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The Hemlock Woolly Adelgid

The Hemlock Woolly Adelgid (HWA) is an invasive species of aphid-like insect that attacks hemlock trees. It originated in Asia but in the 1950’s it made its way along the eastern coast of the United States and since into Ontario.  Don’t we have enough going on without another tree disease? Unfortunately we do have another thing to deal with here in Nova Scotia if we have Hemlock trees. Fires, droughts, the elm borer, and other problems caused by climate change it would seem like we have enough to deal with. But still if we have trees and a yard to worry about we are still probably pretty fortunate. Changes in the northern climate have allowed the woolly adelgid to spread and survive in the central and eastern Canadian provinces, including Nova Scotia.

The pest can cause significant damage to hemlock trees, and it spreads rapidly due to its life cycle and ability to be carried by wind, animals, or humans. Therefore, it is essential to monitor and prevent the spread of this invasive species to protect hemlock populations.

The Hemlock Woolly Adelgid is not a good thing.

Symptoms

HWA has a unique life cycle. It is active during the winter months,  reproduces in the early spring and remains dormant during the summer. The adult feeds on the nutrient and water storage cells at the base of the hemlock needles. The eggs are laid at the base of the needles, on the branches, in a white cottony protective mass, usually starting on the lower limbs of the tree. 

Once established, the Hemlock woolly adelgid will rob the tree from its water and nutrients, causing the needles to fade in color and eventually fall off the limbs. The loss of needles will begin at the base and work its way to the top. Death of the tree will occur if the tree is left untreated.