Journeys in ancient and old growth forests

HWA Newsletter

Good news and bad news in 2017

published Oct 31 2017

HWA found in Nova Scotia

very old hemlocks in Kejimkujik National Park (photo credit Matthew Smith)

Hemlock woolly adelgid was confirmed in Nova Scotia this summer. The infestation is widespread in five counties and was likely present for over ten years before detection, according to Matthew Smith, an ecologist at Kejimkujik National Park. There’s significant hemlock mortality at one site near Yarmouth.

Its not clear how HWA arrived in Nova Scotia – possibly hitchhiking on birds or carried in a wind event. Humans are always a potential suspect. But many of Nova Scotia’s old-growth forests have an important hemlock component, and may be threatened by the adelgids.

First detection of HWA in Adirondacks

This summer something happened that many forest ecologists have been awaiting with dread: HWA was confirmed in New York’s Adirondack Mountains. The Adirondacks are known for having abundant (and commonly old-growth) hemlock forest, so detection of adelgids there is obviously of great concern.

In October the infested trees, and a buffer of trees around them, were treated with insecticides – this is the best control measure for HWA (cutting trees is not considered effective) and will hopefully slow the spread of HWA in the Adirondacks. Vigilance by the public can also help control the spread of HWA – the telltale woolly masses on the underside of twigs are visible roughly Nov-July.

The hunt is on for Ontario’s oldest hemlock trees

Ancient Forest Exploration & Research is seeking out the oldest hemlocks in the province, in anticipation of the arrival of HWA. Michael Henry, an ecologist with AFER, says he expects to find trees over 400 years old, and hopefully beat the current Ontario record of 460 years – but the odds of finding old trees are increased by knowing what to look for. “We’re using visual cues that anyone can learn to recognize, to choose the trees that we want to age,” Henry says. These signs of old age include sinuous (curved or snake-like) trunks, large upper branches, and trunks with very little taper. Trees that are believed to be old are aged by extracting a tree core (a pencil-shaped section of wood) so that annual growth rings can be counted. Knowing where old-growth hemlock forests are found can help prioritize areas for conservation once HWA establishes in the province. If you think you know where an old hemlock is located, send an email to

Biocontrol rearing facility established at Cornell

New York State Hemlock Initiative is now the home of a Hemlock Woolly Adelgid (HWA) Biological Control Research lab, the focus of which is to study the rearing, establishment, and spread of HWA predators to provide long-term management of HWA throughout New York. The establishment of the lab is a huge step forward for New York State, and also has implications for Canada.

“Insects we are currently studying are Laricobius nigrinus (Coleoptera: Derodontidae) and the silverflies Leucopis argenticollis and L. piniperda (Diptera: Chamaemyiidae), from the Pacific Northwest,” the websitestates. “It is our hope that they will have a widespread impact on HWA and offer long-term survival for eastern hemlock populations without continued use of chemical controls.” News from the NYS Hemlock Initiative includes:

• Spring 2017: Released nearly 2,000 Leucopis spp. silverflies at 10 sites in New York State, with successful establishment at all sites

• October 2017: Trip to Pacific Northwest to collect Laricobius nigrinus beetles for lab colony, hopefully with some leftover for wild release

• November 2017: Official opening of biocontrol research facility at Cornell University

Biocontrol appears to be working in New Jersey

Laricobius nigrinus beetles were first released in New Jersey in 2005, and more than a decade later they have dispersed to many areas where HWA are found and they appear to be controlling the adelgids. In a article Mark Mayer of the New Jersey Bureau of Biological Pest Control says that “Pretty much every hemlock stand north of Route 80 and west of Route 287, if you’ve got adelgid in there, you’re going to find beetles. I think right now, it’s not getting worse [and] where we first released the beetles … those trees are looking pretty good.”

HWA detection season longer than we thought?

This striking photo above, taken August 10 in Nova Scotia, by Matthew Smith, shows the wool of HWA very clearly despite being very late in the season. Ideal HWA detection season is late winter through spring / early summer, but it’s worth keeping in mind that wool may be present from late October to mid-July or even later – for at least nine months of the year HWA can be spotted by flipping over the branches and checking for wool at the base of the needles. In many places members of the public have been the first to detect HWA – so check for it when you’re walking in hemlock woods from now through July.



Winter HWA update

Published Feb 10, 2017

IMG_8247Winter: HWA detection season is here

HWA is most visible in winter and early spring, so watch for the characteristic white woolly masses on the underside of branches when you’re skiing and hiking.

HWA established in Michigan

From an article by Michigan State University Extension:

“An insect responsible for the loss of much of the eastern United States Appalachian region’s hemlock trees has found its way into Michigan. The hemlock woolly adelgid poses a threat to the state’s valuable hemlock stands. A call to action by citizens may be the most realistic path to further detection and control.”

MSU extension is coordinating the eyes on the forest program.

Eastern hemlock project on inaturalist

Inaturalist is a website and app that can be used to record observations of any species. The eastern hemlock project is now on inaturalist.

We’re especially interested in locating old-growth hemlock forests, which should be a priority for management.

We’re also very interested in hemlock hedges, which are important for rearing biocontrol organisms (more on this below).

And we’d like records of hemlock woolly adelgid, particularly near the front of its range expansion, to help fellow naturalists track its progress (please also report HWA to official agencies!).

Seeking hemlock hedges

“Hedges made of hemlock trees with thriving populations of HWA are prime candidates for biocontrol. Why? Because predators are easier to catch on a hedge, making it easier to monitor predator establishment and to collect them in order to introduce them in other locations.”

The NY State Hemlock initiative is seeking hemlock hedges, infested with HWA or not. Outside NY State? Add your hedge to our inaturalist project!

June HWA update

published June 9 2016

June: HWA is still visible

Although it’s past the optimum detection season, hemlock woolly adelgid (HWA) can still be visible for the next month. Keep an eye out for it when you’re in hemlock stands in southern Ontario

Article in Blazing Star

Here’s an article that provides a good introduction to HWA, with an Ontario focus. PDF can be downloaded here:

HWA map showing Ontario

This is the first map showing HWA detections in and around Ontario. It is up to date for 2015 and we’ll work on a new one incorporating this spring’s data soon. Clearly the Niagara Peninsula is most at threat. However since HWA is carried by birds, Long Point is another area of concern, and the north shore of Lake Ontario may also be at risk. Infestations carried on nursery stock could appear anywhere. CFIA reports that their monitoring didn’t detect HWA in the Niagara Gorge in 2016. Let’s hope for the best, but it could still easily be present in the canopy where it is difficult to detect.

This map of HWA infestation was created using 2012 data from USDA, and 2015 information from PAMINY. Ontario data is from the Canadian Forest Service, and CFIA personal communications.

The map is by county; highlighted counties may be only partially infested. Particularly near the front of HWA expansion this will exaggerate the abundance of HWA – on the other hand, infestations can sometimes go undetected for years which has the opposite result.

HWA winter mortality was high in 2016

Some interesting results from Vermont this spring, where adelgids suffered high mortality despite a relatively warm winter:

“The annual HWA winter mortality study was conducted recently by the Department of Forests, Parks and Recreation (FPR). The results were a bit of a surprise, though they seem to match results from other northeastern states. Many parts of the region seem to be experiencing high winter mortality rates. The four Vermont sites have rates ranging from 93.8 to 99.0 percent…  Theories for why the mortality rate was so high in a mild winter abound. It is always good in these discussions to remember that there is always variability in nature. So, the timing of cold exposure is important. Other important variables seem to include the magnitude and rate of temperature fluctuations. This winter winter certainly had many large temperature swings.”

While the news is encouraging, the article also points out that because of the enormous fecundity of HWA, and two generations per year, even a single adelgid surviving the winter can produce up to 30,000 offspring by the following year.


This newsletter was brought to you by Ancient Forest Exploration & Research. Please forward it to anyone who might be interested.

We’re still looking for high value hemlock forests for our hemlock mapping project, please send us details on mature or old-growth hemlock forests that you know of in southern Ontario.

To learn more about HWA in Ontario go to and to learn more about how and when to monitor for HWA go to

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