PARASITOID COMPLEX OF EUCALLIPTERUS-TILIAE (HOMOPTERA, DREPANOSIPHIDAE) IN NORTHERN CALIFORNIA

Trioxys curvicaudus Mackauer was imported into northern California in 1970 for control of the linden aphid, Eucallipterus tiliae (L.). In 19 91, it was found no farther than 40 km from the release sites, but in this area it is the dominant primary parasitoid attacking the aphid. T his limited distribution is attributed mainly to the scarcity of favor ed hosts; climatic of conditions play a contributory role. In 1992, T. curvicaudus was introduced and established in San Rafael, partially d isplacing the previously dominant T. pallidus (Haliday); however, it d id not provide satisfactory control of the aphid. Five other primary p arasitoids were reared from the linden aphid: T. tenuicaudus Stary, Ap helinus Subflavescens (Westwood ), A. sp. nr. perpallidus Gahan, A. au tomatus Girault, and an undescribed Trioxys species (the lane are new host records). Ten hyperparasitoid species were recovered, with new ho st records for Pachyneuron californicum Girault and Coruna clavata Wal ker on Trioxys, Alloxysta xanthopsis (Ashmead) on Aphelinus, and a spe cies from the Alloxysta megourae (Ashmead) complex on Trioxys and the subgenus Aphelinus (Mesidia). Hyperparasitoid species ranged from patc hy to well distributed. Syrphophagus aphidivorus (Mayr) was reared at a significantly higher rate from Aphelinus hosts than Trioxys hosts.