The Dundas Valley's Hemlock Pest Shows Itself in November, Just as Firewood and Wreath Season Begins

Turn over a low hemlock branch along a creek in the Dundas Valley this winter and look at the underside of the twig, where each needle meets the wood. The Canadian Food Inspection Agency describes what you may find there as white woolly sacs that look like small cotton balls or snow clumps. According to the Invasive Species Centre, the sacs can be seen from November to May and get easier to spot late in winter, from March to May.

They belong to the hemlock woolly adelgid, and its visible season is about to start. That timing matters in Pleasant Valley. The trails off Governors Road are where the insect has been confirmed. Hamilton's city limits are where the federal rules on moving wood and greenery apply. Both come into play during the same weeks, when firewood gets packed for cottage weekends and fresh boughs come indoors for the holidays.

The Insect Is Already Spread Across the Valley

Hemlock woolly adelgid is an invasive, aphid-like insect. It feeds on eastern hemlocks by pulling water and nutrients out of the needles. In a February 2026 report to its Conservation Advisory Board, the Hamilton Conservation Authority said an infestation typically kills a tree within 4 to 15 years, no matter how old or healthy the tree is.

Hamilton's first detection was at the Royal Botanical Gardens in 2023. In 2025, an Invasive Species Centre grant let HCA hire two summer field staff. They surveyed trees and built an inventory, starting at Lower Spencer Conservation Area and working west into the Dundas Valley Conservation Area. The HCA report says they found the adelgid throughout that area, in a pattern suggesting the pest is "present in low numbers but widespread."

That matters because hemlocks are a big part of the valley's forest. HCA estimates there are more than 20,000 eastern hemlocks in the conservation area and expects the adelgid to kill many of them. Eastern hemlocks tend to grow on north-facing ravine slopes near water, and some stand close to HCA trails and infrastructure. HCA warns that as these trees decline, erosion, water quality and hazard trees could become problems. HCA also says there is no long-term solution yet. Research is underway to certify a biological control agent for use in Ontario.

Which Hemlocks Get Protected First

HCA can't treat 20,000 trees, so its plan picks a much smaller group. The plan's approach, called Strategy 5, protects hemlocks right beside creeks. In this riparian zone, HCA says, the trees control erosion and keep streams cool enough for fish habitat.

The narrowing from the whole valley to year one looks like this:

The plan works on a four-year cycle, treating a different set of priority trees each year. Each treatment is an injection at the base of the trunk with a product called IMA-jet. HCA's report says plainly that IMA-jet is a neonicotinoid, a class of pesticide that kills any species feeding on the treated tree, not just the adelgid. The report says the management plan weighed cost, impact and the published science before choosing this method. HCA's Board of Directors adopted the plan and Strategy 5 on March 5, 2026. The same motion asked staff to look at other HCA lands and to consider treating more trees if more funding comes in.

HCA's quotes put the cost of having a contractor treat 150 to 300 trees a year at $10,000 to $20,000 per year. That money is in its 2026 invasive species budget. Hazard tree removal and replanting are budgeted separately. At its September 3, 2026 meeting, the board recorded a $10,000 Invasive Species Action Fund grant installment to support the plan.

The City of Hamilton runs its own program next to HCA's. A September 14, 2026 communication update to Council says City forestry staff chose 174 eastern hemlocks on City land beside the newly detected infestation. They are at Highland Park Open Space and Sanctuary Park, and the City is treating them with HCA. Sanctuary Park is at 27 Sanctuary Drive in Dundas. The City is using IMAjet 10, which replaces TreeAzin, the product it used in its 2024 and 2025 treatments with the Royal Botanical Gardens. According to the update, injecting into the trunk keeps more of the product out of the surrounding environment than other ways of applying it. In an October 7 post on its Bluesky account, the City said the work started October 5 and would take about two weeks.

The Rules Apply at the City Line

Treating trees protects them where they stand. The federal rules deal with the other way the insect spreads, which is people carrying wood and greenery from place to place. A CFIA Infested Place Order dated August 21, 2025 added Hamilton, Niagara Region, Haldimand County and the Township of Alnwick/Haldimand to the infested area. The regulated area covers all of the City of Hamilton, so Dundas is inside it, along with every street and backyard within the city limits.

The CFIA's regulated areas page lists these items as ones that cannot be moved out of a regulated area without approval:

• Hemlock, yeddo spruce and tiger-tail spruce, including:
  • plants for planting, such as nursery stock and other plant parts
  • forest products with bark attached, such as logs, lumber, bark chips and wood mulch
  • dried branches
  • Christmas trees
  • fresh decorative wreaths, foliage and branches
• Firewood of all species

The firewood line is the broadest one. It covers maple, oak and every other species, not just hemlock. A trip from Dundas into Burlington, or up to a cottage outside Hamilton, crosses that boundary. The CFIA asks anyone who needs to move regulated material out of the area to contact their local CFIA office first. This is general information, not legal advice. Before moving wood or greenery out of Hamilton, check the specifics with the CFIA directly.

Where to Look on a Winter Walk

The next few months are the season for spotting the adelgid. A few HCA notices also affect valley trails this week. As of October 21, these were the posted alerts for the Dundas Valley Conservation Area, whose main lot is at 650 Governors Road:

1. Murray Ferguson Trail: Sections are closed October 26 to 30 for what HCA calls ecological restoration work, with heavy equipment and forestry contractors on site. Users are asked to follow the detour routes.
2. Old Rifle Range off Headwaters Trail: Forestry contractors were scheduled to work here October 26 to 28. Headwaters Trail itself stays open.
3. Sawmill Pond: The trail around the pond has been closed since October 7 because of bank instability. No reopening date has been posted.

HCA takes alerts off the page once they no longer apply, so the current alerts page is the best place to check before you head out.

Once you're on the trail, HCA's own survey tells you where to look. Hemlocks grow mostly on north-facing ravine slopes near water, and those creekside trees are the ones the year-one treatments target. The Ontario government says to look for white woolly sacs at the base of the needles on new branches. Other signs are needles dropping early, buds and shoots dying back, and a crown that is thinning and turning grey. The Royal Botanical Gardens says the adult insects can look like flakes of black pepper.

The same signs apply to hemlocks on private property. The City's 2026 program covers the 174 trees on City land at its two parks. HCA's program covers the conservation area. If you think you've found the adelgid, the CFIA has an online form for reporting a hemlock woolly adelgid sighting. HCA's guidance sends suspected sightings to the CFIA or to EDDMapS. RBG recommends citizen science platforms such as iNaturalist. A photo of the underside of a twig, taken in March when the sacs are easiest to see, makes a far more useful report than a description from memory.

If mature trees are part of what you value about your property in Pleasant Valley, and you'd like help finding a qualified professional to look at your hemlocks, Jessica Alexopoulos & Associates can connect you with trusted local referrals. Get in touch whenever it would be useful.