Wednesday, March 28, 2007

Infested Hemlocks

The eastern hemlock is in danger of joining the ranks of the American chestnut and the American elm, which have disappeared from the American landscape, unless a solution to an infestation of tiny insects is found. The culprit is the hemlock woolly adelgid (HWA), which was first discovered in the US in 1954 outside of Richmond, Virginia. Today, stands of hemlock from Georgia to Maine have been attacked and are likely to be lost (see map). Rock Creek Park in Erwin is filled with hemlock, and is very much at risk. However, you don't have to go to the national forest to find evidence of the problem. This picture was taken in my backyard. The tell-tale sign of infestation is the fluffy white secretions which shield the adelgid and its eggs. This cottony shield makes it difficult to control with pesticides. At Rock Creek Park, a study has begun to see if a tiny beetle, which is a predator of the adelgid, can keep the infestation in check (read story here). To date, no permanent solution has been found. While an eastern hemlock in a healthy stand may live 400 years, once infected, it takes the adelgid only three to five years to kill a tree. (Click here to read more from the Forest Service's HWA site).

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