Laurel wilt, caused by Raffaelea lauricola, was discovered in the southeastern USA in 2004,
and has been responsible for the death of many indigenous North American tree and shrub species
in the family Lauraceae. Symptoms of the disease are typical of vascular wilts, in which woody
xylem becomes discolored and nonfunctional due to infection by the fungus, and foliage subsequently
dies due to a lack of water. The vector of R. lauricola is an ambrosia beetle, Xyleborus
glabratus, and trees become infected when beetles bore into tree stems and branches and release
fungal spores from their oral mycangia. The ambrosia beetles produce brood in the trees after wilting.
Although the fungus and beetle are native to Asia, laurel wilt has not been reported on plant
species native to Asia. The purpose of this study was to assess the susceptibility of Asian species
in the Lauraceae to laurel wilt. Most Asian species (Cinnamomum camphora, C. osmophloeum,
Machilus zuihoensis, M. thunbergii, C. jensenianum) developed only a light pale-gray discoloration
in the sapwood following inoculation, but no other symptoms were observed. However,
partial wilt of branches was observed in some inoculated plants of 2 Asian shrub species (Lindera
strychnifolia and a Phoebe sp.). Raffaelea lauricola was isolated from discolored xylem of many
of the inoculated species. Compared to North American lauraceous species such as redbay (Persea
borbonia), the Asian species are more resistant to laurel wilt, but all inoculated host plants showed
some level of susceptibility.