Effect of Spinosad Formulations and Other Miticides on Twospotted Spider Mite, 1995

A trial was conducted in a commercial nursery with overhead irrigation in East Granby, CT. This experiment was conducted as a 10 (treatments) X 2 (one or two application) factorial RCB experiment (6 single-plant replicates) with spinosad (NAF-coded formulations), plus four positive controls and an untreated check. All surfaces of leaves were sprayed to run-off with a CO2-pressurized sprayer using 35 psi and a TeeJet 8002 flat fan nozzle. All plants were sprayed 1 Aug, with 95°F and 10 mph winds; the second treatment was 8 Aug, with 0-5-mph wind and 78°F. Leaf samples for mite counts were taken on 1 Aug (immediately prior to the first spray), and on 4, 7, 11, 14, and 21 Aug. One leaf was pulled from each plant, enclosed in aplastic bag, then immediately refrigerated (3-8 d). Mites on leaves were first evaluated under a dissecting microscope; when there were 30 or less mobile mites, then counts of mites were made directly. More heavily infested leaves were brushed onto an oiled glass plate and the number of mites estimated by subsampling the plate. Sections of a plate were counted until a minimum of 30 eggs or mobile stage mites were found. The number of mites on the entire plate was then determined by proportions. The leaf length and area were also recorded so that mites per unit area could be calculated. Data (mites per 10 cm2) required logarithmic transformation for analysis.