Entomopathogenic fungi of the genus Beauveria and their pathogenicity to Ips typographus (Coleoptera: Curculionidae) in the Vitosha National Park, Bulgaria

Ips typographus is a serious pest for forestry in Eurasia. Effective control is difficult due to its cryptic habits and insect pathogenic microorganisms, including entomopathogenic fungi that are believed to be a promising alternative to the traditional control measures of this pest. In 2018, diversity of entomopathogenic fungi of the genus Beauveria was studied in populations of I. typographus in the Vitosha National Park, Bulgaria. Two species, B. bassiana and B. caledonica, were identified and 33 in vitro strains were obtained. Phylogenetic positions of the strains were evaluated according to phylogenetic inferences based on ITS and TEF-1α. Pathogenicity of the strains against bark beetles was tested in laboratory. All strains were pathogenic, although there was some variability in the efficacy of B. bassiana strains. Virulence of the five most pathogenic strains (four B. bassiana strains and one B. caledonica strain) was compared with the commercial mycoinsecticide Boverol® and highly-virulent B. bassiana strain ARSEF 12957 isolated from I. typographus in Slovakia. The strain from Boverol® was least virulent and the Slovak strain ARSEF 12957 was more efficient than the Bulgarian strains, but the difference was not significant. The laboratory experiments suggest that the Bulgarian strains have a potential for the control of bark beetle adults.