Spruce Spider Mite Control with Insecticidal Soap and Conventional Pesticides on Fraser Fir in Centre County, 1987

Eighteen treatments were evaluated to control spruce spider mites on heavily infested 5-6-ft Fraser fir Christmas trees. Each treatment was applied to 4-tree replicates. Foliar sprays were applied by using a CO2 sprayer with one 8004VS Teejet nozzle operating at 28 psi and mounted on the end of a 24-inch boom. 940 ml of each treatment was applied to each replicate. Treatments were applied 13 May under clear, sunny skies. The air temperature was 85°F and 70% RH. Samples consisted of randomly removing four 4-inch twigs from each replicate. The twigs were placed in plastic bags and transported in an ice cooler to the laboratory. Samples from each replicate were then passed through a mite brush, and the number of viable spruce spider mite life stages (larvae, nymphs, adults) collected on a 5-inch sampling disk positioned directly beneath the brushes was counted with a stereo dissecting microscope. Posttreatment samples were collected 29 May and 11 Jun.