NATURAL ENEMIES OF ALFALFA WEEVIL, HYPERA-POSTICA (COLEOPTERA, CURCULIONIDAE), IN MINNESOTA

Alfalfa weevil, Hypera postica, is present throughout Minnesota. Howev er, economically damaging populations seldom occur, due to a combinati on of natural enemies and adverse climatic conditions. Five natural en emies of alfalfa weevil were found in Minnesota. Microctonus aethiopoi des (Hymenoptera: Braconidae), a parasitoid of adults, was recovered f rom 43 of 65 counties surveyed during 1984 and 1985. Tetrastichus ince rtus (Hymenoptera: Eulophidae) and Bathyplectes curculionis (Hymenopte ra: Ichneumonidae), parasitoids of larvae, were each recovered from 13 of 1 5 counties surveyed during 1991-1993. Bathyplectes anurus, anoth er parasitoid of larvae, was recovered from one county in 1991, four c ounties in 1992, and six counties in 1993. Zoophthora phytonomi (Entom ophthora: Entomophthoraceae), a pathogen of larvae, was recovered from 14 of 15 counties surveyed in 1991-1993. Winters with low minimum tem peratures and little snow cover were detrimental to the weevil. Usuall y, southeastern Minnesota has milder winters and higher alfalfa weevil populations than other areas of the State. However, even here, becaus e of natural enemies, weevil populations seldom reach economically dam aging levels.