Partly buried stem segments and stumps of thinned trees were treated with basidiospores at varying densities to test the likelihood that spread of Armillaria novae-zelandiae into Pinus radiata plantations in New Zealand is occurring through the colonisation of woody material by airborne spores. Colonisation of stem segments was confirmed at densities ranging between 20 million and 5 spores/cm² of exposed cut surface. Degree of colonisation was not influenced by the presence or absence of a protecting wood disc placed over the surface after treatment. In one study, the incidence of colonisation was significantly greater in segments taken from trees felled 3 weeks rather than 3 months earlier, but colonisation was still effective in the older material. The colonisation of freshly cut pine stumps was also demonstrated at densities exceeding 13 million spores/cm² surface, but stumps may be less receptive to spore colonisation than stem segments. Tiny mycelial ribbons present beneath the bark of stem segments but not stumps in all studies were found to belong to Rosellinia thelena, a species newly recorded in New Zealand.