EFFECT OF CROP HABITAT AND POTATO MANAGEMENT-PRACTICES ON THE POPULATION ABUNDANCE OF ADULT HARPALUS RUFIPES (COLEOPTERA, CARABIDAE) IN MAINE

The effects of crop habitat and potato management practices on adult H arpalus rufipes (Coleoptera: Carabidae) were studied in Presque Isle a nd Stillwater, Maine, during 1990-1992. A relative index of population abundance was estimated using pitfall traps. Rotation crops may harbo r a higher abundance of H. rufipes than potato fields. A higher beetle abundance late in the season was observed in barley rotation crops co mpared with potato. The type of the current year's rotation crop (oats vs. clover) significantly affected H. rufipes abundance; more beetles were found in the small grain than in clover. Factors such as crop pl anting density, weed biomass, or weed seed (barnyard grass) densities did not affect H. rufipes abundance in a wheat rotation crop. Within t he potato crop, these was no significant effect of a previous year's r otation crop (oats vs. clover) on H. rufipes abundance. Organic soil a mendments and insect pest management strategies in potato fields had n o significant effect on adult abundance. The effects of two pesticides used in Maine potato production (a herbicide and a mycoinsecticide) o n H. rufipes mortality were studied in the laboratory. No direct adult H. rufipes mortality resulted from the application of the herbicide m etribuzin or the insect fungal pathogen Beauveria bassiana. (Balsamo) Vuillemin. However, in the field, the combination of an application of metribuzin with chisel plowing significantly reduced H. rufipes abund ance late in the season.