Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Is the wireworm problem a fungus problem?

Wireworms, the larvae of elaterid beetles, cause increasing problems in arable crops, especially in potatos. A possible cause for this situation is an insufficient natural control. To check this hypothesis and in regard of a possible biological control with entomopathogenic soil fungi, we sampled and tested soils from arable land and adjacent meadows at eight locations in the canton Berne. To demonstrate the presence of these fungi we used selective media and the Galleria bait method. We found Metarhizium anisopliae in all soil samples. This fungus causes the green muscardine disease and attacks several species of insects including wireworms. In all cases soils from arable land had less M. anisopliae than soils from meadows. The differences were significant for the density (colony forming units/g soil) as well as for the frequence (percent positive soil samples). This differences may be the result of the use of insecticides as well as of fungicides. The low densities of M. anisopliae may partly explain the problems with wireworms. Beauveria bassiana was found at low densities as further entomopathogenic fungus.

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