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GRCA to spray to control gypsy moth caterpillar population

It's expected to happen between May 20 and June 10
gypsy moth caterpillar
Stock photo

The Grand River Conservation Authority (GRCA) will be spraying an organic pesticide at a number of its properties this spring to control growing populations of gypsy moth. Aerial applications by helicopter are planned over susceptible forest areas at Pinehurst Lake, Brant and Byng Island conservation areas, as well as at the Dryden Tract and the FWR Dickson Wilderness Area. Control of the current outbreak is required to protect and maintain affected forest areas and to reduce future hazard tree removals.

The organic insecticide Foray® 48B, whose active ingredient is a widely distributed soil bacteria called Bacillus thuringiensis kurstaki (Btk), will be applied by helicopter. Two applications will occur approximately three to seven days apart. Timing depends on insect and tree development, as well as weather conditions. It is expected that applications will occur between May 20 and June 10, 2020.

All GRCA properties and facilities are currently closed due to the COVID-19 pandemic. Members of the public are reminded to obey all closures. It is important that people are not present during aerial spraying for safety and regulatory requirements related to low level flying. Should properties re-open prior to the aerial spraying, appropriate measures will be taken to close the areas forpeveral hours while the spraying occurs, and to communicate this information to the public.

Btk insecticide is not considered a human health risk and is not toxic to bees and other insects, birds, fish, mammals or adult moths and butterflies. Its application won’t impact moths and butterflies, like monarchs, whose caterpillars develop later in the season. Btk insecticides have been in use for over 30 years in Canada and around the world. Their use is approved by Health Canada including for aerial applications over urban areas.

About gypsy moth

Gypsy moth (Lymantria dispar) is a highly cyclical, non-native forest pest. Their caterpillars eat the leaves of a wide variety of trees. High populations of gypsy moth result in tree defoliation with significant potential impacts on tree and forest health. Ecological impacts result from tree declines and mortality, especially in oaks and hickories, which provide valuable food and habitat for a wide diversity of species. The current gypsy moth infestation is also having a cumulative forest health impact on areas that have recently undergone significant tree losses due to emerald ash borer. More information and updates on the project can be found online at


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