Apple, Evaluation of Foliar-Applied Insect Growth Regulators for Leafroller Control, 1990

Abstract

Abstract Experimental sprays were applied to 4-tree plots arranged in a randomized complete block design. Each plot contained the following cultivars: Delicious, Golden Delicious, Stayman, and Rome Beauty. Each treatment was replicated 4 times. Each plot was surrounded by an adjacent 4-tree plot that was treated twice during each brood with a combination of Lannate 1.8 L plus Asana XL to prevent TABM larvae from dispersing onto treated trees. The trees were planted to a spacing of 12 × 35 ft. Treatments were applied with a truck-mounted John Bean sprayer, 35 gpm pump, equipped with a handgun to thoroughly wet the trees. Approximately 4.6 gal of spray was applied per replicate tree (ca. 475 GPA). Dates of application were Insegar treatment (1 Jun, 9 and 23 Jul); RH-5992 and Penncap M plus Lannate treatments (12 and 25 Jun, and 8 and 24 Aug). During the experiment, general maintenance sprays of Rubigan, captan, and Thiram and calcium chloride, as well as one alternate-row application (18 Jun) and one complete application (29 Jun) of Swat 8 E (0.375 and 0.56 lb (AI)/acre, respectively for aphid control) were applied to all plots. One complete application of Kelthane 35 WP (2.1 lbs (AI)/acre) was made on 21 May to 3 replicates of the Insegar treatment, 4 replicates of the RH-5992 treatment and one replicate of the Penncap M plus Lannate treatment to balance the mite populations across plots. The effect of treatments on mites was evaluated by counts taken several times during the season on samples of 25 leaves/tree (cv Delicious only), 100 leaves/treatment. The effect of treatments on the mite predator S. punctum was evaluated by 3-min counts of adults, larvae, and pupae around the periphery of test trees (cv Delicious and Stayman). TABM leaf shelters and STLM mines were counted by making a 5-min examination of the cvs Golden Delicious and Stayman. Effectiveness of treatments on leafrollers was assessed by scoring for injury all drops after 1 Jul and 1 picked sample of approximately 200 apples/tree on the cvs Rome Beauty, Stayman, and Golden Delicious in late Sep and early Oct. Pest pressure was heavy.