Virulence of Different Entomopathogenic Fungi Species and Strains against the Hazel Longhorn Beetle Oberea linearis (Coleoptera: Cerambycidae)

Abstract

The aim of this study was to investigate alternative methods to control longhorn beetle (Oberea linearis) infestations in walnut orchards. Wild isolates of entomopathogenic fungi obtained from soil samples from Greece and Cyprus were tested for their efficacy against adults and larvae of O. linearis. Insect populations were acquired from a heavily infested walnut orchard and individuals were placed in Petri dishes provided with ground walnut wood for larvae and fresh leaves for adults. The tested insects were subjected to 16 different wild isolates from the genera Beauveria, Cordyceps, Metarhizium, and Purpureocillium, where 108 conidia/mL were applied by spraying, and insects were monitored daily for 16 days. The results showed that all the tested fungi resulted in a mortality rate of 66–100%, with Cordyceps fumosorosea exhibiting the highest virulence, causing complete mortality to both larvae and adults. These findings suggest that the management of O. linearis, which has traditionally relied on chemical applications, could transition to an organic approach by utilizing entomopathogenic fungi.