Mississauga begins aerial spray to control tree-killing insects

May 12, 2022

By: The Working Forest Staff

The spray is meant to control caterpillars that feed off a variety of trees before eventually turning into moths that then begin the cycle again.

CAPTION: Mississauga’s aerial spray program begins early next week in an effort to save the city’s tree canopy.

Low flying helicopters are scheduled to be out in the early hours of May 15 with the program continuing at various intervals until the middle of June.

Mississauga has deemed the program necessary as the insect (formerly called the gypsy moth caterpillar but now known as the spongy moth or the LDD moth) feeds off leaves which can lead to the killing of trees at an alarming rate. The spraying is done in the spring with the hope that it will kill larvae and caterpillars before they turn into moths.

The aerial spray program is expected to protect hardwood trees like maple, oak, elm, ash, poplar, willow and birch.

While the City has used other methods to control the population of the insect, the spray has been determined to be the most effective weapon.

The insecticide used is called Foray 48B, containing the active ingredient Bacillus thuringiensis subspecies kurstaki (Btk).

The spray produces fine droplets that are small enough to stick to the leaves of trees. Btk is a naturally occurring bacterium found in soil and has been approved by the Pest Management Regulatory Agency, an agency of Health Canada, for aerial use over urban areas.

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