Miticide Efficacy Trial, 1989

Abstract

Abstract This experiment was conducted in a furrow-irrigated corn field at the Southwest Research-Extension Center. Treatments were arranged in a randomized complete block design with 4 replications. Plots were 4 rows wide (10 ft), 50 ft long with a 10 ft border of untreated corn on each side and a 10 ft alley between plots. Prior to treatment, 2 plants in each of the 2 center rows of each plot were flagged. The natural field population of spider mites was augmented by attaching small sections of corn leaves infested with BGM from a nearby corn field to these 4 flagged plants on 27 Jul. Pretreatment counts in the untreated check and Avid plots were made on 4 Aug. All other pre-treatment counts were made on 8 Aug by visually searching all leaves (whole plant) on the flagged plants for large (adult female) mites. Treatments were applied on 10 Aug (except Avid which was applied on 7 Aug) with a high clearance sprayer using a 10 ft boom with 3 nozzles directed at each row (one nozzle directly over the row and one on each side of the row on 18 inch drop hoses). The sprayer was calibrated to deliver 20 gal/acre using a ground speed of 2.3 mph and 30 psi. Posttreatment counts were made on 15 and 28 Aug by searching one half of every other leaf (one quarter plant) on the flagged plants. Mite counts were converted to mites/plant for analyses and presentation. Efficacy was evaluated by comparing the mean number of mites/plant among treatments using SAS Proc ANOVA and by comparing pretreatment means with post-treatment means using the Henderson and Tilton formula. The spider mite species composition which was present during the test was evaluated by collecting several mites from the flagged plants in each plot with a vacuum sampler on 18 Aug and mounting them on glass slides for microscopic determination of species.