A survey of microbial antagonists of Agriotes wireworms from Germany and Italy

Wireworms of the genus Agriotes (Coleoptera: Elateridae) are severe and widespread agricultural pests affecting numerous crops throughout the world and causing damage of economic importance. Between 2008 and 2011, a survey of the occurrence of natural microbial antagonists of wireworms was conducted. Altogether, 3,420 wireworms and two dead beetles from agricultural habitats and grassland of various parts of Germany and 700 lab-reared wireworms from Italy were screened for the presence of disease. Of these, 283 selected dead and moribund Agriotes specimens were diagnosed by light and electron microscopy for insect pathogens; 66 wireworms contained unspecified bacterial infections; and 86 specimens displayed fungal growth with 25 infected by the entomopathogenic taxa Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea, Isaria spp. and Lecanicillium sp. Nematodes were observed in 29 dead individuals, and 141 individuals showed no distinguishable pathogens. In one dead Agriotes larva, an intracellular bacterium was identified as a new Rickettsiella pathotype named 'Rickettsiella agriotidis'. The survey resulted in a natural infection rate of 0.66 %. The possible use of these pathogens as biocontrol agents is discussed.