Effect of Carzol on Fruit Set, Leafhopper Nymphs and Mites, 1989

Abstract

Abstract This test was conducted in a 10-yr-old orchard with overtree irrigation. The experimental design was a completely randomized block with subsampling. There were 4 treatments replicated 3 times. Each replicate consisted of plots of 10 adjacent trees. Carzol 92 SP (1.38 lb (AI)/acre), a carbamate insecticide/acaricide, was applied to the point of drip with a handgun sprayer operated at 300 psi. Per-acre rates were based on a dilute application of 400 gal/acre. The spray applications were timed to cover the control window for first generation WALH nymphs. This overlaps with the period for use of carbaryl, a carbamate insecticide frequently used as a fruit thinner. Recommended timing for fruit thinning is when fruits are 8-11 mm in diameter. Dates of applications were as follows: petal fall (6 May); petal fall + 1 wk (12 May); petal fall + 2 weeks (19 May). Mean (n = 20) fruit diameter was 10.6 mm on 12 May, and 15.6 on 19 May. WALH densities were determined by counting nymphs on 20 randomly selected leaves per tree on 5 trees/replicate (300 leaves/treatment). Percent fruit set was determined by counting blossom clusters on 19 Apr on two tagged limb sections/tree, and counting the resulting fruit on 15 Jun. Mite population densities were determined on 23 Jun and 28 Jul by taking a composite sample of 100 leaves (10/tree) for each replicate. Leaves were brushed with a mite brushing machine onto glass plates and counted under a dissecting microscope.