Evaluation of Granular Insecticides for Control of Lesser Cornstalk Borer in Irrigated and Unirrigated Tropical Corn, and in Two Levels of Soil Ph in Peanuts, 1990

Abstract

Abstract Granular treatments were applied to conventionally tilled and planted fields of tropical corn and peanuts in sandy loam soil at the Wiregrass Experiment Substation at Headland, Ala. Four replicates of 3 treatments and an untreated control were planted in a randomized complete block design for tropical corn, and 4 replicates of 4 treatments and an untreated control were planted in a randomized complete block design for peanuts. Treatments were applied to fields with a single-row, small-plot, granular applicator in a 7-inch band over the row. A liquid methyl parathion treatment was applied to the foliage in peanuts weekly for 4 consecutive wk using a boom sprayer with 1 hollow cone nozzle per row at 40 psi and delivering 8 gal/acre. Tropical corn plots were 12 rows wide (36-inch row spacing) × 60 ft long, and treatments were applied to both fields at emergence (13 Jun). One field was irrigated on 2 Jun (pre-planting) and at 15 and 47 DAT with a center pivot irrigation system. The other field was not irrigated. Granular treatments were applied to peanuts at flowering (27 Jun) on the two fields with differing pH. Plots were 6 rows wide (36-inch row spacing) and 50 ft long. A soil sample was taken at 0, 6, 13, 20, 34 and 50 DAT from tropical corn plots and at 0, 6, 13, 28 and 43 DAT in peanuts. Each soil sample (12-inch wide × 4-inch long × 1-inch deep) consisted of 3 subsamples from within each plot, and sampled areas were flagged to prevent resampling. Soil samples were returned to the laboratory and refrigerated until processed. Soil from each treatment was air dried to <1.0% moisture and placed in 1-oz plastic cups to a depth of 0.5 inch. Larvae were placed in cups and artificial insect diet was provided as a food source. Efficacy of pesticides was evaluated by exposing 27 first-instar lesser cornstalk borer larvae (3 replicates times 3 cups per replicate times 3 larvae per cup) to each treatment. At the end of 72 h exposure, living and dead insects were counted.