Corn Borer Insecticide Efficacy Trial, 1991

Abstract

Abstract This study was conducted in a furrow-irrigated corn field at the Southwest Research- Extension Center. Treatments were arranged in a randomized complete block design with four replications. Plots were 4 rows (10 ft) × 50 ft with a 10-ft border of untreated corn on each side and a 10-ft alley between plots. Simulated chemigation applications were made using 3 Delavan° 100/140 rain drop nozzles mounted on a high clearance sprayer at tassel height and centered between rows. This system was calibrated to deliver the equivalent of a 0.2-inch irrigation on the 2 center rows (5227 gal/acre). The standard treatments were applied with a high clearance sprayer using a 10-ft boom with 3 nozzles’directed at each row (1 nozzle directly over the row and 1 on each side of the row on 18-inch drop hoses). This system was calibrated to deliver 23.6 gal/acre using a ground speed of 2.4 mph and 31 psi. Winds were nearly calm and the temperature was 94°F at the time applications were made. The target application date for a single application was 24 Jul (approximately 50-75% oviposition) based on KSU’s predictive model backed by visual field scouting. Treatments were not applied, however, until 29 Jul (>75% oviposition) because of muddy field conditions. Comite° was applied to one set of plots to produce a reducedmite check in order to reduce mite pressure in order to help evaluate the effect of mites on the corn borer populations and corn yields. Corn borer counts were made 3-12 Sep by dissecting 15 consecutive corn plants from the center 2 rows (8 from the left row and 7 from the right row) in each plot. For each plant, the number of live second generation European corn borer larvae, the presence or absence of second generation corn borer tunneling, and the length of tunneling were recorded. The 15-plant totals for each of these categories were analyzed using SAS Proc GLM. Duncan’s Multiple Range Test was used to separate means. Results are reported as means per 15 plants, rounded to the nearest whole number.