Selective Control Program for the Pear Pest Complex in Southern Oregon

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Abstract
Selective chemical control programs were evaluated in four southern Oregon pear orchards with the goal of maximizing effect of biological control agents for suppression of pear pests. The programs used prebloom oil sprays for control of San Jose scale, Quadraspidiotus perniciosus (Comstock), and for ovipositional delay of pear psylla, Psylla pyricola Foerster; diflubenzuron for codling moth, Cydia pomonella (L.), suppression; Bacillus thuringiensis Berliner for leafrollers; and, where needed, half the usual rate of cyhexatin for spider mite control. Organophosphates, carbamates, pyrethroids, and amitraz were deleted from selective programs. Predator density increased in all selective plots and was sufficiently high in two of the four orchards to give commercially acceptable control of pear psylla and to lower acaricide use by 75%. Control costs were ca. $300 per ha and $700 per ha in selective and standard programs, respectively. Density and period of colonization by pests and predators varied from site to site and appeared to depend on previous treatment history within the study area, and on the nature and management of surrounding vegetation.