STATEWIDE DISTRIBUTION OF PARASITOIDS OF THE ALFALFA WEEVIL IN TENNESSEE

The alfalfa weevil, Hypera postica (Gyllenhal), is the most important insect pest of alfalfa, Medicago sativa L., in Tennessee. In 1994, a 2 -yr statewide research project was initiated to monitor alfalfa weevil and its biological control agents in 21 alfalfa fields in nine counti es. Alfalfa weevils overwintered both as eggs and as adults. Parasitis m of all field-collected larvae (n = 6,215) was 11.39%, whereas parasi tism of all field-collected adults (n = 460) was 0.43%. Bathyplectes a nurus (Thomson) and Bathyplectes curculionis (Thomson), parasitoids of alfalfa weevil larvae, were recovered in all counties sampled. In eas tern and middle Tennessee, B. anurus was the predominant larval parasi toid, suggesting B. anurus has displaced the previously predominant B. curculionis in these areas of Tennessee. Percent parasitism of alfalf a weevil larvae by B. anurus and B. curculionis was 7.12% (n = 6,215) and 4.12% (n = 6,215), respectively. Statewide, Microctonus aethiopoid es (Loan) was recovered in low numbers, suggesting poor establishment of this parasitoid of adult alfalfa weevils in Tennessee. Zoophthoora phytonomi (Arthur) Batko, a fungal pathogen of alfalfa weevil larvae, was detected from early March to late April. Because few follow-up stu dies have been undertaken to determine the establishment and distribut ion of these introduced parasitoids in Tennessee, this research should provide baseline information to improve biological control of the alf alfa weevil in Tennessee.