Apple, Leafhopper Test, 1993

Abstract

Abstract A 10 year-old apple orchard, variety ‘Red Delicious’ was used in this test. Single tree plots, replicated 4 times/variety in a randomized complete block design, were sprayed to runoff (ca 3 gal/tree) with a hydraulic sprayer equipped with a handgun operated at 200 psi. Treatments were applied at petal fall (PF—11 May), 5th cover (5th—12 Jun) and 6th cover (6th—3 Aug). The orchard was treated with Captan for disease control as needed. Weekly ERM counts were made by randomly selecting 20 leaves/tree, brushing mites onto glass plates coated with Triton B-1956, and counting motile ERM and AF. Mite-days (MD) were calculated as: MD = MD1 + [(Ml + M2)/2 × 7], where MD1 = mitedays already accumulated, Ml = avg ERM/leaf on a given sample date and M2 = avg ERM/leaf on the next sample date. Leafhoppers (White apple and/or Rose) were evaluated at 1,3, 7, 14, and 21 days post treatment using a 20 leaves/tree (PF) or 50 leaves/tree (5th and 6th) sample. Predatory coccinellids were sampled by 3 minute counts of larvae and adults. At harvest, 100 fruit/tree were collected and weighed, evaluated for spray injury, and rated (0%-100%) for russeting. Data were transformed to sqrt(x + 1) or arcsine(x) before ANOVA and comparison of means.