Seasonal Insecticide Evaluation for Pear Psylla, 1997

Abstract

Abstract Experimental sprays were applied to single-tree replicated plots in a block of ‘Bartlett’ (84%), ‘Bosc’ (9%), and ‘D’Anjou’ (7%) pears. Trees were planted to a spacing of 24 X 24 ft and were 18 years old. Each treatment was replicated 4 times in a randomized block design. All plots except the dilute treatment of M-96-018 were applied with an Friend Airblast ‘393’ sprayer calibrated to deliver 100 gpa at 2.1 mph. The dilute treatment of M-96-018 was treated with a handgun at 400 psi from a truck-mounted sprayer equipped with a Kohler 23-gpm pump. All plots received a regular fungicide maintenance schedule of Benlate 50 DF, Agrimycin, and Ziram 76 WP. All treatments were evaluated by counting eggs and/or nymphs from leaf samples using a binocular microscope under 10X magnification at 4-17 day intervals. Counts were made on 15 spur leaf samples from 5 May to 27 May, on 8 spur and 7 third most distal leaf samples on 2 Jun, and on 15 third most distal leaf samples from 9 Jun until 10 Jul. The cumulative number of PP nymph days per leaf was determined for each treatment from 5 May to 10 Jul. Adult PP were sampled by making a 2-min observation around the periphery of each tree. Russet evaluations were done on pear fruits (30 per replicate). Each replicate 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% rus-seted surface). The individual ratings were added to calculate a russet rating for each replicate. Possible ranges for the replicate russet ratings (and esti-mate 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 moderate throughout the season.