Does Gnomoniopsis castanea contribute to the natural biological control of chestnut gall wasp?

Gnomoniopsis castanea has been reported as the causal agent of necrosis of chestnut wasp (Dryocosmus kuriphilus) galls. The fungus is frequently observed on galls in chestnut stands infested by the insect in Italy. In the present study the impact of gall necrosis and the dynamic of its development have been studied in mature and young Castanea sativa stands in Central Italy during spring and early summer, before the D. kuriphilus adult flies. Results suggest that gall necrosis develops from resident endophytic inoculum of G. castanea. During the 2 y of monitoring, no differences were found in incidence and severity of the disease. Gall necrosis increased exponentially during the season, reaching 75,4% of galls totally necrotized in the investigated site in mid July. Gall necrosis was shown to have a severe impact on D. kuriphilus vitality, mostly impacting the adults inside the galls. Gall necrosis by G. castanea appears to efficiently control gall wasp in chestnut stands, although the high virulence of the fungus to chestnut fruits precludes its use as biocontrol agent in biological control strategies.