CONTROL OF TWOSPOTTED SPIDER MITES AND EUROPEAN RED MITES ON TART CHERRY, 2005

The purpose of this study was to gain additional data on miticides for control of TSSM and ERM in tart cherries. The trial was conducted at the Northwest Michigan Horticulture Research Station in Traverse City, MI in cooperation with NWHRS farm manager, Bill Klein. One-tree plots were established in a mature block of wellpruned Montmorency tart cherry trees, and treatments then assigned in a RCB design with 4 replications. Most of the test materials were applied at threshold on 8 Jul, with an oil treatment added on 22 Jul. All applications were made with an FMC 1229 airblast sprayer calibrated to deliver 60 gpa at 3 mph. A pre-application count of TSSM was conducted on 6 Jul, and subsequent post-application evaluations were made on 15 Jul (7 days after application, DAA), 22 Jul (14 DAA), 29 Jul (21 DAA), 5 Aug (28 DAA), 12 Aug (35 DAA), 18 Aug (41 DAA), and 25 Aug (48 DAA). On each date, 25 randomly selected leaves were picked from each replicate, brought back to the lab, and passed through a mite-brushing machine. Motile forms of TSSM were then counted with the aid of a stereo microscope. Since ERM populations did not develop in this trial, no data are reported. All mite data are reported as the mean number of mites per leaf (Table 1), and % control (Table 2). Mean percent control was calculated using the Henderson-Tilton formula; % control = [1 – ((n control plot before treatment * n treated plot after )/( n control plot after treatment * n treated plot before ))]*100, and all data were analyzed using ANOVA and means separation by LSD at P ≤ 0.05.