National Invasive Species Awareness Week – Hemlock Woolly Adelgid

Posted on: February 27th, 2018 by Samantha Kahl

National Invasive Species Awareness Wood, Day 2! 

Today we are looking at the Invasive Hemlock Woolly Adelgid (HWA), and small aphid-like insect that attacks North American Hemlock Trees. Often, the HWA look like white woolly masses (or, ovisacs) found on the underside of branches at the base of Hemlock needles. Ovisacs contain up to 200 eggs and will remain on the tree throughout the year. Native to Asia, the HWA was first found in the U.S. in 1951 and has spread north ever since. These invasive insects currently infect 43 counties within New York State.

White Woolly egg ovisacs.

White Woolly egg ovisacs.

So what do Hemlock Woolly Adelgids do to Hemlock trees that make them so invasive?

HWA’s hatch from the ovisacs and insert very long mouth parts into the tree, at the base of the needles. The insects will remain in the same spot for the rest of their lives, continually feeding on the starches stored within the tree. This process negatively affects the trees by taking in the nutrients meant for the tree limbs and needles. With this process affecting the tree, mortality of the tree occurs within 4 to 10 years of a HWA infestation.

Hemlock Woolly Adelgid attached to the base of a needle on a Hemlock tree.

Hemlock Woolly Adelgid attached to the base of a needle on a Hemlock tree.

How do we control these pests?

There are a variety of methods the State and other organizations have collaborated together to do in order to save our native Hemlock trees. Through the successful introduction of non-native, but non-invasive species for predation, the HWA has been controlled. Insecticides have also been used to treat a tree that has already been infested or as a preventative method in a high-risk area. Though insecticides have been useful in treating individual trees, large forested areas are not ideal.

What happens if you think you’ve found Hemlock Woolly Adelgids ?

The New York State Department of Environmental Conservation (NYS DEC), suggests taking picture of the infestation including a coin or ruler for scale, make a note of the location, fill out the HWA survey form, and send over the report, plus the pictures you take, to DEC Forest Health You can also report the infestation you find on the iMapInvasives map and contact the New York Invasive Species Information (NYIS).

Decrease the spread of HWA and other invasives by cleaning any gear or equipment that has been in or near an infested area!

For more information regarding HWA, check out this neat video by Cornell University!

Check back tomorrow for another interesting Invasive Species in honor of National Invasive Species Awareness Week 2/26-3/2 2018! AWSMP Publications & ResourcesFacebookTwitterInstagram