Wooly Adelgids

 

Tsuga canadensis the year we discovered Adelges tsugae (woolly adelgid)

HWA distribution courtesy NYS DEC

Bad news this year – walking across the creek bridge next to our house I got smacked in the face by a hemlock branch encrusted with Adelges tsugae (wooly adelgids). Currently a serious threat to Tsuga canadensis (hemlock) here in New York, adelgids can kill a tree in as little as four years by tapping directly into the trees food storage cells. One insect can be responsible for orginating as many as 40,000 descendants in a single season!

Hemlock distribution courtesy NYS Hemlock Initiative

This is a big deal in our neck of the woods. Hemlocks are the third most common tree in our forests, and are what is called a “foundation” species. This means they create the ecosystem where they resides. Also a climax species, they are members of a mature forest, and critical components of a clean water system.

 

We have been keeping an eye on the four mature hemlocks in a row here, and even now see not many more adelgids than these, but it is no more likely there are only the adelgids we see than there is only the one house mouse we caught… still, in a spirit of hopeless optimism inappropriate to our current political climate, my husband cut the branch off and burned it in the wood stove. We then sprayed the ground between the tree and the  house with isopropryl alchohol, ’cause some fell off, okay?

 

Zeb Strickland

We like these trees. They are close to the house but not TOO close (like the Norway spruce), and they hold the creek bank near where it likes to flood the road. Even though we assume the many, more ancient hemlocks in our woods won’t benefit much from stopping adelgids down here, we suddenly feel on the front lines of an invasion. These trees are on a direct path to a work site, and we don’t want to become vectors ourselves, spreading the little bastards to uninfected areas.So we have asked Forest and Water Solutions to come have a look.

I met Zeb back when I was part of the Cornell Botanic Gardens Natural Areas Academy for a few years. A great teacher, we spent some time discussing the pro and cons of pesticides and certification in their application. (I got to “shoot” some Japanese knotweed under his supervision, a highlight of my time there.) So we were already pretty confident when we contacted him, and his easy manner and thorough explanation of the process cinched it. We signed up for a single basal bark application for four trees.

Forest and Water Solutions

I was able to stand nearby and watch. It didn’t take long, or cost much. Zeb used two chemicals, one faster acting and the other good for five years or so. For those of you rightly concerned about the over use of pesticides, I was pleased to see how careful and contained the process was. Yes, we could have left these trees alone. Would their death have been certain, or is it possible experiments in the introduction of natural predators would have progressed enough in time to save them? If not, does it matter that these four trees, out of the hundreds near us,survive? I don’t know. We weighed the options and we made this choice. I wish us all luck.

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6 thoughts on “Wooly Adelgids

  1. A scary prospect, the loss of our hemlocks. . A friend treated some trees and I thought he said one chemical was a neonictinoid, famous for killing bees. Did your applicator discuss this with you?

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    • Exactly the kind of concerns we were wrestling with.Hemlock’s are not a big bee pollen source, but he still took pollinators into account, using a basal bark application and applying it later in the year. Here’s a quote from Michigan State: Because hemlock pollen is not usually col­lected by bees, it is unlikely that standard insecticide treatments of hemlock trees to protect against hem­lock woolly adelgids will impact pollinators. However, because abundant amounts of pollen may be pro­duced, contamination of other types of pollen can be minimized by treating hemlock trees with systemic neonicotinoid insecticides in late spring after trees have finished flowering.

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    • You’re right,usually they are quite a bit higher up. HWA have been on our radar for some time, and we even went to a training session at Cornell Botanic Gardens some time ago.

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