Reproductive Diapause and Host Plants Affect Insecticide Tolerance of Adult Pear Psylla (Homoptera: Psyllidae)

Winterform pear psylla, Cacopsylla pyticola Foerster, in reproductive diapause and collected in the fall were conditioned in the laboratory to either tenninate (long days) or maintain (short days) diapause; conditioning was further divided into insects fed on dormant budwood or pear foliage. Long days promoted ovarian development; this development was enhanced by feeding on foliage compared with domlant wood. Pesticide tolerance was reduced in long day-conditioned pear psylla after diapause compared with those kept in diapause in five of six experiments. Conditioning of host plants also effected pesticide tolerance in two of five experiments. Our results suggest that the known reduction in pesticide tolerance of winterform pear psylla from fall to spring was related to diapause status and not linear age; diapause status, in tum, was affected by host plants. A general decline in control survivorship was correlated with reduced pesticide tolerance after diapause.