Control of Western Corn Rootworm Larvae in West Central Nebraska, 1993

Abstract

Abstract Insecticides were applied to suppress larval rootworm populations in 2 fields in westcentral NE. Both fields were located at the University of Nebraska West Central Research and Extension Center and were composed of Cozad silt loam soils. Hybrid field corn was ridge-planted in Field 1 with a John Deere Max-emerge planter, to a non-tilled seed bed on 20 May. At the time of planting, soil moisture was adequate for germination and the soil temperature was about 18° C. Several insecticides were applied at planting to a single row 145 m in length with insecticide boxes attached to the planter. Four replications of each treatment were arranged in a RCBD. T-band applications were made by applying a 7 inch band of insecticide in front of the press wheel. In-furrow applications were made by applying insecticide directly into the seed furrow. Field 2 was ridge-planted to ‘BoJac 520’ and ‘BoJac x438’ hybrid field corn with a John Deere Max-emerge planter, in a non-tilled seed bed on 6 May. At the time of planting, soil moisture was adequate for germination and the soil temperature was about 13° C. With the exception of 4 field length strips, 12 rows in width, Lorsban 15G was applied at planting with insecticide boxes on the planter at a rate of 836 g (AI)/ha. Granular and liquid insecticides were applied to untreated strips in Field 2 immediately prior to cultivation on 25 Jun. The corn plants were in the early whorl stage (growth stage 2) of development at the time of application. The granular treatments were applied over the whorl of the plants, on 10 m of a single row, with insecticide boxes attached to a tool bar. Furadan 4F was applied to 10 × 4 m plots in Field 2 either broadcast or in 7 inch bands to the base of the plants. All liquid treatments were applied in a total volume of 120 liters/ha at 206,786 Pa (30 psi). All treatments were replicated 4 times and arranged in a RCBD. Two blocks of treatments were applied to ‘BoJac 520’ hybrid field corn plants and 2 blocks of treatments were applied to ‘BoJac X438’ hybrid field corn plants. Treatments in both fields were evaluated 22 Jul by rating washed roots, using the 1-6 Iowa Root Damage Rating Scale, of 4 plants from each replicate. Data from each field were analyzed separately with analysis of variance and an LSD test was used for mean separation.