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Posted 4/8/2016

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By Kyle Kraynak
U.S. Army Corps of Engineers Pittsburgh District

Rangers from the U.S. Army Corps of Engineers Shenango River Lake and Tionesta Lake attended a Pennsylvania Department of Conservation and Natural Resources workshop about the Hemlock Woolly Adelgid, March 3.

The Hemlock Woolly Adelgid is an invasive species that lays eggs at the base of the tree’s needles where it meets the branch. The insects feed on hemlock’s sap eventually killing the tree.

Once infestation occurs, if not treated, it takes three to five years for the tree to die. Each female Adelgid can lay between 100 - 300 eggs per year. The insects have impacted the Great Smokey Mountains region, where areas of untreated trees have completely died off.

Unless funding is made available to treat the hemlocks at district facilities, tree populations in this area may completely die out. Although Shenango has small populations of the tree, the problem is more pronounced in the forests around Tionesta and other flood control projects.

Chemical treatments are available and have proven effective for killing the insects. The insects also react negatively to severe winter conditions.  But with this year’s mild winter, there is the possibility of a resurgence of the forest pest.

The hemlock is the state tree of Pennsylvania and its groves are extremely important for cooling streams for trout and other aquatic organisms. Research shows that these trees can have up to a seven degree cooling effect on streams and creeks that they shade. According to Shenango River Lake rangers the loss of hemlock trees in western Pennsylvania alone could mean a loss of millions of dollars in revenue for the state in fishing and recreation spending.


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