Corn Rootworm Control, 1988

Abstract

Abstract Planting-time (Test 1) and first-cultivation (Test 2) soil insecticide trials were conducted at Mead, Nebr., and in Clay County, Nebr. The Mead plots were in trap crop (no insecticide) during 1987 and had been used periodically for multiclass soil insecticide trials for at least 10 yr. The Clay County plots were in trap crop during 1987, were used for multiclass soil insecticide trials in 1981-1982 and 1985, and were insecticide free in 1983-1984 and 1986-1987. The soil at each site was a silty clay loam. The experimental design for each test was a randomized complete block with 4 replicates. Each replication consisted of single-row treatments that were 35 (Mead) or 40 ft (Clay) long and 30 inches apart. Equipment for Test 1 consisted of modified V-belt seeders mounted on a planter. Preweighed amounts of insecticide granules were placed on the V-belts and directed into the seed furrow or banded over the row in front of the press wheel. Noble granular insecticide metering units mounted on a hand-powered bicycle applicator were used to apply soil insecticides in Test 2. Granules were banded directly over the plant whorl and then immediately incorporated by the cultivator. The Mead and Clay trials were planted 6 May and 21 Apr, respectively. Test 1 treatments were applied 2 Jun (Mead) and 3 Jun (Clay). Soil moisture conditions were excellent when insecticides were applied except for Test 2 at Clay; insecticides were placed into a fairly dry seed bed. Initial egg hatch was detected 1 Jun at Mead. Stand counts were taken on 16 May (Clay) and 27 May (Mead). Feeding damage was evaluated 7-11 Jul at Mead and 13 Jul at Clay by digging 5 roots from each treatment row and rating the damage according to the Iowa 1-6 scale (1, no feeding; 6, 3 or more nodes of roots completely destroyed). Data were subjected to ANOVA.