The redbay ambrosia beetle (RAB) attacks healthy trees of certain species in the laurel family, including avocado trees. What makes this insect so dangerous is the disease-causing fungus it carries. The fungus, commonly called laurel wilt, is carried in sacs located in the beetle’s mouth. Once the beetle carries the fungus into the wood of a tree, the fungus moves through the water and nutrient transport system of the tree, plugging the flow of water and causing the tree to wilt. Leaves typically turn a reddish or purplish color. Most trees infected with the fungus die quickly.
RAB is about 2 mm long, and is dark brown to black in color. Female beetles fly and greatly outnumber the smaller, flightless males. Unfortunately there is not much to detect before the tree becomes infected. After infection RAB tends to attack the tree in large numbers and can leave sawdust tubes protruding from their bore holes.
RAB is native to India, Japan, Myanmar, and Taiwan. The origin of laurel wilt fungus is uncertain, but it is presumed to have been introduced with the beetle. Neither the beetle nor the fungus is known to be a pest in its native range.
This pest-disease complex is a big problem in the southeastern U.S. It likely arrived on infested wood packing material such as a crate or pallet used to ship commercial goods. It has spread quickly through Georgia, South Carolina and Florida. It has not yet arrived in California, but is expected.
What can you do to help? Don’t purchase firewood, tree trimmings or mulch from areas infected with RAB. Purchase only insect- and disease-free containerized avocado trees from reputable nurseries. Stay informed. If your tree shows signs of laurel with disease, please contact our office or the County of Ventura Agricultural Commissioner.
Photos of this pest can be found at this University of Florida website.