April 24, 2015
By Stan Rosenthal
Often our columns talk about invasive exotic plants but today I would like to bring your attention to a problem caused by both an exotic insect and fungus.
Often when we look at the world around us, we try to simplify things to make sense out of our very complicated world. In this case, the story starts with two trees common to the southeast that are being affected by a recent introduction of both a beetle and a fungus. They are the red bay and the sassafras. The red bay, it is believed, will be eradicated from the southeast. The sassafras will be affected by the disease, but to a lesser affect. Many people have heard of sassafras as settlers often used this aromatic tree to make tea brewed from the bark of its roots. The bark, twigs, and leaves of sassafras are also important foods for wildlife.
The red bay, also an aromatic plant, is in the laurel (Lauraceae) family and can be used as a substitute for the bay leaves you buy in the grocery store. It is often used in Southern cooking to flavor gumbos. Both trees, although not commonly used in urban landscapes, have good aesthetic qualities. The sassafras often produces good fall color, and the red bay has beautiful lustrous evergreen leaves. Beyond the direct usefulness to us, the red bay is an important host to three butterflies: palamedes, Schaus and spicebush swallowtails. The seeds of red bay are eaten by turkeys, quail, deer, songbirds and bears.
In 2002 the destructive Asian ambrosia beetle was found in insect traps near Savannah, Georgia. The beetle is a native of India, Japan and Taiwan. This Asian ambrosia beetle spreads a fungus which causes the red bay trees to die. The name for the disease is Laurel Wilt. Laurel Wilt is spreading now and has affected other species in the Lauraceae family including avocado and camphor trees. At the present time, there is no known method to halt the spread of this disease.
Historically, our failures to stop an unwanted pest from coming into our country has been very costly. Examples in the tree world of North America include Dutch elm disease and chestnut blight.
This newer predicted sad loss of red bay trees from our landscape brings us to the difficult question of how can we keep this from happening. These tight relationships such as this one between the beetle and fungus are often found in nature. The problem is that these relationships are often connected to many other relationships in their place of origin. This complexity when transferred to another continent in bits and pieces can wreak havoc on plants and/or animals native to the receiving continent. Our world is very interconnected now, and so the great expanses of oceans that used to separate the continents are not as effective at limiting the spread of these pests.
More information can be found on Laurel Wilt disease at the following web page maintained by the Florida Department of Agriculture and Consumer Services.
Stan Rosenthal is an Extension Agent with Leon County/University of Florida IFAS Extension. For gardening questions, email us at Ask-A-Mastergardener@leoncountyfl.gov