Effect of Larval Infestation Timing on Insecticidal Control of European Corn Borer in Minnesota Snap Bean, 1994

Abstract

This test was conducted on the University of Minnesota, Rosemount Experiment Station, in snap beans planted 2 Jun. Plots consisted of three 30 ft (9.14 m) rows on 30 inch (0.76 m) centers. Two untreated border rows and 7 ft (2.13 m) alleys separated the plots. Treatments were arranged in a split-plot design with four replications. Insecticide treatments were assigned to whole plots, while infestation timings consisted of single-row sub-plots within each whole plot. Treatments were applied 12 Jul using a moderate-clearance Spirit sprayer with 7 TX-10 hollowcone nozzles delivering 27 gpa (252.5 liter/ha) at 50 psi (3.51 kg/cm2) and 3 mph (4.8 km/hour). Plots were manually infested with ECB using a ‘bazooka’ applicator on 8, 15 and 19 Jul, corresponding to bud stage (72%), bloom (63%), and pod growth stages (75% at 0.5-3 inch length), respectively. On each infestation date, eleven consecutive plants in one row of each whole plot were infested with approximately 75 first-instar ECB larvae/plant. Infestations were designed to evaluate the activity of each material 4-d pretreatment, 3-d posttreatment and 7-d posttreatment. Beans were planted so that peak flowering would occur between the first and second generation ECB flights; feral ECB moth flights during this time were low. All treatments were evaluated 8 Aug by selecting five consecutive plants from the center of each infested row. Total pods, pods with feeding damage, stalk damage, and total ECB larvae were recorded.