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Hemlock Woolly Adelgid

Scientific Name

Adelges tsugae (Annand) (Annand 1928)

Common Name

Hemlock Woolly Adelgid (HWA)

Native To
Date of U.S. Introduction

Discovered on the West Coast in the 1920s, but it is disputed whether this was an introduced or native population; an introduced population was discovered on the East Coast in the 1950s (Havill et al. 2006; Orwig et al. 2003)

Means of Introduction

Accidental (Wallace and Hain 2006)


Destroys Eastern hemlock trees (Tsuga canadensis) (Orwig et al. 2003)

Hemlock Woolly Adelgid

Hemlock Woolly Adelgid, Adult with wax removed


Michael Montgomery USDA, Forest Service

Find more images


  • Hemlock Woolly Adelgids & Their Predator Beetle, Laricobius nigrinus

    • Sep 22, 2020
    • USDA. FS. Southern Research Station. CompassLive.

    • Laricobius nigrinus is a small beetle that eats an even smaller bug – the hemlock woolly adelgid, or HWA. Since 2003, Laricobius has been used to help control HWA. But the beetle, which is native to western North America, is only active during the fall, winter and early spring. Recently, USDA Forest Service research entomologist Bud Mayfield and his colleagues, including students and prominent researchers, published the results of a six-year collaboration on Laricobius as biocontrol.

      Silvicultural recommendations for managing HWA are still in development. But when they are available, Mayfield and his colleagues plan to update their resource manager’s guide. They wrote the guide for managers who want to use an integrated pest management strategy to control hemlock woolly adelgids.

  • New Manager’s Guide for Controlling Hemlock Woolly Adelgids

    • Sep 24, 2020
    • USDA. FS. Southern Research Station. CompassLive.

    • Forest Service scientists have published a guide synthesizing best practices for controlling these tiny bugs. It promotes a strategy of combining insecticide use with adelgid-eating insects.

Distribution / Maps / Survey Status



Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Federal Government
International Government
State and Local Government