OVERWINTERING SURVIVAL AND SPRING EMERGENCE IN MELIGETHES-AENEUS - EFFECTS OF BODY-WEIGHT, CROWDING, AND SOIL TREATMENT WITH BEAUVERIA-BASSIANA

High overwintering mortality was recorded for Meligethes aeneus in the field in Finland, ranging from 85 to 98% depending on the source of t he overwintering population. The main factor explaining variation in s urvival was the body weight of the beetles in the autumn: only the hea viest beetles survived. Body weight, on the other hand, was influenced by treatment of the rape field soil with Beauveria bassiana, resultin g in a 50% decrease in winter survival compared with the reference. Th e soil treatment did not appear to have direct mortality effects (path ogenesis) on the beetle neither in the summer nor in the winter, and t here was no apparent effect on survival of crowding of the insects at the overwintering site. Density dependence in overwintering survival o f M. aeneus may function through the availability of pollen food in th e autumn, and intraspecific competition for it. Treatment of the rape field soil with B. bassiana may be a feasible way to increase the wint er mortality and to lower the pollen beetle populations, but requires further research.