Fall Cankerworm Ground Spray Program
Based on monitoring conducted in 2016 by the City’s Forestry team, the population of fall cankerworm appears to be on the rise in certain areas of the City. As a
result, the City will be conducting a ground spray program (the tree canopy will be sprayed from the ground) on City-owned oak trees (marked with a pink dot on road side) in
impacted neighbourhoods. Additional control measures will be implemented in parks and woodlots where ground spray would not be effective.
The areas of higher cankerworm
population correspond to areas that have gypsy moth populations as well. Bacillus thuringiensis subspecies kurstaki (Btk) will be used in the ground spray
program to treat for cankerworm in Mississauga. Btk is also effective against gypsy moth so we anticipate an impact to both populations of these insects this year in
the key neighbourhoods identified.
We will continue to monitor populations City-wide throughout 2017.
Residents may find tree banding as
a tool in reducing the number of cankerworms on your trees. We recommend that residents contact a tree or lawn care company for guidance on dealing with cankerworms on their
Frequently Asked Questions
The fall cankerworm is a defoliating insect native to North America that can become a major pest during
The caterpillar eats the leaves of trees, making them more susceptible to
disease and/or damage from other insects or extreme weather. It is important to note that cankerworms won┐t hurt healthy trees. Many trees that lose their leaves will recover
later in the season.
Fall cankerworm caterpillars are most commonly found on
hardwood species such as oak, maple and elm.
There are several insects such as parasitic wasps which destroy the moth eggs
and some bugs such as ground beetles and the spined soldier bug that eat the caterpillars. Several bird species such as chickadees and robins will also eat cankerworm
Fall cankerworms naturally occur every 10-15 years and last for 2-3 years. In spring,
caterpillars hatch around the same time that new leaves are emerging. They feed for 5-6 weeks and then drop from the trees on silk strands and spend the next 6 months of their
lifecycle underground. The adult moths emerge from the soil in November or December and lay eggs in the tree canopy.
The City is currently groundspraying City-owned street trees with a safe,
biological control called Bacillus thuringiensis subspecies kurstaki (Btk) to reduce the cankerworm population. On trees not receiving a ground spray treatment,
the City is using a sticky band to catch the caterpillars before they climb up the tree.
Residents may find tree banding as a tool in reducing the number of cankerworms on your
trees. We recommend that residents contact a tree or lawn care company for guidance on dealing with cankerworms on their property.
No, there have been many scientific studies performed on Btk use and the possible effects and it has
been deemed safe. It is a bacteria and is often sprayed on crops that are labelled organic because it isn┐t a chemical.
No available information has demonstrated that it is harmful. In fact, some scientific
journal articles suggest that trees can more easily absorb the nitrogen produced by the caterpillar excrement so it helps them grow in some cases.
Downtown Ash Tree Removals
Beginning April 2017, Forestry staff will be removing 78 dead ash trees from the downtown core that have been infested with Emerald Ash Borer.
Forestry staff will be removing 78 dead ash trees from the downtown core that have been infested by Emerald Ash
Borer. Trees to be removed have had an orange "X" painted on them. Once these trees have been removed, their stumps will be removed or temporarily covered over with
Replacement trees will be planted for all 78 trees removed. However, due to construction of the forthcoming Hurontario-LRT,
some replacement trees will be planted in alternate locations.
In certain instances and locations, the City will be implementing soil cell technology to give trees the soil volume they need to thrive, allowing their roots to spread under
the sidewalk or parking space.
These ash trees have been infested by Emerald Ash Borer. Once infested by EAB, an ash tree dies quickly—leaving a
dead or dying tree that poses safety risks.
Work will take place in the City Centre area of Ward 4 near the Square One Shopping Centre in the following locations:
- City Centre Dr between Confederation Pkwy and Living Arts Dr;
- City Centre Dr between Kariya Gate and Robert Speck Pkwy; and
- Rathburn Rd W between Confederation Pkwy and City Centre Dr.
Forestry staff plans to conduct work outside of morning and afternoon rush hour to avoid impact on traffic.
Updates on this project will be posted on this webpage and will also be shared on our Twitter, Facebook and Instagram social media channels.