Dealing with Gypsy Moths


Gypsy moth (Lymantria dispar) is an invasive species that is severely weakening trees across North America.  Unfortunately, parts of Middlesex Centre are experiencing an infestation of gypsy moth.

What happens during an infestation?

Gypsy moth outbreaks occur every 7 to 10 years. Gypsy moth caterpillars (“larvae”) will chew holes in leaves, and may partially or totally strip a host tree of its leaves.

During outbreak years, nearly all broadleaf (hardwood) trees may be completely defoliated. This can harm and even kill otherwise healthy trees. Caterpillars appear everywhere and their droppings ("frass") will fall from the trees. 

This species is known to infest trees in woodland or suburban areas. They prefer to infest hardwood species, such as oak, birch, poplar, willow, maple and others.

What does a gypsy moth look like?

Photos courtesy of Ontario's Invading Species Awareness Program

Gypsy Moth Caterpillar

Caterpillars are 5-6 centimetres long with five pairs of blue dots and six pairs of bright red dots along their back.

Gypsy moth with egg sack

Female moths are white with dark markings and cannot fly. Male moths are brown and can fly. Females are larger than males with a 5 cm wing span, males only span 2.5 cm.

Egg masses are about 4 cm long, tan colored, and can be found on tree trunks, furniture, buildings, etc. You may see spongy egg masses on the trunks and branches of infected trees beginning in late July.

Where are gypsy moths found in Middlesex Centre?

While they can be found anywhere in Middlesex Centre, there is a particularly heavy infestation in the Westbrook Park area in Kilworth.

Map of gypsy moth infested area in Kilworth

What is Middlesex Centre doing about gypsy moths?

We are working with a local arborist to treat the municipal portion of the tree lot at Westbrook Park in Kilworth.  Based on the advice of the arborist, we anticipate the treatment will begin once the eggs hatch and the caterpillars climb to the top of the tree (in the canopy).  This is the best management practice for treating heavily infected trees. 

  • Treatment Period: June 10, to June 17, 2020 (exact dates may vary depending on weather)
  • Area to be Treated: The Middlesex Centre Treatment Area marked on the map above.
  • Product to be Used: Davey Tree will be applying a biological insecticide called Bacillus thuringiensis ‘kurstaki’, or Btk for short. (For more information on this product, please see the letter attached).
  • Notification: The area will be signed as per provincial requirements, and notice will be posted under “Public Notices” on the municipal website.

What can homeowners do to control gypsy moths?

For homeowners in the heavily infested area near Westbrook Park

Homeowners are responsible for managing gypsy moths on their property.  As mentioned above, the municipality is working to treat the trees on municipal property in the Westbrook Park area.  As this involves bringing in specialized equipment from out of the area, we asked the arborist to provide a flat rate per household for treating individual properties.

Participating in this “bulk” treatment purchase is optional, but we hope that many of homeowners will consider the opportunity. 

The more homeowners that treat their trees, the better the outcome for all neighbouring properties.

A letter with additional information will be delivered to your home if you are in the affected area. You can find the letter at the bottom of this page as well.


Other municipal homeowners

Homeowners are encouraged to monitor their hardwood trees like oaks, maples, beech and walnut for the presence of gypsy moth caterpillars. 

solutions and Treatments

Here are some general recommendations for dealing with gypsy moths on your property:

  • Keep your trees in good health.
  • Install sticky bands to monitor and control caterpillar populations and/or install pheromone traps in trees to lure and trap male moths to prevent them from mating with female moths. Consult your local nursery or hardware store for information on these bands/traps.
  • Use burlap bands. As the weather warms in late May and June, caterpillars tend to feed at night, and climb down the tree to shelter from the heat during the day. Wrap burlap or light-coloured cloth around tree trunks to collect the caterpillars. Fold the burlap back over itself to create a cavity, and the caterpillars will collect in there. Once a day, scrap the caterpillars off the burlap into a bucket of soapy water, then re-apply the burlap. This will help reduce the number of caterpillars in your tree. This technique may also be used later in the summer to collect female moths (which are unable to fly and so will climb up the tree to lay their eggs.)
  • Physically remove and destroy egg masses. This is one of the best ways to reduce the infestation - every egg mass removed will reduce the population by several thousand!  Use a small paint scrapper or other gentle tool to remove the egg masses. Soak the egg masses in soapy water overnight to kill them, and then they can be bagged and sent to the landfill. Don’t drop them on the ground or put them in your composter as the caterpillars will still emerge.  See the City of London’s video to see how to remove the egg masses. The best time to remove the masses is in the fall after the leaves have fallen. Try to avoid windy days if possible.
  • Contact an arborist if you think a tree on your property is being heavily defoliated by gypsy moths. Insecticide treatments may be necessary.
  • Contact the municipality if you think a tree on municipal property is being heavily defoliated by gypsy moth. Please include the street address in your message.

Learn more

Information for this article was taken from the following websites:

Additional information sources:



If you have questions regarding the municipality's response to gypsy moths, please contact Scott Mairs. (Email is preferred as phone access is limited at this time.)