Apple, Airblast Evaluation of Insecticides, 1993

Abstract

Abstract Experimental sprays were applied to 3 tree plots in a randomized block design consisting of 2 replicates of ‘Yorking’ and 2 replicates of ‘Golden Delicious’ with a buffer tree between plots and a buffer row between blocks. These trees were spaced 20 × 30 ft apart and were 19 years old. Experimental sprays were applied with a Friend Airmaster ‘309’ calibrated to deliver 100 gpa at 2.0 mph. Application dates and materials varied between treatments and are listed in the table for WALH. All applications were complete sprays. A routine schedule of fungicides (Dithane 75DF, Nova 40WP, captan 50WP and Benlate 50DF) was maintained throughout the experiment. Effectiveness on SA was evaluated by counting aphid-infested leaves/10 top terminals, and aphids/most infested leaf. The effect of the sprays on WALH was evaluated by counting nymphs/25 injured leaves/tree. Effectiveness of test chemicals on ERM and ZM was evaluated by counting these mites several times during the season on samples of 25 random leaves/tree, 100 leaves/treatment. The effect of sprays on S. punctum was evaluated by 3-min counts of adults and larvae around the periphery of the test trees. STLM were evaluated by a 5-min count of mines around the periphery of the trees at the end of each of the first two generations before peak emergence of adults. OFM shoot injury was assessed by making a 3 min observation around the periphery of each tree and counting injured shoots. Internal feeding lepidoptera were evaluated with a 5-min count of apples exuding frass and the total number of apples evaluated to give percent injured apples. Effectiveness of chemicals on fruit feeders was assessed for injury by scoring drop apples on 6 and 21 Jul and 3 and 16 Aug and picked samples of 50, 100 and 100 fruit per replication on 16 Aug, 3 and 20 Sep, respectively. Pest pressure was extremely high throughout the season. Fruits were rated as 0 (no russet), 1 (raised lenticels), 2 (1-10% russeted surface), 3 (11-25% russeted surface), 4 (26-50% russeted surface), or 5 (>51% russeted surface). Possible ranges are 0-30 (none to raised lenticels) 31-60 (raised lenticels to 1- 10% russeted surface), 61-90 (1-10% to 11-25% russeted surface, 91-120 (11-25% to 26-50% russeted surface), and 121-150 (26-50% to >51% russeted surface). Effects on parasitoids attacking CM and OFM were evaluated several times during the season on a single tree within each plot by picking up to 20 apples exuding frass in a 10-min count and rearing the larvae in the laboratory on a semi-synthetic lima bean diet at 20 °C, 16:8 D:L. Injured apples were collected on 7 and 22 Jun, 7 and 19 Jul, 4 and 18 Aug, and 2 Sept. Larvae of CM and OFM were transferred singly to diet cups on each collection date and monitored several times a week for adult moth and parasitoid emergence for 5 weeks. Two species of braconid parasitoids were found during these evaluations, Macrocentrus delicatus which was by far the most common and Charmon extensor. Rates of parasitism for each treatment were calculated by dividing the total number of parasitoids by the total number of parasitoids plus total number of CM and OFM adults.