Present Status of Biological Control of the Pear Psylla in Southern Oregon1

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Abstract
Studies were conducted over a 3-year period in southern Oregon pear orchards to evaluate the potential of natural enemies of the pear psylla, Psylla pyricola Foerster, to maintain populations of this pest below the levels where direct damage to the fruit occurs. The predators found associated with high pear psylla densities included 13 species of coccinellids, 3 species of anthocorids, green and brown lacewings, and predaceous mirids. This complex was thought responsible for economic control of the pear psylla in I of the 2 orchards studied. The parasite Trechnites insidiosus (Crawford) was found in large numbers in I orchard during I year but was not able to control the pear psylla, because of either nyperparasitism or the influence of pesticides applied in the fall. Where successful biological control was obtained, pear psylla populations were reduced to relatively low levels by midsummer. Predation on the egg stage accounted for 97% of the psylla mortality during the summer period.

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