Laurel wilt is a deadly disease of redbay and other native plants in the laurel family. The disease is caused by the fungus, Raffaelea lauricola, which is introduced into host trees by a non-native insect, the redbay ambrosia beetle, Xyleborus glabratus. The fungus quickly plugs the water-conducting cells of an affected tree and causes it to wilt.
This insect vector attacks healthy trees. These beetles can be difficult to identify so a specialist should be consulted for positive identification.
Laurel wilt is a deadly disease of redbay and other native plants in the laurel family including sassafrass, pondberry and avocado. The disease is caused by a fungus which is introduced into host trees by a non-native insect, the redbay ambrosia beetle. The fungus quickly plugs the water-conducting cells of an affected tree and causes it to wilt. Laurel wilt is rapidly spreading through the southeastern coastal plain and threatening plants in the laurel family elsewhere in the U.S., as well as, the global avocado industry. Redbay ambrosia beetle and the laurel wilt fungus pose a severe threat to cultivated and wild avocados in California, Mexico, and Central and South America.
The fungus spreads naturally when it is carried to a new plant by a redbay ambrosia beetle (Xyleborus glabratus). This beetle is a member of a group of insects, known as ambrosia beetles, which carry fungi (“ambrosia”) necessary for their young to develop. The fungus is carried inside pouches of the mouth on adult ambrosia beetles. When these beetles bore into wood to lay their eggs, they infect their tunnels or galleries with this fungus. Ambrosia beetle larvae feed on this fungus. Artificial spread of the beetle and fungus can occur when an infested plant, log or piece of firewood is moved from one place to another. Laurel wilt is just one of many significant “pests” that can spread to new areas by people. Unwanted pests and plant diseases can move into new areas unknowingly on firewood or live plant material. One way to help limit human assisted spread of these plant pests and pathogens is by burning firewood where you cut it. Learn more about human assisted spread of plant pests and pathogens at http://www.dontmovefirewood.org/
Trees and shrubs in the laurel family are known to be affected by laurel wilt. Redbay, Persea borbonia appears to be the most widely affected species. Other species that have developed the disease in the field include sassafras (Sassafras albidum), pondberry (Lindera melissifolia), pondspice (Litsea aestivalis), and avocado (Persea americana). Visit our image gallery for photos of these common laurel wilt hosts.
Symptoms vary depending on host species. Plants with laurel wilt have leaves that droop. Leaves turn reddish or purplish, eventually turn brown and die. Redbay leaves change color and remain attached for a year or more. At first you may only see symptoms in only a portion of the crown, but gradually the entire crown becomes discolored and wilts. Remove the bark on a laurel wilt infected plant to find dark streaked discoloration on the surface of the sapwood. This discoloration can also be seen in cross section. In advanced stages of the laurel wilt disease, signs of the redbay ambrosia beetle may be evident. Look for tiny exit holes, sawdust or sawdust tubes that remain intact on the bark of trees.