Ophiostomatoid fungi can emit the bark beetle pheromone verbenone and other semiochemicals in media amended with various pine chemicals and beetle-released compounds

Abstract

Abstract Fungal volatile compounds can mediate fungal-insect interactions. Whether fungi can emit insect pheromones and how volatile chemicals change in response to chemicals the fungi naturally encounter is poorly understood. We analyzed volatiles emitted by Grosmannia clavigera (symbiont of the mountain pine beetle) and Ophiostoma ips (symbiont of the pine engraver beetle) growing in liquid media amended with compounds that the fungi naturally encounter: (−)-α-pinene, (+)-α-pinene, (−)-trans-verbenol, verbenone, or ipsdienol. Nine volatile compounds were identified among the fungal and amendment treatments. Volatiles qualitatively and quantitatively differed between fungal species and among amendment treatments. The bark beetle anti-aggregation pheromone (−)-verbenone was detected from both fungi growing in (−)-trans-verbenol-amended media. G. clavigera and O. ips can emit beetle pheromones and other beetle semiochemicals, suggesting that ophiostomatoid fungi could contribute to the chemical ecology of bark beetles. However, such contributions could be modulated by the presence of other environmental chemicals.