A. Vainio et Hmt. Hokkanen, THE POTENTIAL OF ENTOMOPATHOGENIC FUNGI AND NEMATODES AGAINST OTIORHYNCHUS-OVATUS L AND O-DUBIUS STROM (COL, CURCULIONIDAE) IN THE FIELD, Journal of applied entomology, 115(4), 1993, pp. 379-387
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.