Hemlock Woolly Adelgid

Hemlock Wooly AdelgidThe Hemlock Woolly Adelgid initially invaded the United States in the 1920’s. This introduced insect from Asia has been working its way up the east coast and arrived in Connecticut with Hurricane Gloria in 1985.

Adelgids have already defoliated and killed large numbers of native Canadian hemlock trees throughout American forests. Adelgids are cool weather insects and well adapted to the New England climate, which means you can find adult adelgids anytime of year. They are globular masses of cottony/waxy tufts, resembling the end of a q-tip, and found on bark, foliage and twigs.

Adelgids cause hemlocks to weaken and eventually die. Infested trees first begin to look thin with a lighter green color. This happens because the insects feed by sucking sap from twigs and foliage causing the trees to become weak and the needles to fall off. A serious infestation can defoliate the tree in a year to eighteen months.


There are three ways to control the Woolly Adelgid:

  • The non-toxic horticultural oil is the most effective, but timing is crucial. It is sprayed twice a year, once in early spring and once in early fall. The oil works by smothering the insects.
  • The environmentally friendly soap, called M-pede (FactsheetMSDS), is effective if the adelgid is discovered after the proper timing of applying the horticultural oil. This product is applied late spring or late fall.
  • Tree Injection with ArborjetA systemic injection of imidacloprid, a low toxicity pesticide, with the Arborjet microinjection system, is used if a tree is unable to be sprayed or the timing has passed for the other treatments. The injection goes directly into the sap flow of the tree, does not contaminate the air or the soil or harm the tree. There is a two to three year residual and the injection can be done in spring, summer and fall. This method has proven to be quite effective in controlling the adelgid when the other methods are unable to be used


For an inspection of your hemlocks, recommendation for treatment, or cost, call or email Boston Tree Preservation.  Timing is crucial for effective treatment.  Neighborhood discounts are available.  We service the Greater Boston and 495 loop.


Sorry, you can not to browse this website.

Because you are using an outdated version of MS Internet Explorer. For a better experience using websites, please upgrade to a modern web browser.

Mozilla Firefox Microsoft Internet Explorer Apple Safari Google Chrome