To estimate the susceptibility of three foreign oak species, Quercus palustris, Q. robur and Q. rubra, to Raffaelea quercivora, multiple and single inoculations of the fungus to seedlings of these species and Q. glauca, native to Japan, were conducted. In the multiple inoculation, although no seedlings in both control and non treatments were dead, 42% Q. rubra seedlings were only dead in an inoculation treatment whose mortality rates were significantly different among the four tree species. In the single inoculation, proportions of discoloured sapwood in the transverse sections of Q. rubra were significantly higher than those in Q. glauca. These results indicate that R. quercivora has the pathogenicity against a foreign oak species, Q. rubra.

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