Full-Season Insecticide Evaluations, 1989

Timing and rates of several experimental insecticides were evaluated for control of major apple pests and for their effect on phytophagous and predatory mites. Sprays were applied dilute by handgun operating at 200 psi to 22-yr-old Red Delicious' trees. Treatment rates given assume a spray volume of 400 gal/acre. Treatments consisted of 4 single-tree replicates in a randomized block. Trees were sprayed to runoff. Fungicides (Cyprex, Bayleton) were applied as needed to the whole test plot. Each treatment consisted of 4 cover sprays which were timed according to codling moth development (see Washington State University Extension Bulletin 1072). The degree-day (°D) figures in the tables are calculated from Biofix (1st CM catch in pheromone traps on 29 Apr). Insect growth regulator-type compounds were applied 100 to 150 °D (base 50°F) ahead of the standard Guthion program to coincide with the beginning and peak of egg-laying in each generation. Dipel (BT = Bacillus thuringiensis) and the Dipel-Guthion combination were applied at the same time as the Guthion sprays. At mid-season (11 Jul) and at harvest (28 Sep), 100 fruit/treatment (25/tree) were inspected for insect damage. In addition, leaves were sampled twice during the season to evaluate mite, WALH, and WTLM populations (25 leaves/tree; 100/treatment). Leaves were first scanned under a stereo microscope for WALH nymphs and WTLM mines. Then they were processed with a mite brushing machine to evaluate mite populations.