Apple, Airblast Evaluation of Insecticides, 1995

Abstract

Abstract Experimental insecticide sprays were applied to 3-tree plots in a randomized block design consisting of 2 replicates of ‘Golden Delicious’ and 3 replicates of ‘Yorking’ with a buffer row between plots. Trees were planted to a spacing of 20 X 30 ft and were 20 yr old. All samples were taken from the center tree in each plot. Experimental sprays were applied with a Friend Airmaster ‘309’ calibrated to deliver 100 gpa at 2.0 mph. Applications dates for all materials can be found in the first table. The second application of the 2 Comply 40 WP treatments was timed for 250° DD after the first emergence of codling moth adults during the first brood. All applications were complete sprays. A routine schedule of fungicides (Benlate 50DF, Dithane 75DF, Nova 40WP, and Ziram 76WP) was maintained throughout the experiment. The effect of the sprays on WALH was evaluated by counting the number of nymphs/25 injured leaves/tree. Effectiveness of the treatments on SA was evaluated by counting the number of aphid-infested leaves/ten top terminals, and the number of aphids/most infested leaf, except the first count where a rating scale (0-4) was used instead of counting live aphids (see table footnotes for scale). The total number of aphid natural enemies was determined by counting the number observed on 10 terminals per tree. Effectiveness of the test chemicals on the ERM was evaluated by counting the mites several times during the season on samples of 25 random leaves/tree, 125 leaves/treatment. The predator, S. punctum, was observed by making 3 min counts of adults and larvae around the periphery of the trees. STLM was evaluated on 6 Jun by counting the number of tissue-feeding mines present on spur leaves only during a 5 min examination around the periphery of one tree/replicate. On 28 Jul and 18 Aug STLM were counted by observing the number of tissue-feeding mines present on shoot leaves only in a 5 min examination. OFM shoot injury was assessed by determining the number of injured shoots per tree in a 5 min examination. Effectiveness of chemicals on all fruit feeders was assessed by scoring for injury on dropped apples on 27 Jun; 3, 17 and 31 Jul; and 22 Aug and picked samples of 35 and 100 fruit per replication on 14 Aug and 25 Sep, respectively. Larvae found feeding internally on all drop and pick samples were collected and identified by treatment. Russet evaluations were made on Golden Delicious fruits (30 per replicate). Each apple was 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). The individual ratings were added to calculate a russet rating for each replicate. Possible ranges for the replicate russet ratings (and estimate of range of % of surface russeted) 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).