Observations on the Natural Control of the Pear Psylla, Psylla pyricola Förster, in California

Abstract

AbstractStudies in 1961 and 1962 showed that several naturally occurring conditions suppress the pear psylla. Temperatures above 100°F. caused mortality of nymphal stages and reduced adult oviposition. Crystallization of honeydew was a mortality factor in a few instances, and seemed to be associated with high temperature and low humidity. Absence of new growth and poor condition of leaves caused a steady decline in pear psylla numbers in abandoned orchards. Anthocoris antevolens White was an effective predator in unsprayed orchards and significantly reduced pear psylla populations. A parasite, Trechnites insidiosus (Crawford) was encountered, but its significance as a mortality agent was not determined.