Abstract An experimental acaricide in various concentrations was applied at various times in the season to single 0.15 acre plots in a randomized block design consisting of 4 replicates of York Imperial and Golden Delicious trees (6 yr old). All treatments except the last were applied on alternate sides with a Myers Mity Mist sprayer calibrated at 50 gpa, 2 mph, 320 psi. Sprays for the last treatment were applied to both sides of trees with a dilute handgun. Dates of application were as follows: 26 Apr (Sunspray 6E oil only) 2 May (all treatments except Oil both sides), 30 Jul (all treatments except Oil, 1 side). The combination of NC-21314 and Carzol was applied on 30 Jul to 1 side of trees. During the season, general maintenance sprays of fungicides (Bravo, Bayleton, Benlate, Captan, and Zineb), insecticides (Lorsban, Dipel, Guthion, Penncap M) as well as calcium chloride were applied with a Friend Airmaster calibrated at 50 gpa and driven 2.3 mph. Average temperatures were: May 58.5° F, Jun 70.3° F, Jul 71.3° F, and Aug 72.6° F. Rainfall in inches totaled: May 4.51, Jun 4.42, Jul 5.86, and Aug 7.33. Effect of treatments on ERM was evaluated by counting mites several times during the season on samples of 25 leaves/tree, 100 leaves/treatment (York Imperial only). S. punctum was observed by 3-min counts of adults and larvae around the periphery of test trees (York Imperial only). Pest pressure was moderate throughout the season.