Asian beetle invasion killing sassafras trees

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During recent weeks several people have asked why some of their sassafras trees have died. In the past, nothing affected sassafras. They grow like weeds in abandoned fields and form a dense thicket.

Settlers often used this aromatic tree to make tea brewed from the bark of its roots. The bark, twigs and leaves are also important foods for wildlife.

Although sassafras is not commonly used in the landscape, it has some good aesthetic qualities. It has a beautiful fall color. A sassafras thicket in November is very striking.

Unfortunately, sassafras, like some other native plants, has started to succumb to a pest from another continent. In this case, it is the Asian ambrosia beetle.

The problem began in 2002, when the destructive beetle was found in traps near Savannah, Ga. This beetle is a native of India, Japan and Taiwan. The beetles spread a fungus, called laurel wilt disease, which causes the trees to die.

Currently, there is no known method to halt the spread. Another native tree it is killing, Red Bay (Persea borbonia), started dying in coastal South Carolina by late 2003. At the time, the beetle was found on those dead and dying trees and was suspected. By 2006, it had spread to five counties in South Carolina and 15 counties in Georgia, all near the coast. The latest map I saw online from the Georgia Forestry Commission, from the fall of 2008, showed the spread as far north as Jenkins and Screven counties in Georgia and Allendale and Bamberg counties in South Carolina. The beetles probably arrived in our area in 2011 or 2012.A North Augusta man who e-mailed me said he has seen some of his sassafras trees dying “the last two years or so.”

The beetle burrows into the cambium layer of the tree and deposits the fungus, which then multiplies. The tree is unable to move water and nutrients. The beetle may leave the tree after the initial visit, but once the tree dies large numbers of beetles return to eat the fungus.

The use of pesticides is not practical because they would affect many other beneficial insects. There are no known biological controls, and even if one could be located it would be years before it would be available for release in an infected area.

People sometimes sneak a plant through Customs when they visit another country because they want to try to grow it in our area. This could introduce a new insect or fungus that is devastating to a native plant. Examples include Dutch elm disease, chestnut blight, the gypsy moth and woolly adelgids that are now killing the hemlock trees in the Appalachian mountains.

Spittlebugs

As the rainy season continues, you may find large numbers of spittlebugs coming from either centipede or St. Augustine lawns. Spittlebugs are black with orange stripes. They fly all over the place while you are mowing the lawn, and you wind up with several dead ones on the mower housing when you are finished.

Adults and nymphs feed on the plants by inserting their needlelike beaks into the stem and sucking out juices. The grass can become bleached or yellow, then eventually wither and die if the problem goes unchecked. In most cases, they do not cause enough damage to warrant treatment, but you still need to monitor your grass to make sure.

The nymphs are easily detected. Just look on the grass stems near the soil surface for their distinctive spittle masses. When they are bad you can actually hear a squishing sound as you walk across the grass. Adults fly readily when disturbed and can be flushed from the grass by walking through the affected areas.

Spittlebug infestations can be controlled with several commonly available turf insecticides that contain pyrethroids, such as bifenthrin (Ortho Max Bug-B-Gon), cyfluthrin (Bayer Advanced Multi-Insect Killer), cyfluthrin + imidacloprid (Bayer Complete Insect Killer) or lamba-cyhalothrin (Spectracide Once and Done Insect Killer). Use plenty of water to apply the insecticides because you need to move it through the thatch. With a liquid insecticide, you can achieve the best volume of water with a hose-end sprayer.


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