The non-native redbay ambrosia beetle, Xyleborus glabratus, vectors a newly described fungus, Raffaellea lauricola. Both are natives of Asia first discovered in the U.S. near Savannah, Georgia in 2002. In 2003, local newspapers reported the mysterious death of redbay trees, Persea borbonia, on Hilton Head Island, South Carolina and surrounding areas. Subsequent surveys showed that thousands of redbay trees were dying in the low country of South Carolina and Georgia. By the end of 2004, officials on Hilton Head estimated they had lost 75-80% of the island's redbays. The decline of redbay trees has been rapid, and in 2013 it was estimated that nearly all redbay trees larger than 1 inch in diameter on the island have been killed. This beetle/fungus combination now ranges from the southern part of North Carolina to the southern tip of Florida, decimating mature redbay trees in its path. In addition to redbay trees, they also threaten other members of the laurel family including sassafras (Sassafras albidum) and avocado (Persea americana).
The beetles can attack trees smaller than 1 inch in diameter but do very poorly in them. The beetles thrive in large trees, which may explain why these are killed first. Recently dead redbay trees attract redbay ambrosia beetles by the thousands. Each female bores a tunnel into the wood, inoculates the tunnel with the fungus, and lays its eggs. The beetle larvae eat the fungus, mature to adults, and leave the tree to attack others. The whole process from attack to emergence of new beetles can happen in 50 days depending on the time of year. Each female produces an average of 23 young but can produce up to 300. The scale of these attacks, with 20-300 beetles produced per attack and thousands of attacks per tree, helps explain why this beetle and its fungus has spread so rapidly and is decimating large redbay trees.
Southern Research Station scientists studying the beetle’s biology and life history have found that the beetle is attracted to chemicals produced by redbay trees. Although these chemicals are not commercially available in pure form, they are found in the essential oil extracts of other plants, such as manuka and cubeb. These oils can be used to attract beetles to traps.
Work by Southern Research Station entomologists continues on many fronts including attractants, host susceptibility, long-term population trends of the beetle, and the potential of biological control. Contact Jim Hanula, Steve Fraedrich or Bud Mayfield for more information on this exotic beetle and its associated fungus.
Find research publications about the redbay ambrosia beetle on Treesearch.