Influence of Chemigation Parameters on Fall Armyworm Control in Field Corn

Abstract

The application of pesticides in irrigation water (chemigation) is developing into a highly efficient and economical pest management strategy as the influence of application parameters are understood. In the current study, the effects of main-line water velocity, injection port direction, and sprinkler nozzle type were evaluated with two rates of chlorpyrifos to control fall armyworm larvae, Spodoptera frugiperda (J. E. Smith), in whorl-stage field corn grown under 0.6 ha center pivot irrigation systems. Chlorpyrifos injected into a main-line water velocity of 2.7 m/s generally gave as good or better fall armyworm control than when injected into a water velocity of 0.9 m/s regardless of sprinkler type. Upstream injection of chlorpyrifos formulated in non-emulsifiable oil resulted in better control of fall armyworm than did downstream injection. Chlorpyrifos applied with a 360@* spray sprinkler with coarse plates and nozzle orifice diam. between 3.6 and 9.5 mm at a main-line water velocity of 0.9 m/s gave the poorest fall armyworm control while an impact sprinkler gave the best control. The formulation droplet breakup in the main line and at the sprinkler were important factors in the distribution of insecticides to the target.