Factors affecting the occurrence of entomopathogenic fungi in soils of Slovakia as revealed using two methods

Abstract

Soil samples from 901 sampling sites in Slovakia were collected during 2008 and the presence of entomopathogenic fungal species from the order Hypocreales was evaluated. Entomopathogenic fungi were detected in 430 samples by the Galleria mellonella bait method (GBM) and in 627 soil samples using selective medium (SM) containing cycloheximide and dodine. There was a significant difference between the ability of these methods to detect the fungi. Four species were detected by the GBM: Beauveria bassiana (31% of samples), Metarhizium anisopliae (8%), Isaria farinosa (6%), and Isaria fumosorosea (6%). Only three species were detected with SM: B. bassiana (36% of samples), M. anisopliae (37%), and I. fumosorosea (9%). In addition, some samples that were positive using SM were negative with the GBM and vice versa, implying that these methods are not equivalent for the determination of the occurrence and distribution of entomopathogenic fungi. Our results indicated that B. bassiana preferred natural habitats, particularly forests, though it was also frequently detected in other habitats. I. farinosa was strictly limited to forest habitats and I. fumosorosea was most frequently detected in soil samples from hedgerows. M anisopliae was observed primarily in field and meadow samples, and its occurrence was not negatively affected by intensive agriculture. It was most frequently found in lowland soils with a neutral or alkaline pH. Detection of B. bassiana and I. farinosa significantly increased with increasing altitude and decreasing soil pH. Both fungi also preferred soils with high organic content.