Control of Western Corn Rootworm Larvae, 1996

Insecticides were evaluated for rootworm larval suppression in two fields composed of Cozad silt loam soils. ‘DeKalb 580’ hybrid corn was ridge-planted in Field 1 on 1 May. At the time of planting, soil moisture was adequate for germination. Soil temperature at a depth of 5 cm was about 13°C. Four replicates of each treatment were applied at planting 5 X 40 ft plots in a RCB design. In Field 2, granular and liquid insecticides were applied to untreated strips immediately prior to cultivation on 13 Jun. The ‘Mycogen 6220’ hybrid plants were in the early whorl stage (V3 stage) of development at the time of application. Rootworm eggs began hatching about 6 Jun. The treatments were replicated four times in 10 X 35 ft plots arranged in a RCB design. The granular treatments were applied in a band over the whorl of the plants. Furadan 4F was broadcast over the top of the plants in a total volume of 25 gpa at 30 psi. Treatments in both fields were evaluated 12 Jul by rating washed roots of four plants from each replicate, using the 1 -6 Iowa State root damage rating scale.