Apple, Summer Acaricide Tests, 1991

Abstract

Abstract Dilute sprays were applied to runoff with a handgun sprayer (32 kg/cm2) to single tree plots of apple trees. Treatments were arranged in a randomized complete block design and replicated four times on 'Delicious' cultivar with MM. 106 rootstock. Treatments were separated by unsprayed buffer trees. These trees were ca 2.3 m tall and planted 4 × 6 m apart. A single spray of AC-801757 was applied at the same rate (142 mis form/100 gal) at either half-inch green (10 Apr), pink (1 May), or petal fall (20 May) to compare residual mite control resulting from different early season scheduling (Test 1). Oil (2%) was applied at tight cluster as a standard prebloom comparison treatment. Test 2 was conducted to compare effectiveness of a single spray of different rates of AC-801757 applied early in the season at pink (1 May). Test '3 compared different rates of AC-801757 applied on 23 Jul. Seasonal programs of different rates of Kelthane 50 WP were also tested. Kelthane treatments were applied at petal fall (20 May) and again on 3 Jun and 23 Jul. ERM and the predaceous mites ZM and TP, were sampled on 25 randomly selected leaves from each plot at weekly intervals from 16 May-21 Aug. Mites and eggs were removed from leaves with a Henderson-McBurnie mite brushing machine. ARM were counted on the sampled leaves under a dissecting microscope on one-half of the lower surface of each leaf.