Selection, application, and pathogenicity of naturally occurring Beauveria bassiana strains against Ips duplicatus (Coleoptera: Curculionidae, Scolytinae)

Norway spruce (Picea abies) stands in Central Europe are increasingly threatened by the northern bark beetle, Ips duplicatus, which is a pest whose distribution and impact have expanded significantly in recent decades. The reduced efficacy of traditional pest control methods against this species underscores the need for innovation management strategies. This study investigates a novel approach that combines modified pheromone traps with the biological control agent Beauveria bassiana, an entomopathogenic fungus. A total of 48 B. bassiana strains were obtained from natural populations of I. duplicatus. Following laboratory testing, two strains (NRID11 and NRID43) were selected for field trials. Carriers of the living organism were inoculated with these strains and then placed in applicators as part of the pheromone traps. The study evaluated the effects of selected strains and different carrier exposure periods on beetle mortality rates. The NRID11 strain showed some percentages exceeding 90 % after 21 days of exposure. However, efficacy decreased to less than 60 % when the carriers remained in the traps for more than 30 days. These findings emphasize the importance of optimizing exposure duration and confirm the potential of carriers inoculated with B. bassiana in modified pheromone traps as a promising biological control strategy against I. duplicatus.