Laurel Wilt Update

Ken Rudisill
Horticulture Faculty
Bay
krru@ufl.edu

In a recent issue I wrote about Laurel Wilt, and in that article I mentioned it had not been found in the Panhandle. Laurel Wilt has now been confirmed in Bay County. It has been located in several areas in Panama City. Because of this discovery I am reprinting the article.

The ambrosia beetle is small yet makes a big impact. Photo Credits: Dr. Jason Smith, UF IFAS Extension Forest Pathologist

Laurel wilt is a disease that affects not only the redbay but other trees in the laurel family. Water flow is blocked by a fungus that causes the tree to wilt. The fungus is introduced into the tree by the non-native redbay ambrosia beetle. The disease is spreading rapidly in Florida but has not been reported in the Northwest District.

A red bay tree affected by Laurel Wilt. Photo Credits: Dr. Jason Smith, UF IFAS Extension Forest Pathologist

The ambrosia beetle attacks trees that are usually stressed, dying, or dead. The redbay ambrosia beetle attacks healthy trees of certain species in the laurel family, notably the redbay.  The beetle carries spores of fungi into the tree as it bores into the tree. The fungus grows inside the tree and serves as a food source for the beetles and their larva. When the beetles leave the tree and move to new trees they carry the fungus with them. The beetle will not kill trees unless the fungus is on the beetle.

The leaves of affected trees droop and have a reddish or purplish color.  Wilted foliage can be seen in only part of the crown at first, but usually the entire crown eventually wilts and turns red. In redbay, the leaves eventually turn brown and remain on the tree for up to a year or more.

To reduce the spread of laurel wilt:

  • Don’t use firewood or mulch from redbays (and other laurel family host species) from counties where laurel wilt has been confirmed.

  • Do not transport dead and dying redbay wood (and wood from other laurel family hosts), leave it on site instead.

  • Burn or chip infested host tree material.

  • Sterilize saws and pruning blades after cutting an infected tree and before using them on uninfected host tree species.

  • Report new finds to the Florida Division of Plant Industry (http://www.doacs.state.fl.us/pi/) or Division of Forestry (http://www.fl-dof.com/).

Source: Laurel Wilt: A Threat to Redbay, Avocado and Related Trees in Urban and Rural Landscapes, March, 2008,Albert E. Mayfield III, Jonathan H. Crane and Jason A. Smith, A. E. Mayfield III, Forest Entomologist, FDACS, Florida Division of Forestry, Gainesville, FL; J. H.Crane, Professor and Tropical Fruit Crops Extension Specialist, Tropical Research and Education Center, Homestead, FL; Cooperative Extension Service, IFAS, University of Florida, Gainesville; J.A. Smith, Assistant Professor of Forest Pathology and State Forest Health Extension Specialist, School of Forest Resources and Conservation,IFAS, University of Florida, Gainesville.