Insect Control with Insect Growth Regulators, 1988

Timing and rates of several insect growth regulators were evaluated for control of major apple pests and for their effect on phytophagous and phytoseiid mites. Sprays were applied by handgun operating at 200 psi to 2f-yr-old ‘Newtown’ trees. Treatments consisted of 4 single-tree replicates in a randomized block. Fungicides (Cyprex, Bayleton) were applied when necessary. Guthion cover sprays were timed according to CM development (see Washington State University Extension Bulletin 1072). The IGRs were applied from 150 to 250 degree-days earlier than Guthion to coincide with beginning and peak of egg laying. Dipel (Bacillus thuringieusis) + Guthion combination spray program was timed with Guthion sprays. Each material was applied in a program of 4 cover sprays. At mid-season (1 Aug) and at harvest (6 Oct), 100 apples/treatment (25/tree) were inspected for insect damage. In addition, leaves were sampled twice during the season to evaluate mite, WALH, and WTLM populations (100/leaves/treatment; 25/tree).