Are your hemlocks naturally resistant to HWA?

Is this hemlock tree at Victoria Park in Truro naturally resistant to HWA?

 Are your hemlocks naturally resistant to HWA?

Hemlock woolly adelgid (HWA) is brutal on hemlocks.  Once infested, it's a death sentence happening in as quickly as three years.

But some hemlocks appear to be naturally resistant to HWA.  There are cases of healthy, green hemlocks standing in a sea of dead ones.

Have you seen any healthy hemlocks surrounded by dead or dying ones?  They may be HWA resistant and an important part of a post-HWA forest.  Please let us know:

  • get a pic with GPS coordinates and send it to 
  • upload your pic to iNaturalist and in the NOTES make a comment about perhaps being HWA resistant
  • use the App TreeSnap to tag trees you find in your community, on your property, or out in the wild. Scientists will use the data you collect to locate trees for research projects like studying the genetic diversity of tree species and building better tree breeding programs.

If you'd like more information with some links to additional information, check out :

In Defense of Plants PODCAST (April 23, 2023) : A fruitful avenue of research involves understanding the capacity for natural resistance in some hemlock trees. Guest Ecologist Ian Kinahan discusses the ins and outs of woolly adelgid resistance and how it may offer a glimmer of hope for North America's hemlock trees.  Thanks to Lucas Machias for the heads up.  Listen here:

Ian Kinahan is the ecologist interviewed in the above Podcast, some of his research.

iNaturalist site dedicated to HWA resistant trees

The Lingering Hemlock Working Group is in the early stages of developing a system for locating and monitoring HWA resistant hemlock

The United States Department of Agriculture have developed hemlock hybrids that are resistant to HWA suitable for horticulture :