Preliminary evaluation of insect-pathogenic Hypocreales against Leptoglossus occidentalis (Heteroptera: Coreidae) in laboratory conditions

Abstract

Leptoglossus occidentalis, a species native to North America, is considered a major pest of conifer seed orchards in its natural area of distribution. Recently, the seed bug was accidentally introduced into southern Europe and its populations have been expanding throughout Europe. In the course of population study of this seed bug in Slovakia, two entomopathogenic fungi were identified from dead individuals, Isaria fumosorosea and Beauveria bassiana. In the present study, we evaluated pathogenicity of six indigenous isolates of three entomopathogenic fungi, B. bassiana, I. fumosorosea and Metarhizium anisopliae, to adults of the exotic coreid bug under laboratory conditions. All the isolates were virulent to the seed bug, but pathogenicity varied significantly among the isolates. Generally, isolates obtained from naturally infected L. occidentalis were more virulent than those isolated from soil samples. The LC50 values, as estimated by probit analysis, ranged from 0.86 to 84.68 × 105 conidia/ml and I. fumosorosea isolates reached the lowest median lethal concentrations. The results of this bioassay showed that I. fumosorosea a has potential as a microbial control agent of L. occidentalis.