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

Abstract

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