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Hemlock Woolly Adelgid

Why we care:  These tiny insects secrete white wax as they feed on sap from hemlock shoots and branches.  Hemlock Woolly Adelgid (HWA) feeding can kill needles, shoots and branches.  Over time, growth slows as trees become less vigorous and trees may take on a grayish-green appearance.  Infested hemlocks, especially large, old trees, are often killed when other stress factors, such as drought, affect trees.

What is at risk?
  More than 100 million mature hemlocks grow in Michigan.  Hemlocks provide important habitat and winter cover for many wildlife species.

The threat:
  HWA populations are common in many eastern states, including Pennsylvania.  Eggs and very young adelgids can be carried by birds and can be moved on hemlock nursery trees, logs or firewood.

What could happen in Michigan?
  Much of the state's hemlock resource is relatively old and very vulnerable to HWA.  If this pest becomes established, most of these trees will be killed.

Michigan Departments of Agriculture & Rural Development and Natural Resouces Hemlock Woolly Adelgid Forest Pest Alert 

Small Format Hemlock Woolly Adelgid Forest Pest Alert  

What does Hemlock Woolly Adelgid Look Like?   

USDA-Forest Service Hemlock Woolly Adelgid Pest Alert

Hemlock Woolly Adelgid Look-Alikes


Hemlock Woolly Adelgid Investation History in Michigan

Quarantine Information

Michigan Hemlock Woolly Adelgid Quarantine

Hemlock Woolly Adelgid Quarantine: List of Regulated Counties

Michigan Plant Pest Quarantines

Michigan Quarantine Summary for Licensees

Links of Interest

USDA-FS-Forest Health Protection - Hemlock Woolly Adelgid: Publications and Other Information

USDA-FS-Forest Health Protection - Hemlock Woolly Adelgid: Distribution Maps - Hemlock Woolly Adelgid Gallery

U.S. Fish & Wildlife Service - Hemlock Woolly Adelgid: Climate Change Invites Invasive Insect North

USDA - National Invasive Species Information Center Hemlock Woolly Adelgid: Species Profile

What Can You Do?


If you notice white, waxy material at the base of the needles on hemlock trees, to prevent spread, do not remove potentially infested material from the site, take photos, note the location of the affected trees and report it.

Phone: MDARD Customer Service Center, (800) 292-3939
Midwest Invasive Species Information Network:

Don't Move Firewood