Airblast Concentrate Insecticide Evaluation on Apple, 1997

Abstract

Abstract Experimental insecticide sprays were applied to 2-tree plots in a RCB design consisting of 3 replicates of ‘Golden Delicious’ (only 2 replicates for the control plot) and 2 replicates of ‘Yorking’ with a buffer row between plots. Trees were planted to a spacing of 20 X 30 ft and were 22 years old. All samples were taken from one tagged tree in each plot. Experimental sprays were applied with a Friend Airmaster ‘309’ calibrated to deliver 100 gpa at 2.0 mph. Application dates for all materials are given in the table containing data on WALH. The 5 Jun application for all plots corresponded to approximately 250° DD (base 50° F) after the first emergence of coding moth adults during the first brood. All applications were complete sprays. A routine schedule of fungicides (Benlate 50 DF, Dithane 75 DF, Nova 40 WP, and Ziram 76 WP) 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/10 top actively growing shoots, and the number of aphids/most infested leaf, 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 shoots per tree. Effectiveness of the test chemicals on ERM and AF 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 by counting the number of tissue-feeding mines present during a 5 minute examination around the periphery of one tree/replicate. 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 dropped apples for injury on 8 and 21 Jul; 4, 11 and 19 Aug; and 3 Sep, and picked samples of 40 and 100 fruit per replication on 19 Aug and 18 Sep, respectively. Russet evaluations were made on Golden Delicious fruits (30 per replicate). Each replicate (2) 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). Pest pressure was high throughout the season.