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Aerial Gypsy Moth spraying coming to Halton


Aerial Gypsy Moth spraying coming to Halton

Conservation Halton (CH) is preparing to spray a biopesticide using two aerial applications over areas that are predicted to be infested with invasive gypsy moths between May 14 and June 14, 2021. Actual dates will be selected 24 to 48 hours in advance as spray applications are weather dependent. The second application will take place five to seven days after the first application.

Survey results from Fall 2020 have shown that gypsy moth populations are expected to be extremely high this spring. The four CH properties that will be treated are Mount Nemo Conservation Area in Burlington, Sixteen Valley Conservation Area in Milton, Waterdown Woods Conservation Area and Clappison Escarpment Woods in Waterdown.

The biopesticide that will be used for the spray is Foray 48B. The active ingredient, Bacillus thuringiensis subspecies karstaki (Btk) is a naturally occurring bacterium found in soil. It has been used in Canada for over 50 years to control pests, including gypsy moths. Studies have shown that no toxic effects have been demonstrated in humans, mammals, fish, birds, or other non-Lepidoptera insects such has honeybees. The activation of Btk toxins require alkaline conditions that exist only in the digestive systems of certain insects.

The European gypsy moth is a non-native defoliating insect that was introduced to North America in 1869 and was first discovered in Ontario in 1981. Gypsy moths larvae feed rapidly on the leaves of both deciduous and coniferous trees. During the larval stage, a single gypsy moth caterpillar can eat an average of one square meter of leaves making them highly destructive to local forests. The defoliation of the trees makes them more vulnerable to disease, other insects, and environmental stressors.

Health Canada states that no special precautions are necessary or required when spraying Btk. However, those with concerns can reduce exposure by staying indoors with windows and doors closed when Btk is being sprayed in their neighbourhoods. Once selected, dates will be posted on Conservation Halton’s Facebook, Twitter, and website. If members of the community wish to be alerted directly when the spray is taking place, please e-mail

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