Control of deep-seated fungal infections in raw logs of radiata pine continues to be a challenge for achieving consistent and satisfactory protection of high value logs destined for export markets. To develop solutions for this problem, a study was undertaken to investigate inhibition of spore germination and growth of sapstaining fungi by volatiles released from a selection of natural products. Both established mycelium and spores of Alternaria alternata, Cladosporium hebarum, Leptographium procerum and Sphaeropsis sapinea were exposed to volatile compounds released from filter paper treated with camphor, citronella, clove oil, eugenol, eucalyptus oil and tea tree oil, respectively. Growth of fungi was assessed at 3, 7 and 14 days of exposure to the volatiles. After 14 days exposure to volatiles, viability of each fungus species was determined, and microscopy was undertaken to assess fungal morphology. Results showed that all candidate natural products arrested mycelial growth of the fungi tested and also, but variably, affected colour intensity of fungal melanisation. All volatiles inhibited spore germination of all test fungi except for camphor, which inhibited C. hebarum and L. procerum spore germination, but not that of A. alternaria or S. sapinea. Of the natural products tested, clove oil and eugenol vapour consistently killed established mycelium during 14 days exposure which was confirmed by microscopical observations. Volatiles released from clove oil and eugenol also prevented colonisation of radiata pine sapwood by S. sapinea. The present research suggests that biofumigation may offer a possible approach to combat deep-seated fungal infections in radiata pine logs. Future research is required for screening of additional natural products and for determining their effect on infections located below the wood surface.

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