Impact of Spray Volume and Wetting Agent on Efficacy of Aerial Insecticide Applications to Man-Age First-Generation European Corn Borer Larvae in South Dakota, 1997

Abstract

Abstract Field plots were established in central South Dakota near Letcher to evaluate aerially applied insecticide treatments for control of first-generation ECB larvae. The field was planted on 11 May at a rate of 20,400 kernels per acre. The study was carried out to determine the impact of Silwet™ wetting agent and spray volume on the effectiveness of Warrior 1 EC insecticide. Pre-treatment counts revealed an average of 2 ECB larvae (ca. 50% each of 2nd- and 3rd-instars) existed per plant. A strip-plot ex-perimental design was used, and each strip contained 4 replicates. Sampling was conducted within a 32-row subplot (30.5 m by 100 m) for each treatment area. Insecticides were applied on 13 Jul at whorl (ca. 2 d before tasseling) stage in 15.2-m swaths at a speed of 110 mph using a Piper Brave aircraft. A Crop Hawk system was mounted on the aircraft to monitor and regulate spray flow through CP™ nozzles at 25 psi. Treatments consisted of Warrior 1 EC at 0.025 lb (AI)/acre in a spray volume of 2 or 5 gpa. Additionally, each of these spray volumes was evaluated with or without Silwet™ (wetting agent), and all were compared with an untreated control. Approximately one month after insecticide applications (8 Aug), 40 plants in each plot were randomly selected, split vertically and examined for ECB cavity (tunneling) damage. The number and length of ECB cavities were recorded and analyzed using the ANOVA procedure and means were compared by LSD.