Response of swamp bay, Persea palustris , and redbay, P. borbonia , to Raffaelea spp. isolated from Xyleborus glabratus

Summary Laurel wilt is a devastating invasive disease of members of the Lauraceae plant family. It is caused by the fungus Raffaelea lauricola, which is a nutritional symbiont of its ambrosia beetle vector, Xyleborus glabratus. In the United States, six Raffaelea spp., in addition to R. lauricola, have been recovered from mycangia of X. glabratus. We compared the response of two laurel wilt suspects, swamp bay (Persea palustris) and redbay (Persea borbonia), to five of these species, another undescribed Raffaelea sp., and R. lauricola. Six weeks after inoculation, only R. lauricola caused significantly greater symptoms than water inoculations. The fungi varied in their ability to move systemically and be recovered from the host at the end of the experiment. Stem hydraulic conductivity was decreased by R. lauricola, but none of the other taxa. Although the roles these fungi play in the life cycle of X. glabratus are not known, they do not appear to be pathogens on these host tree species.