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The Hemlock Woolly Adelgid
Information Regarding This Invasive Pest


The small white cotton ball looking puffs on this hemlock's branches are the pests. The Hemlock Wooly Adelgid is not dangerous to humans and can usually be treated fairly easily.

Native to Eastern Asia, the hemlock woolly adelgid (HWA) was first discovered in America around 1951, in Richmond, Virginia. It is a very small pest that can have dire consequences on the eastern hemlock, Tsuga canadensis, and the Carolina hemlock, Tsuga caroliniana, two tree species that are found throughout the eastern United States.

It is estimated that 90% of the total geographic range of hemlocks in North America has been affected by HWA. This insect will feed on the sap of hemlock trees by inserting its long stylet into the trunk of a tree, very similar to the spotted lanternfly's feeding habit. (Click HERE to be directed to an article on the Spotted Lanternfly.)

While a single insect itself is only about 0.8 millimeters in length, groups of them are easily visible and look like small cotton balls clustered together on the branches of hemlock trees.

If a tree is infested, the HWA can take approximately 4 to 10 years to completely kill the tree. The HWA will cause the tree to loose its needles and prohibit any new growth. Furthermore, if the tree naturally withstands the infestation, it will be more likely to succumb to other secondary diseases.

The North Carolina Cooperative Extension Service from the campus of North Carolina State University suggests, "the safest insecticides for controlling HWA are foliar sprays with either horticultural oil or insecticidal soap." To read more about this pest, click HERE.

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August 18, 2019, 12:57 am PDT

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