News release

City Develops 2018 Invasive Insect Mitigation Program

City services | November 22, 2017

Today Council approved the 2018 Gypsy Moth and Fall Cankerworm Mitigation Program corporate report. Last week at General Committee, staff from the City’s Forestry section presented recommendations, which included funding for aerial sprays in spring 2018, an additional mitigation measure to help with infestations of invasive insects. The $1.6 million aerial spray program, funded by the City, will target gypsy moths and cankerworms on both City and private property in specified areas forecasted for severe defoliation.

“Last year, we experienced an unprecedented infestation of cankerworms across Mississauga. The infestation put a lot of strain on many of our older hardwood trees such as oak, elm and maple,” said Laura Piette, Director of Parks and Forestry. “We also need to address the growing gypsy moth population to ensure the long-term health of our trees in Mississauga. This will avoid putting more stress on our already fragile tree canopy in the identified area.”

Fall cankerworm caterpillars emerge in the spring and often strip trees of their leaves as they feed. This makes trees more susceptible to disease and damage from other insects and extreme weather.

Piette added, “To protect our City-owned assets and to help control the expected increase in insect population, we’re putting forward proactive measures that include aerial spraying to treat severely impacted areas.

The gypsy moth data forecasts severe tree defoliation in the identified areas. Cankerworm data is being collected now and will help define a more exact aerial spray area.

“Data models and forecasted growth populations suggest we’re going to see a spike in both cankerworms and gypsy moths over the next year,” said Jessica Wiley, Forestry Manager. “We are using a Bacillus thuringiensis (Btk) spray program. It’s an approved product by Health Canada that is used to help control both gypsy moth and cankerworm infestations; however, it’s safe for humans and all other wildlife. We’ve used Btk in the past and have seen success spraying it roughly 10 years ago to manage gypsy moth infestations across the city.”

Staff recommended that Zimmer Air, an experienced Thunder Bay-based company with specialized equipment be procured to conduct the spray. Zimmer Air also successfully carried out the City’s 2006-2007 aerial spray and has been used by other local municipalities. The aerial spray program will occur in spring 2018 and a communication plan is being developed to ensure residents in the area receive timely information.

The City is also working with other municipalities who have indicated an interest in a joint aerial spray program.

Staff will begin implementing the plan in early 2018.

To learn more about invasive species in Mississauga, visit

For updates regarding fall cankerworm and gypsy moth management, visit


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