Evaluation of Microbial and Conventional Insecticides for Control of Larval European Corn Borer on Whorl Stage Corn, Clay Center, Ne, 1995
Abstract Bacillus thuringiensis formulations and conventional insecticides were evaluated for efficacy against larval ECB in whorl stage field corn. All plots were planted without soil insecticide on 16 May. The experimental design was a RCB with 4 replicates. Each plot consisted of a single row, 40 ft long with a 30-inch row spacing. Plots were artificially infested with black-head stage ECB egg masses. The egg masses were deposited on wax paper discs, precounted in the laboratory and placed in the whorl of the infested plants on 30 Jun and 9 Jul. Crop growth stage was 37 and 57 inches extended leaf height, respectively. The same 5 plants in each treatment replicate were infested with 10 egg masses per infestation date. All granular insecticides were applied on 13 Jul. Environmental conditions were: air temperature, 81°F; wind direction and speed, west (250°) at 7 mph; relative humidity, 53%; and crop growth stage, 63 inches extended leaf height. A 10-inch Almaco smooth belt cone rear mounted on a Hahn Hi-Boy was used to apply preweighed amounts of the granular insecticides over the top of the plant whorls (G). Liquid insecticides were applied on 15 Jul. Environmental conditions were: air temperature, 74°F; wind direction and speed, east (80°) at 5 mph; relative humidity, 76%; and crop growth stage, 67 inches extended leaf height. A CO2 pressurized backpack sprayer at 30 psi was used to apply a band application over the top of the whorl (total spray volume = 1050 ml/plot) of premeasured amounts of the liquid insecticides (L). All infested plants were evaluated for ECB larval feeding damage on 14-15 Aug. The stalks of the infested plants were split lengthwise and the accumulated length and number of cavities in the 5 plants per treatment replicate were used to evaluate ECB larval damage. The percent infestation at evaluation was determined by the plants with a minimum of 1 cavity per treatment replicate. Data were analyzed by ANOVA for RCB with mean separation using DMRT.