Esteya vermicola Controls the Pinewood Nematode, Bursaphelenchus xylophilus, in Pine Seedlings

Esteya vermicola (Ophiostomataceae) is an endoparasitic fungus that has great potential as a biological control agent against the pinewood nematode Bursaphelenchus xylophilus which causes pine wilt disease. We tested E. vermicola for control of pine wilt disease by spraying E. vermicola conidia on artificial wounds on pine seedlings, and the optimum E. vermicola treatment density and application time were also investigated in the greenhouse. The wounds were similar to those made by sawyer beetles (Coleoptera: Cerambycidae). Esteya vermicola treatments significantly increased the survival rate of pine seedlings that were infected by pinewood nematodes. Wounded plants sprayed with 10⁷ CFU/ml E. vermicola had a 73.0% greater survival rate than nonwounded pine seedlings treated similarly. The treatment of pine seedlings with 10⁷ CFU/ml E. vermicola 14 d before nematode infection increased their survival rate by 90.0%. The number of pinewood nematodes isolated from dead pine seedlings sprayed with E. vermicola was 76% less than the number of pinewood nematodes in the controls. Moreover, infected nematodes and the hyphae of E. vermicola were detected in the dead or wilting pine seedlings. Therefore, spraying E. vermicola on the wounds of pine seedlings made by sawyer beetles provides good control of the pine wilt disease that is caused by pinewood nematodes.