Trees In Crisis

Invasive Hemlock Woolly Adelgid (HWA) is decimating America’s Eastern Hemlock Forests.

Trees In Crisis


Hemlock Forests are in trouble.

Eastern Hemlocks are under attack by a tiny invasive pest that destroys a tree in as little as 3-5 years, an entire forest in as little as 6-10. The Hemlock Woolly Adelgid (HWA) is the culprit.

US Forest Service Photo

Native to Japan, HWA was first discovered in Richmond VA in 1951 but is now established in Minnesota, Wisconsin, Michigan and every state along the upper eastern seaboard and the entire Appalachian range. Fully infested forests extend from Maine to Georgia.

Once infested, a tree can die in 3-5 years; an entire forest in 6-10 years…

Why has this Happened?

First, the eastern Hemlock and Carolina Hemlock have no natural defense against HWA. Second, HWA only attacks Hemlocks. Third, HWA has had no natural enemy to control it in N. America. Fourth, it reproduces quickly, often and explosively. Fifth, nothing was done for 50 years. There’s been nothing in its way and only entire Hemlock forests to feed on.

The Bigger Picture: Environmental Decline

HWA kills more than just a tree – it sets in motion a spiral of environmental decline. 

All living organisms that depend upon a Hemlock forest are adversely impacted- including people.

FACT #1: With the death of a Hemlock comes the loss of critical habitat for birds, mammals, and other insects both species depend on. Hemlock forests are utilized by over 96 bird and 47 mammal species. Streams with Hemlock forests contain a higher richness and diversity of aquatic invertebrates and significantly greater trout populations. As Hemlocks die, stream-side shading disappears, water temperatures rise, and trout die.

FACT #2: The Hemlock has a fibrous, water-loving root system that aids in control of erosion and local flooding. The canopy traps and retains moisture, increases humidity, and reduces evaporation. As trees die, the natural ability of the soil to retain moisture diminishes (hydrological failure). Erosion happens and streams and waterways become clogged with sediment.

FACT #3: As HWA weakens a tree’s immune system, the Hemlock becomes vulnerable to other arboreal diseases and harmful insects such as scales and mites that gain advantage over the tree’s natural defense system. HWA makes the Hemlock defenseless.

FACT #4: As trees die, fire hazard rises. Dead trees and underbrush become fuel for forest fires.

FACT #5: The economy that depends on a lush Hemlock forest declines. Hemlock forests provide aesthetic beauty, tourism, and increased property value.

FACT #6: The death of a virgin Hemlock forest removes a valuable resource for wood products. Virgin Hemlock stands represent a large percentage of un-harvested forest in the eastern United States.

FACT #7: Removing dead trees is exorbitantly expensive and hasn’t stopped the invasion.

The destructive impact of HWA goes far beyond the death of a single tree. 

Are your trees infested?

We have the answer.

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