Second-Generation Walh Insecticide Experiment, 1987

This test was conducted in a 7-yr-old orchard with under-tree irrigation. The experimental design was a randomzied complete block with 4 single-tree replicates/treatment. Materials were applied to the point of drip with a handgun sprayer operated at 400-500 psi. Rates were based on a dilute application of 400 gal/acre. Treatments designated as early timing (E) were applied on 28 Jul; those marked standard (S) were applied on 12 Aug. Early sprays were timed shortly after the second-generation nymphs hatched. The standard timing coincided with the first appearance of fourth-instar WALH. WALH densities were determined by counting nymphs on 20 leaves/tree showing visible injury on the upper surface. Counts were made at weekly intervals. Cumulative leafhopper-days were calculated by averaging 2 successive nymph counts, multiplying by the number of intervening days, and adding these over the 8 count dates.