News release

City’s 2018 Aerial Spray Program Takes Flight to Prevent Tree Loss

City services | March 21, 2018

The City of Mississauga is conducting an aerial spray this spring. The spray will help to manage high levels of fall cankerworm and gypsy moth caterpillars and prevent tree loss. The seasonal spray window is set for April 23 to June 10, 2018, between 5 and 7:30 a.m. The spray area consists of private and public land in Wards 1, 2, 6, 7, 8 and 11 and is roughly 1,940 hectares (4,794 acres), equivalent to approximately 1,552 football fields.

“The tree canopy is an important part of Mississauga, providing countless benefits to the community and environment. Preserving, protecting and growing the tree canopy remains an important focus for the City,” said Jodi Robillos, Acting Director of Parks and Forestry at the City of Mississauga. “Over the last few years, the City has been able to control fall cankerworm and gypsy moth caterpillar populations using Integrated Pest Management (IPM) measures, such as tree banding, tree injections, ground spraying and egg scraping. However, in certain areas of the city, these methods alone are no longer sufficient. We’ve put forward a comprehensive plan that will treat areas expected for severe leaf loss.”

As fall cankerworm and gypsy moth caterpillars begin to grow, they eat a lot. They have the ability to strip trees of all of their leaves, leading to tree weakness and potential disease.

“Based on data collected for fall cankerworms and gypsy moths, 2018 populations are expected to increase in a few areas of Mississauga, mostly along the Lake Ontario shoreline and Credit River Valley,” said Jamie Ferguson, Aerial Spray Project Lead for the City of Mississauga. “The City opted to conduct an aerial spray treatment as an effective and proven method for controlling fall cankerworm and gypsy moth populations. This is in addition to implementing other Integrated Pest Management measures. Spray dates are dependent on leaf and caterpillar size and weather conditions. Past records indicate the spray will most likely occur in the first two to three weeks of May.”

The City has contracted Zimmer Air Services to implement the spray. The spray will happen over a three-day period, with a total of two spray applications being completed. Two helicopters will fly about 15 to 30 metres above the treetops to complete the spray. Spraying is weather dependent and will only be done under the right conditions. As a result, specific spray dates are chosen 48 hours in advance and can be cancelled if weather conditions change. The City will issue communications to the public 48 hours before each treatment and provide up-to-date information through 3-1-1 and online at The spray may be cancelled up to 12 hours in advance if weather conditions change.

The aerial spray will use the biological control treatment Bacillus thuringiensis subspecies kurstaki (Btk). The spray will produce fine droplets that are small enough to stick to 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. Btk is an effective pesticide that has been has been used globally for more than 30 years to successfully manage cankerworm and gypsy moth caterpillar populations.

“The Region of Peel – Public Health does not expect any human health impacts from Btk aerial spraying,” said Dr. Jessica Hopkins, the Region’s Medical Officer of Health. “While no special precautions need to be taken, residents may consider remaining indoors, washing their hands, covering lawn furniture, pools, BBQs and rinsing with water after the spray.”

In 2006 and 2007, the City conducted an aerial spray program to mitigate gypsy moth populations. Since then, the City has continued to monitor and manage pests for City-owned trees. The total spray area in the 2006/2007 program covered approximately 800 hectares, the majority of which was City-owned parkland and woodlots.

The City has been working with other municipalities (Oakville and Hamilton), Regional partners (Peel Public Health and Peel Regional Police) and Provincial agencies (Ministry of Transportation, Ministry of Natural Resources and Forestry, Ministry of Environment and Climate Change) to finalize spray details.

In the weeks leading up to the spray, residents in the defined spray zone area will be contacted by the city with further details.

To find up-to-date information on how to control fall cankerworms and gypsy moths on your property, aerial spray details such as road closures, spray dates, times and locations, call 3-1-1 or visit to also sign-up for email alerts. Residents with specific medical or health concerns regarding the spray can call Peel Public Health at 905-799-7700.

Parks and Forestry staff recommended an aerial spray program be implemented where severe defoliation was expected. This recommendation was adopted at Council on November 22, 2017. The $1.9 million aerial spray program, funded by the City, will target fall cankerworm and gypsy moth caterpillars on both City and private property in specified areas forecasted for severe defoliation.


Media Contact:
Karen Flores
Senior Communications Advisor
City of Mississauga
905-615-3200, ext. 5053
TTY: 905-896-5151