Apple, Dilute Test of Insecticides, 1987

Abstract

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 × 10.7 m. Sprays were applied with a John Bean sprayer, 35 gal/min pump, equipped with a spray mast carrying 7 spray guns arranged to wet the uniformly trimmed trees. Approximately 6.3 gal of spray was applied to each replicate tree. Dates of application were 21 May; 3 and 18 Jun; 1, 15, and 29 Jul; and 12 and 26 Aug. For the DPX-42372 treatments, Guthion 50WP was substituted on 3 Jun (high rate only), 1 and 15 Jul, and 12 and 26 Aug. For the RH-7988 treatment, Guthion 50WP was substituted on 21 May, 1 and 15 Jul, and 12 and 16 Aug. General sprays ol fungicides (Benlate, Manzate, Bayleton, Dithane M-45) were made at 1-2-wk intervals throughout the experiment with a Friend Airmaster sprayer at 50 gal/acre. Effectiveness of treatments on AA was evaluated by counting aphid-infested leaves/10 top terminals, and aphids/most infested leaf. Effect of treatments on WALH was evaluated by counting nymphs/25 leaves/tree. Effectiveness of treatments on ERM, twospotted spider mite, and predatory mites was evaluated by counting the mites several times during the season on samples of 25 leaves/tree, 100 leaves/treatment. Effect of treatments on the predator S. punctum was evaluated by 3-min counts of adults and larvae around the periphery of the test trees. STLM was evaluated by a 5-min count of mines around the periphery of the test trees. Effectiveness of treatments on fruit feeders was assessed by scoring for injury all drops after 1 Jul and two picked samples on 19 Aug and 15 Sep. Apple samples averaged 187 fruit/replicate and 748/treatment. Pest pressure was heavy throughout the season. Russet ratings were based i on 30 'Golden Delicious' apples/replicate, 60/treatment. Fruit 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).