Effects of predators on control of pear psylla

Studies have been conducted for the past two seasons on the action of predators against the pear psylla. Most of the work has been done at the University of California Deciduous Fruit Station, San Jose, on a block of pears that has been left untreated. The trees at this orchard had received all cultural requirements except the application of pesticides. The orchard suffered heavily from pear psylla attack from 1959 through 1961. In 1962 predators (anthocorid bugs and lacewings) brought the pear psylla population to a low level. The trees (Winter Nellis on Old Home-Farmingdale root-stock) responded by growing vigorously, whereas in previous seasons, growth had nearly ceased and the foliage was yellow and sparse. Studies were continued in 196S to determine if the predators would continue to regulate the pear psylla population.