Apple, Dilute Test of Insecticides, 1983

Abstract

Abstract Experimental sprays were applied to run-off to single-tree plots in a randomized block design consisting of two replications of ‘Golden Delicious’ and two replicates of ‘York Imperial’. Treated trees were separated by others not sprayed with insecticides. Experimental sprays were applied with a John Bean sprayer, 35 gal/min pump, equipped with a spray mast carrying seven spray guns arranged to wet the uniformly trimmed trees. Approximately 8 gal of spray were applied per replicate tree. Dates of application were 2 and 18 May (Orthene, Ambush, and Guthion treatments only), 3 and 17 June, 1 and 18 July, 1, 16, and 31 Aug. Orthene and Ambush treatments were only applied on 2 and 18 May and 3 June, and 2 and 18 May, respectively. Guthion was applied to these treatments thereafter. XE-905 was not applied on the last two spray dates. During the season, sprays of Cyprex, Topsin M, Polyram, captan, Rubigan, zineb, and calcium chloride were applied with an airblast sprayer at 50 GPA to the whole experimental block. Average temperatures were: May 57°F, June 68°F, July 74°F, Aug. 72°F, and Sept. 65°F. Rainfall in inches totaled: May 4.98, June 4.42, July 0.83, Aug. 2.01, and Sept. 2.05. Effectiveness on apple aphid was evaluated by counting aphid infested leaves/10 top terminals, and aphids/most infested leaf/infested terminal. The effect of sprays on WAHL was evaluated by counting nymphs per 25 leaves per tree. Effectiveness of test chemicals on ERM and TSSM was evaluated by counting mites several times during the season on samples of 20 leaves per tree, 80 leaves per treatment. The effect of sprays on S.punctum was evaluated by 3-min counts of adults and larvae around the periphery of test trees. Effectiveness of chemicals on fruit feeders was assessed by scoring for injury all drops after 1 July and two fruit samples on 22 Aug. and 19 Sept. Apple samples averaged 217 fruits per replicate and 868 per treatment. Pest pressure was moderate throughout the season. Russet ratings are based on 30 ‘Golden Delicious’ apples per replicate, 60 per treatment. No russet (1), light russet (2), moderate russet (3), and severe russet (4). Possible means are: no russet to light russet 30-60, light to moderate russet 60-90, and moderate to severe russet 90-120.