Pear, Seasonal Pear Psylla Control Experiment, 1990

Experimental sprays were applied to replicated 9-15 tree plots consisting of the cultivar Bartlett (12-yr-old). Each treatment was replicated 4 times. Trees were planted to a spacing of 7.4 × 7.4 m. All treatments were applied with a handgun from a truck mounted hydraulic sprayer at 400 psi. Dates of application were: 28 Mar (bud burst, all plots); 12 Apr (white bud); 2 May (petal-fall); 23 May; 13 Jun (plots 23-27); 6 Jul; 23 Jul; and 30 Jul. Approximately 2.5 gal of spray were applied per tree (190 gal/acre). Treatments were evaluated for PP control by counts of eggs and nymphs at 1- to 2-wk intervals. Counts were made by sampling 10 spur leaves from the middle tree in each replicate. Beginning on 30 May counts were made by sampling 5 spur and 5 distal leaves (3rd most distal leaf) from each tree. On 13 Jun and thereafter 10 distal leaves (3rd most distal leaf) from each tree were sampled. PP pressure was heavy throughout the experiment. Russet ratings are based on 30 Bartlett pears/replicate, 120/treatment. 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 were 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).