Effects of four monoterpenes on the growth in vitro of some Heterobasidion spp. and two Leptographium species

The inhibitory effects of the monoterpenes (-)-α-pinene, (-)-β-pinene, δ-3-carene and myrcene, in both the contact and the volatile phase, on Heterobasidion spp., Leptographium wingfieldii and Leptographium serpens were studied in vitro. Inhibition was usually greater when the monoterpenes were in contact with the fungi than when the fungi were exposed to the monoterpene vapours. Myrcene was the most strongly inhibiting compound for H. annosum s.l., followed by δ-3-carene; the Leptographium spp. were inhibited most strongly by δ-3-carene. Exposure to the monoterpenes reduced conidiogenesis in H. abietinum. After exposure of the fungi to the monoterpenes was discontinued, there were in general no residual effects on fungal growth, apart from Leptographium spp. that had been exposed to δ-3-carene.