Laurel Wilt Update

Most of us in the fruit tree clubs have heard about laurel wilt, the deadly fungal disease that affects trees in the Laurel family, including our beloved avocado. It's spread by the red bay ambrosia beetle, which bores into the trunk, inoculating the tree with fungal spores that attack its vascular system. The beetle's advance through Florida has been especially difficult to halt since it can attack native trees including red bay, swamp bay, and sassafras.

Symptoms of laurel wilt include rapid leaf wilt, dieback, and death, but the disease may not be easy to distinguish from dieback caused by root rot or lightning strike. A telltale sign, not always present, is strings of compacted sawdust protruding from the trunk.

A recent article in Growing Produce magazine reports that in Florida, laurel wilt has now been found in 61 of 67 counties. On the relatively positive side, it's classified as “high incidence” only in Miami-Dade County. The beetle seems to prefer bay trees to avocados, and so far there are few known cases of the disease in dooryard groves.

What can you do? Here are several recommendations:

–-Educate yourself about laurel wilt disease. Considerable information including a 10-minute video is available at the Florida Department of Agriculture and Consumer Services. Many other websites have articles and photos.

---Keep your avocado trees healthy with proper irrigation and fertilization. Healthy trees are less attractive to the beetle.

---Buy only local firewood. The beetle can travel long distances in unprocessed wood.

---Do not leave pruned wood from your avocado trees lying around, as this can attract the beetle. My area has weekly collection of "yard waste", the county's term for composting material (joking aside, they do grind it all up, compost it, and make it available to county residents), and I prune avocado trees the evening before pickup so that fresh-cut wood can be removed the next day.

---Report any host trees that appear infected to your local Extension Office or to the Florida Division of Plant Pathology. Do not remove wood from such trees from your property.