Efficacy of Miticides Against Corn Spider Mites, 1986, #2

Abstract

Abstract This experiment was conducted in Finney County, KS in a field of flood irrigated corn where the natural mite populations were augmented with twospotted spider mites. Thirteen treatments were arranged in a randomized complete block design with 4 replications. The plots were 4 rows wide × 10 ft, 50 ft long, and surrounded by 10 ft borders of untreated corn. Prior to treatment, 4 plants in each plot were selected from the center 2 rows and flagged. The natural mite population was augmented by attaching leaves infested with twospotted spider mites from a greenhouse colony. Treatments were applied with a high clearance sprayer using a 10 ft boom with 3 nozzles directed at each row (1 nozzle directly over the row and 1 on each side of the row on 18 inch drop hoses). The sprayer was calibrated to deliver 20 gpa of water with 30 psi of CO2 pressure. The plots were treated on 9 Aug. Spider mite counts were made from the flagged plants by searching every other leaf on each plant for large mites (primarily the adult females). Pretreatment counts were made on 29 Jul and the posttreatment counts were made on 14 Aug. The percentage of twospotted spider mites present in each plot was determined by collecting 20 to 40 mites from the flagged plants in 2 of the replicates with a small vacuum sampler and mounting them for microscopic determination of mite species.