The potential of entomopathogenic fungi and nematodes against Otiorhynchus ovatus L. and O. dubius Stroem (Col., Curculionidae) in the field
1993
Vainio, A. (Helsinki Univ. (Finland). Dept. of Applied Zoology) | Jokkanen, H.M.T.
Laboratory and field assessments were made to determine the root weevil 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 populations under field conditions. The two most common Otiorhynchus species were Otiorhynchus dubius and O. ovatus. In general both species occurred in one field, but the proportions varied greatly with time and site. O. ovatus was active primarily in spring, while O. dubius could be collected later. Most damages occurred in areas with sandy soils. Otiorhynchus larvae were in the laboratory highly susceptible to entomopathogenic Steinernema isolates. Steinernema occurred also naturally in some strawberry fields. Beauveria bassiana was less effective against root weevils than the other tested pathogens. Some strains of Metarhizium anisopliae 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 infection, 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 there is a danger of pest infestation. Spores might be better as a preventive means, while nematodes can be effective even if the pests already exist in the plantation
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