Apple, Concentrate and Dilute Acaricide Evaluation Test, 1992

Abstract

Abstract Treatments were applied to single-tree plots in a randomized block design consisting of 3 replicates of ‘Yorking’ and 2 replicates of ‘Golden Delicious’. Trees were planted to a spacing of 20 x 20 ft and were 19 years old. All treatments were applied with a Myers Mity Mist sprayer calibrated to deliver 100 gal/acre, driven at 2 mph, except for HHE-3736 70 WG and Savey 50 WP which were applied dilute to run-off with a high pressure handgun at approximately 4 gal of spray per tree. Application dates varied between treatments and are as listed in the tables. All plots received a regular maintenance schedule of fungicides (captan 50 WP, Nova 40 WP, Penncozeb 80 WP and Topsin 85 DF) and nutrients (Solubor and CaCl). Post-bloom insecticides (Guthion 35 WP, Lannate 1.8 L) were applied at 1- to 2-wk intervals beginning at petal-fall in early May. Effectiveness of treatments on ERM was evaluated by counting mites at approximately weekly intervals during the season on samples of 25 leaves/tree (125 leaves/treatment). Effects of treatments on SP were measured by 3 minute counts of adults and larvae around the periphery of trees. Russet ratings are based on 30 ‘Golden Delicious’ apples/replicate, 60/treatment. Fruits were rated as 0 (no russet), 1 (raised lenticels), 2 (1-10% russeted surface), 3 (11-25% russeted surface), 4 (26-50% russeted surface), or 5 (>51% russeted surface). Possible ranges are 0-30 (none to raised lenticels), 31-60 (raised lenticels to 1-10% russeted surface), 61-90 (1-10% to 11-25% russeted surface), 91-120 (11-25% to 26-50% russeted surface), and 121-150 (26-50% to >51% russeted surface).