Hemlock Woolly Adelgid

The Hemlock Woolly Adelgid (HWA) is one of few insects active during the winter months, and so now is the perfect time to be on the lookout for this tiny invader. Hemlock Woolly Adelgid (HWA) is an invasive insect native to Japan. We think it was introduced in the mid-1900s when Japanese ornamental plants became very popular in American gardens. This tiny insect is specific to evergreen hemlock trees (Tsuga spp.), attaching to new branchlets and feeding on the hemlocks starchy liquids. This continuous feeding weakens the trees and can kill it over the course of about six years. HWA has caused the death of millions of hemlocks along the Appalachians, and gray, ghostly forests are moving ever northward into New York.

HWA egg sacs are the most visible form of the insect, seen from October-May, a time when most insect predators are not active. Egg sacs are found on the underside of hemlock branches and look like small, white, fuzzy blobs, like the tip of a cotton swab.

HWA reproduces twice a year, allowing for exponential population growth in a short period of time. NYS Parks is taking an active role in managing new infestations of HWA. Chemical insecticides, applied very specifically to individual hemlocks, are the best method of control. In addition, NYS Parks has released predatory insects as biological controls in several state parks, with the hope they will one day keep HWA populations in check. Parks just hosted two HWA volunteer training events in Western NY to help us determine presence/absence areas.

Now is the perfect time to be on the lookout for HWA. For more information, or to report sightings in NYS Parks, contact  invasives@parks.ny.gov

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