Relationship between virulence and adhesion of the entomopathogenic fungus Beauveria amorpha (Strain: HpBa-1) to the yellowish elongate chafer, Heptophylla picea (Motschulsky) (Coleoptera: Scarabaeidae)

Abstract

We isolated an entomopathogenic fungus, Beauveria amorpha (Strain: HpBa-1), from Heptophylla picea larva. When the larvae were inoculated with HpBa-1, 90.0% cumulative mortality was obtained in 30 days. However, the cumulative mortality was low when the larvae were inoculated with Metarhizium anisopliae (Strain: PMA-7) isolated from H. picea larvae. The high virulence of HpBa-1 to H. picea larvae was analyzed by investigating the conidial adhesion and germination of HpBa-1 on larval cuticle. Numerous HpBa-1 conidia adhered to the H. picea cuticle and most conidia on the H. picea cuticle remained over time. HpBa-1 conidia germinated on H. picea cuticle 96 h postinoculation. However, few PMA-7 conidia adhered to the H. picea cuticle as compared to HpBa-1 and did not germinate on the cuticle 96 h postinoculation. From these results, conidial adhesion and germination on the cuticle of H. picea is one factor causing high virulence of HpBa-1 to the larvae.