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Treating hemlocks with insecticide

PMSS Receives Grant for Treatment of Hemlock Trees

Kentucky Department of Fish and Wildlife Resources has provided to the Pine Mountain Settlement School the recommended insecticide to treat all of its hemlock trees against infestation of the hemlock woolly adelgid (HWA.) The HWA threatens to wipe out all eastern hemlocks (tsuga canadensis) in the eastern United States.

In July 2008, Environmental Education staff conducted an extensive survey to identify the number of eastern hemlock on PMSS property, including the 348-acre James E. Bickford State Nature Preserve. More than 4,900 eastern hemlocks were counted during this survey. HWA was not found on every hemlock, but it was present in every survey area.

The HWA is a tiny exotic insect that feeds on the sap of hemlocks. Scientists believe it is spread by birds, deer, and human activities. After millions of the HWA attach themselves to a hemlock, the insects consume the sap, which depletes the tree's starch reserves. This depletion limits the tree's ability to grow and produce new shoots. Tree death is slow, occurring in two to twelve years. During this time, needles drop, branches and tips begin to dieback, and foliage thins. The lower branches die back completely before the tree dies.

The eastern hemlock plays a vital role in the North American mixed mesophytic forest. Loss of the eastern hemlock will cause the following: the amount of light filtering through the forest canopy will increase, water temperatures will increase in riparian zones along streams that were previously shaded by hemlock, soil composition will change, invasive plants may appear in areas no longer occupied by hemlocks, and several species of birds, insects, and animals that depend on the eastern hemlock for food will be affected.

The HWA is found in 18 states and has caused extensive damage to hemlock populations in North Carolina, Tennessee, and South Carolina. The HWA was first identified in the southeast in 1951 in Richmond, Virginia, but was not found in Kentucky until March of 2006, when it was identified by the Kentucky Division of Forestry on the south side of Pine Mountain, near Rebel Rock on Laden Trail. Three months later, the HWA was found on approximately 500 trees on the James E. Bickford State Nature Preserve at PMSS.

This insecticide used to treat against the HWA, Imidacloprid, will be injected into the soil near infected trees, allowing the tree to absorb the chemical through its roots. This is the most cost effective treatment available and it is especiallyeffective in the early stages of infestation. A HWA eradication crew will assist PMSS staff in treating hemlock trees this spring.
We appreciate the support of the Kentucky Department of Fish and Wildlife Resources and Save Kentucky's Hemlocks, a coalition of concerned citizens, non-profits, and governmental agencies working to save eastern hemlocks in Kentucky.

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