Effects of Pyrethroids and Miticides on Spider Mite, Southwestern Corn Borer and Predator Populations, 1982

Abstract

Abstract This experiment was conducted in a late-planted, flood-irrigated corn field in northern Grant Co, KS. Ten treatments were arranged in a randomized complete block design with 4 replications. Each plot was 3 m wide (4 rows) and 15.2 m long surrounded by a 3-m wide border of untreated corn. The chemical treatments were made twice, on Jul 30 (corn at 16-leaf stage) and Aug 10 (corn at tassel stage). These treatments coincided with the oviposition period of the Southwestern Corn Borer (SWCB) according to the predictions of the KSU model for SWCB development. Treatments were applied with a high clearance sprayer with 20 gal of water/acre at 30 psi of CO2pressure. Spider mites and spider mite predators were sampled Jul 29, Aug 5 and Aug 24. Counts were made by searching the leaves on 1 side of 2 plants in each of the 2 center rows to give 4 half-plant samples per plot. The plants were selected at random on the first sampling date and flagged so that the same plant could be counted on each sampling date. While visually searching the plants, records were made of adult female spider mites, active stages of the predator mite and Oriusnymphs. Representative samples of spider mites were mounted for microscopic examination and all were determined to be the Banks grass mite. Five consecutive corn stalks were split in each plot and the number of stalks with live SWCB larvae were recorded. Corn yields were determined by hand harvesting corn from 20 row-ft of each of the 2 center rows in each plot. Yields were corrected to 15.5% moisture.