Abstract
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.
Highlights
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
Survival rate of pine seedlings in 2012: From March 1 to December 26, 2012, the survival rates of wounded and unwounded pine tree seedlings that were sprayed with E. vermicola and infected with pinewood nematode (PWN) were investigated (Table 2)
The survival rates of pine seedlings increased to 73.0% 6 3.3%, 59.0% 6 4.3%, and 50.0% 6 3.2% after 6 mon in response to spraying with 107, 105, and 103 CFU/ml E. vermicola on the wound, respectively
Summary
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. 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. The pinewood nematode (PWN), Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, is the causal agent of pine wilt disease (PWD) (Kiyohara and Tokushige, 1971) The spread of this nematode occurs via pine sawyer beetles (Monochamus spp., Cerambycidae), which are attracted to pine trees for feeding or oviposition (Mamiya and Enda, 1972). We artificially inflicted wounds that were similar to those caused by the sawyer beetle on healthy pine seedlings that were uninfected with PWNs and sprayed E. vermicola on these wounds to control PWD.
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