Using Bursaphelenchus mucronatus to demonstrate the potential nematicidal effect of Beauveria bassiana on pine wood nematode (Bursaphelenchus xylophilus) under in vivo conditions

Abstract Key message This study demonstrates the potential of Beauveria bassiana (Bals.—Criv.) Vuill. to control Bursaphelenchus mucronatus (Mamiya and Enda), which is close to Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle but is a non-quarantine pathogen and, therefore, may be used as an alternative organism on which to perform in vivo assays without biological risk. Context Pine wilt disease (PWD) is a serious threat for conifer forests worldwide. It is caused by Bursaphelenchus xylophilus, the pine wood nematode (PWN). In affected areas, eradication and subsequent disease containment measures are being implemented. The latter are, to date, based on control strategies for the insect vectors (Monochamus spp.) and on screening for genetic resistance in tree hosts. However, an integrated pest management strategy which also implements nematode control is still not fully developed. Aims This study aimed to use Bursaphelenchus mucronatus, as an organism on which to demonstrate the nematicidal potential of Beauveria bassiana, an entomopathogenic fungus successfully tested on Monochamus spp., on PWN under in vivo conditions. Methods To this end, a pathosystem was built to simulate these conditions and to bring the nematode B. mucronatus, the insect vector, and the fungus into contact. Results The results show (i) very similar responses of the two nematodes confronted to the fungus and its mycotoxin beauvericin under in vitro conditions and (ii) a remarkable antagonistic effect of B. bassiana on B. mucronatus also on the abovementioned pathosystem (in vivo conditions). Conclusion Our findings have significant implications for the pine wilt disease control. In particular, this study demonstrates the potential of B. bassiana as a biological control tool to be implemented in a future integrated disease management strategy.