Evaluation of Insecticides for Control of Larval European Corn Borer on Whorl-Stage Corn, 1997

Abstract

Abstract Experimental and labelled insecticides were evaluated for efficacy against larval ECB in whorl-stage field corn near Clay Center, NE. Experimental design was a RGB with four replicates. ‘Dekalb 641’ hybrid field corn was planted on 25 Apr into soybean stubble at a seeding rate of 29,900 plants/acre. Each plot consisted of a single row, 40 ft long with a 30-inch row spacing. Soil type was a Crete silt loam with a 0-1% slope. A CO2-pressurized back-pack sprayer mounted on the planter was used to apply liquid insecticides at planting. A TeeJet #250017 nozzle positioned between the disc openers was used to direct an in-furrow spray of 1.25 gpa at 8 psi (LP). Five plants per plot were artificially infested with 10 ECB egg masses each on 20 Jun. These plants were free of larval whorl damage prior to infestation based on visual inspection. Also, five naturally infested plants which exhibited active larval whorl feeding were marked at the time of artificial infestation. When the crop was in 8-leaf growth stage, the plants were artificially infested with egg masses in black-head stage on 21 Jun. All whorl treatments were applied on 26 Jun when crop was in 10-11-leaf growth stage. Granular insecticides were applied using the mason jar ‘shaker’ method (G). Liquid insecticides were broadcast over the top of the plant whorl with a CO2-pressurized backpack sprayer at 21 gpa at 30 psi (L). The stalks of both the artificial and naturally infested plants were split lengthwise and the total number of tunnels in the five plants per plot were recorded to evaluate ECB larval damage. The percent infestation at evaluation was determined by the number of plants with a minimum of 1 cavity. The artificially infested plants were evaluated on 21 Jul. The naturally infested plants were evaluated on 22 Jul and 28-29 Jul. Data were analyzed by ANOVA for RCB with mean separation using DMRT.