Apple, Dilute Test of Insecticides, 1986

Abstract Experimental sprays were applied to run-off to single-tree plots in a randomized block design consisting of 2 replicates of Golden Delicious and 2 replicates of York Imperial. Treated single trees were separated by others not sprayed with insecticides. The trees were planted to a spacing of 6.1 x 10.7 m. Sprays were applied with a John Bean sprayer, 35 gpm pump, equipped with a spray mast carrying 7 spray guns arranged to wet the uniformly trimmed trees. Approximately 6.5 gallons of spray were applied per replicate. Dates of applications were: 13 and 28 May, 12 and 26 Jun, 15 and 29 Jul, 12 and 27 Aug. For the RH-7988 treatments Guthion 50WP (114 g/100 gals) was substituted on 13 and 28 May, 15 Jul, 12 and 27 Aug. Swat was applied only on 13 May, 12 and 26 Jun, and 29 Jul. On the UC-84572 plus Triton Ag-98 treatment, PA-10 was dropped after 13 May due to excess foaming, Triton AG-98 was substituted in remaining sprays. Effectiveness on the apple aphid was evaluated by counting aphid-infested leaves/10 top termianls, and aphids/most infested leaf. The effect of sprays on white apple leafhopper was evaluated by counting nymphs/25 leaves/tree. Effectiveness of test chemicals on European red mite, twospotted spider mite and predator mites was evaluated by counting mites several times during the season on samples of 25 leaves/tree, 100 leaves/treatment. The effect of sprays on the predator S. punctum was evaluated by 3-minute counts of adults and larvae around the periphery of test trees. Spotted tentiform leafminer was evaluated by a 5-minute count of mines around the periphery of test trees. Effectiveness of chemicals on fruit feeders was assessed by scoring for injury all drops after 1 Jul and two picked samples on 25 Aug and 16 Sep. Apple samples averaged 181 fruits/replicate and 724/treatment. Pest pressure was heavy throughout the season. Russet ratings are based on 30 Golden Delicious apples/ replicate, 120 treatment. Fruits were rated as 1 (no russeting), 2 (light russeting), 3 (moderate russeting), or 4 (severe russeting). Possible ranges were 30-60 (none to light), 60-90 (light to moderate), 90-120 (moderate to severe).