application.