Apple, Airblast Evaluation Experiment of Acaricides, 1995

Abstract

Abstract A number of experimental and registered acaricides were evaluated for activity against two phytophagous mites and toxicity to a number of mite natural enemies. The acaricide treatments were applied to single-tree plots in a randomized block design consisting of 1 replicate of ‘Golden Delicious’ and 3 replicates of ‘Yorking’. The trees were planted to a spacing of 20 X 20 ft and were 22 yr old. All treatments were applied with a Myers Mity Mist sprayer calibrated to deliver 100 gpa, driven at 2 mph. Spray dates were 30 Jun all treatments and 13 Jul TD-2365, Agri-Mek and Kelthane treatments. All plots received a regular maintenance schedule of fungicides (Nova 40WP, Penncozeb 80WP, Topsin 85DF and Ziram 76WP) and nutrients (CaCl). Post-bloom insecticides (Guthion 50WP, Swat 8EC) were applied as needed at I - to 2-week intervals beginning at petal-fall in early May. Effect of the treatments on ERM, TSSM and ZM was evaluated by counting the mites at approximately weekly intervals during the season on samples of 25 leaves/tree, 100 leaves/treatment. Stethorus was observed by making 3-min counts of adults and larvae around the periphery of the trees. Russet evaluations were made on Golden Delicious fruits (30 per replicate). The apples 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). The individual ratings were added to calculate a russet rating for each replicate. Possible ranges for the replicate russet ratings (and estimate of range of percentage of surface russeted) 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).