THE POTENTIAL OF ENTOMOPATHOGENIC FUNGI AND NEMATODES AGAINST OTIORHYNCHUS-OVATUS L AND O-DUBIUS STROM (COL, CURCULIONIDAE) IN THE FIELD

Laboratory and field assessments were made to determine the root weevi l species composition in some Finnish strawberry fields, to test their susceptibility to common entomopathogenic nematodes and fungi, and to follow the persistence and effects of augmented entomopathogen popula tions under field conditions. The two most common Otiorhynchus species were O. dubius and O. ovatus. In general both species occurred in one field, but the proportions varied greatly with time and site. O. ovat us was active primarily in spring, while O. dubius could be collected later. Most damages occurred in areas with sandy soils. Otiorhynchus l arvae were in the laboratory highly susceptible to entomopathogenic St einernema isolates. Steinernema occurred also naturally in some strawb erry fields. Beauveria bassiana was less effective against root weevil s than the other tested pathogens. Some strains of Metarhizium anisopl iae killed-the pest larvae nearly as well as the nematodes. All tested M. anisopliae strains were also able to persist in soil over several growing seasons. On the contrary, B. bassiana persisted poorly in the soil. Augmented nematode populations were able to persist at least for two years in the strawberry fields. At the area with no weevil infect ion, the persistence of nematode populations was not as good as in the areas with a heavy pest population. Introducing M. anisopliae spores and/or entomopathogenic nematodes to the soil appears reasonable if th ere is a danger of pest infestation. Spores might be better as a preve ntive means, while nematodes can be effective even if the pests alread y exist in the plantation.