Insecticide Rescue Treatments for Control of First-Generation European Corn Borer in South Dakota, 1997

Abstract

Abstract Corn fields near New Holland and Letcher, South Dakota were used to evaluate planting-time and postemergence insecticides for controlling first-generation European corn borer, Ostrinia nubilalis Hubner, larvae. Preapplication counts (4 d before application) at Letcher indicated a uniform infestation of O. nubilalis larvae in 92.0% of plants sampled. Approximately 2.4 larvae (4.2, 62.5 and 33.3% were 1st, 2nd and 3rd instars, respectively) per plant were observed at this location. Similarly at New Holland a 90% infestation level (predominantly 1st and 2nd instars on the application date) existed, but the average number of larvae was estimated to be ~ 4-fold less than at Letcher). The at-planting-time treatment at New Holland occurred on 15 May and all whorl-treatments (approximately 1 week prior to tasseling) on 12 July (Letcher) and 15 July (New Holland). Insecticides were applied to single-row plots (16.4 cm by 30.5 m) in a randomized complete block design with 4 replicates. Granules were directed into corn plant’s whorl using a pneumatic applicator powered by a 3.5-horsepower engine mounted on a highboy. Noble metering units attached to a modified chain-driven apparatus regulated the amount of granules released into the pneumatic applicator. Liquid treatments were applied to corn plant whorls using a single-nozzle 3-gal. CO2-propelled backpack sprayer system. Approximately one month following insecticide applications (11 August), twenty corn stalks were randomly chosen from each plot. Each plant was split vertically and examined for O. nubilalis tunneling damage. The number and length of O. nubilalis cavities were analyzed using the ANOVA procedure with means being compared with the LSD.