Effect of Rate and Timing of Biorational Materials for Control of First Generation White Apple Leafhopper Nymphs, 1995

Abstract

Abstract The test was conducted in a mature apple orchard (several strains of ‘Delicious’) on the grounds of the Tree Fruit Research & Extension Center, Wenatchee, WA. Treatments were replicated 4 times, with each replicate consisting of a single tree. The experimental design was a RCB, using pre-treatment WALH populations as the blocking factor. The experimental treatments (three types of horticultural mineral oil and Neemix, a neem product) were applied at various rates and timings. The standard timing was the presence of the first 4th instar nymphs (10 May). The end-of-generation timing (EOG) was the presence of the first adults (26 May). Pesticides were applied with a handgun sprayer to the point of drip. WALH phenology was determined by twice-weekly samples beginning in late bloom. A minimum of 100 nymphs was examined and categorized by instar. Presence of adults (EOG timing) was determined by examining the leaves in the field. Sprays were applied the day after the appropriate phenological stage was reached. Leafhopper populations were sampled ca. weekly by counting in situ all live nymphs on 20 leaves per tree, distributed throughout the tree canopy.