Pear, Seasonal Insecticide Evaluation for Pear Psylla, 1996

Abstract

Abstract Ten insecticide treatments, either single compounds or combinations of various insecticides, were evaluated for their ability to control PP on a seasonal basis. The 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 at a spacing of 24 X 24 ft and were 17 years old. Each treatment was replicated 4 times in a randomized block design utilizing the cv. Bartlett. Experimental sprays were applied 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 50DF, Streptomycin and Ziram 76WP. All treatments were evaluated by counting eggs and/or nymphs from leaf samples using a binocular microscope under 10X magnification at 3-12 day intervals. Counts were made on 15 spur leaf samples from 6 May to 20 May, on 8 spur and 7 third most distal shoot leaf samples 28 May, and on 15 third most distal leaf samples from 6 Jun-27 Jun. Adult PP were sampled by making 2-minute observations around the pe-riphery of each tree. Russet evaluations were made on pear fruits (25 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% russeted surface). The individual ratings were added to calcu-late a russet rating for each replicate. Possible ranges for the replicate russet ratings (and estimate of range of % of surface russeted) are 0-25 (none to raised lenticels) 26-50 (raised lenticels to 1-10% russeted surface), 51-75 (1-10% to 11-25% russeted surface, 76-100 (11-25% to 26-50% russeted surface), and 101-125 (26-50% to >51% russeted surface). Pest pressure was moderate throughout the season.