Note: An update has been added to this post, and is found below the first set of pictures.

I live in Central Massachusetts, in the town of Holden. We're on the border of the large city of Worcester.

In a previous question, one of my photographs caught the eye of a user here in Massachusetts who is monitoring the Hemlock Woolly Adelgid, an aphid-like tree killer.

This insect is decimating forests and home landscapes all over the country. The New England Area is so badly infested that hemlocks are under quarantine in both Maine and New Hampshire.

It seems the most significant research in New England has been taking place at Harvard Forest, the 3500 acre forest owned by Harvard University. It's located in Petersham, a town about 70 miles west of Boston. Senior Ecologist David Orwig has spent decades studying and educating about what has been called the "woolly bully" at the forest and other regions. His research is getting widespread attention. In April of 2015, The National Geographic published an article entitled Are Harvard's Dying Hemlocks a Warning for Trees Everywhere?

The hemlocks here teem with a pest that’s slowly killing them; their demise is all but inevitable. “I’m hoping some will survive,” said Orwig, the forest’s senior ecologist, “but we’re on borrowed time.”

Because this is such an important issue, I'm concerned not only about my own tree, but also about how to identify the Hemlock Woolly Adelgid while out walking, in order to report it to the proper authorities. I'm hoping other people here can be encouraged to do the same.

First, Is my tree infected?
An excellent publication detailing the life-stages, with pictures, can be found here. My tree doesn't seem to have the large growths that are the hallmark of the mature adelgid, but I do have a lot of leaves with a white dusty coloring, which can be a sign of a young infestation. I did find a woolly-looking thing with pinchers attached to a twig, and a few areas of white netting. There are a few round solid lumps, which I thought might be bird droppings, but the experts would know better about that.

All the pictures below were taken in the first week of March, 2017, except the one with the doves, which is from July of 2016. To save space, I've made all of them smaller. Please click on them to see larger, more close-up versions. Some are blurry, but I have others I'd be glad to post instead if need be. Don't hesitate to ask.

The pictures are as follows:
First row left: The woolly thing, which dried up after I removed it. First row right: The same thing attached to the branch. Second row left: View of a branch with leaves with white dusty covering; an area of white netting joining some leaves; and a small round mass at the bottom. Second row right: Another look at discolored leaves. Third row left: A view of a branch from behind to show the twigs. Third row right: The picture of a branch taken in July of 2016. Fourth row left: A view of the same branch taken on March 2, 2017. Fourth row right: The base of the trunk, which I didn't realize was damaged until last week, when I went out to take these pictures!

Woolly-looking thing Woolly thing on leaves

Thing with white netting and blob Lots of dusty leaves Back view of twigs Doves on branch Last year July 2016 Same branch March 2017 Bare trunk at base with a few dead branches

Update: Shortly after posting this I had the tree examined by a naturalist/ecological arborist who's been studying the adelgid for years and treating trees all over Massachusetts. He said it was very healthy, with good new growth and no evidence of adelgid. He was intrigued by the picture I had posted of the suspected infestation. As part of his research, he's been finding that something had happened, most likely a weather pattern, to cause the adelgids to die off without human intervention. Many previously-infested trees have made remarkable recoveries, most likely including mine. This correlates with information provided by Olin Lathrop's answer below.

He examined all of my trees and plants, and did find some Wooly Adelgid on a hemlock in a completely different area of my yard.

He explained that Wooly Adelgid is identified by the appearance of white, cotton-like masses at the junctions of the twigs and the needles. The wooly substance is a coating covering an adelgid with eggs.

He said my infestation was in a young stage, and didn't cover a large enough section of my tree to be doing major damage. He recommended removing the affected branches, which we did, and keeping an eye on the rest of the tree as we come into the spring and summer. If we see a lot more, and want to treat them, his approach to control begins with spraying the affected area with horticultural oils. The spray coats the adelgids and suffocates them, while not harming the rest of the tree or other plant or animal life. This is the least invasive treatment, and should always be the first choice when possible, especially for a homeowner with only a few trees. If the infestation gets out of control, the next step is to treat the entire tree with an insecticide. Imidacloprid has been used successfully for years, but permethrin seems to have some better qualities, and is becoming more popular. All trees are part of the delicate balance of the outdoor eco-system, and removing them shouldn't be the first course of action.

He agreed that the vicious adelgid is doing tremendous harm wherever it's found. The number of infested trees makes control very difficult, and sadly, especially in forest areas, the adelgids are still winning the war.

I appreciate and give full credit to Olin Lathrop for spotting the problem on the original tree, which precipitated this question. Without his keen eye, and generous help, I would never have had it examined. Then I wouldn't have known I had trouble lurking in a different tree, and probably would have lost it.

Below are pictures of our actual adelgids, taken in March of 2017. They're similar to Olin's, further confirming the correctness of his answer.

small branch large blobs small branch in front of chair enter image description here under side of branch tree above the sick branches

  • 1
    I'm not sure if your pictures show wooly adelgid. It has been years since we saw wooly adelgid on our hemlocks, because we have been successfully treating them with Bayer Advanced Tree and Shrub Protect and Feed. (Long name, but that's what the label says.) Spread the product on the ground under the hemlock once a year in the spring. This is too labor intensive to treat acres of hemlock forest, but we have only about 10 hemlocks. We nearly cut down one hemlock because it was so pathetic, but after 4 years of treatment and some pruning it is once again a handsome tree.
    – ab2
    Mar 12, 2017 at 1:57

1 Answer 1


As far as I can see, only your original picture from 2016 shows sign of woolly adelgid. The tree is not in focus since the point of the picture was the doves, but here are some clues:

The white dots look characteristic of a woolly adelgid infestation, and a rather severe one if the dots can be seen from the top of the branches. Another clue is the defoliation:

Notice how needles are clearly missing in several places, particularly on the branch at lower middle of this snippet.

Here is a typical look of a mature woolly adelgid infestation. It is most obvious on the underside of branches. Often you will find pieces of branches on the ground, such as this one. This picture was taken in Groton MA on 30 Apr 2016:

Often this can only be seen when looking at the undersides of branches. Severe infestations can be seen from the tops of the branches, as this one in Beverley MA on 7 Jul 2016:

What made me originally ask about the time and location of your picture (you've told us time, but I'd still like to know location) was that I observed something unexpected happen during the summer of 2016.

There were several infestations in Groton that were quite evident in the fall of 2014. That winter, one night got down to about -15°F, which seems to have killed off most woolly adelgid in the area. There was very little to be found in the spring of 2015, and thru most of that year. The next winter only got to -5°F, which is apparently not low enough to kill off the pest. Things started off in the spring of 2016 about where they left off in the fall of 2015, with some severe infestations by July 2016.

I didn't monitor the woolly adelgid again until fall, when I tried to find a good candidate location for testing a bio-control. To my suprise, most of the places I checked showed no current signs of adelgid, and even some recovery of the trees. Most trees seemed to have healthy needles at branch tips, even though further back the needles were still lacking that had dropped previously. Here is a good example of the foliage pattern:

enter image description here

This was in Groton on 6 Nov 2016, and characteristic of many hemlocks in the area. Note the unusual pattern of needles at the tips of branches, with no needles further back towards the trunk. There was no adelgid directly visible in this tree and most others, although it could still be found here and there in this stand.

Something interesting happened in the summer of 2016, which I'd like to understand. We had a unusually dry summer, with drought conditions in much of Massachusetts. Most of the hemlocks grow in wet areas, that at least stayed damp. I don't think the drought affected the hemlocks directly, but may have contributed to the adelgid decline.

It seems this should be studied. It would be useful to understand what did in the adelgid during the summer of of 2016. Perhaps this could give a clue towards a new control technique.

I've been trying to connect up with people doing research in this area, with only limited success. If anyone out there is researching this pest, I'm happy to help and be eyes on the ground in the Groton MA area.

  • The picture doesn't show anything obviously wrong with the bark. Woolly adelgid doesn't care about bark anyway. They suck the juice from the stems of the needles. I have been in touch with the central west regional Audubon director. Audubon cares about the problem, but they don't seem to be doing any original research. I think those people are either at UMass or at Fish and Wildlife. Mar 12, 2017 at 22:44
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    @Sue: I'm very suspicious of this "bio-control spray that kills only adelgids". There has been rather limited success with bio-controls. As far as I know, these have only been research tests, mostly down south in Virginia and the like. This research is still ongoing. I am highly skeptical that a commercial bio-control spray for woolly adelgid exists. Find out what specifically he plans to spray, and ask for a copy of the specimen label. I really would like to see that. Anyone applying pesticides on your property must (by law) supply a specimen label to you if asked. Mar 18, 2017 at 12:54
  • @Sue: Who is "the expert" you referred to? If this person is doing active research, I'd like to get in touch with him. Mar 18, 2017 at 12:56
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    The arborist is Jeffrey Hehman. He's been here for a number of different things, and he never seems to charge us any money! That page has his credentials and contact information, so I hope he can be helpful to you. I appreciate the work you people are doing. I'm so tired of the way people mistreat trees, animals, and all living things which are inter-dependent. Some is from a lack of educating people, so researchers and experts like you and he are very important. Mar 19, 2018 at 21:24
  • By the way, other than breaking off a very few small parts of the affected areas of the second tree above we didn't do anything to this or any of our trees, and now, a year later, everything's fine. Those bare branches are happily feeding and protecting small birds. Mar 19, 2018 at 21:31

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