South Arkansas residents are already familiar with the threat posed by emerald ash borer, but a new threat to trees has emerged in North Louisiana.
Laurel wilt, a devastating disease of a number of Louisiana trees in the Lauraceae family, has recently been confirmed in sassafras trees in Union Parish. Union Parish is located south of Union County.
The disease is caused by a fungus that clogs the water-conducting tissue of the tree. As a result, the affected tree wilts and eventually dies, according to LSU AgCenter “Plant Doctor” Raj Singh.
“Trees currently susceptible to laurel wilt include redbay, sassafras, pondberry, pondspice, swampbay, camphor tree, spicebush, avocado and California laurel,” Singh said. “Initial symptoms of laurel wilt are rapid wilting and drooping of leaves. Later on infected trees exhibit reddish to purplish-brown discoloration of foliage, and the entire crown will turn brown.”
Brown leaves remain attached to the branches for one year or more in the case of redbay, but shed quickly in other host trees. Removing bark from infected trees reveals black discoloration of sapwood, Singh said.
The fungus is carried from infected to healthy trees by the invasive redbay ambrosia beetle. Both beetle and fungus also may spread to new locations indirectly by moving infested firewood from areas where laurel wilt and redbay ambrosia beetle are prevalent.
“The redbay ambrosia beetles are brown to black and very small (2 mm) in size,” Singh said. “Initially, the redbay ambrosia beetles may attack the branches, and the infested trees may not look wilted. Later on, the trees start to wilt and toothpick-like tubes composed of fine sawdust produced by the insect can be seen on the bark.”
Early symptoms of laurel wilt can be easily misdiagnosed with the damage caused the black twig borer, Singh said.
The black twig borer attacks small-diameter branches and kill infested branches.
People who notice symptoms of laurel wilt on susceptible host trees listed above, contact Singh at 225-578-4562.