How to Control Tent Caterpillars

The Western tent caterpillar is a native insect with a habitat that ranges from Coastal and Interior of British Columbia to California.

The tent caterpillar's population cycles naturally every 5 to 10 years. Its numbers are kept in check by a parasitic fly, predators and disease. This year, the Western tent caterpillar is relatively high in numbers in Greater Victoria.

The City of Victoria removes tent caterpillars' nests from trees under five years of age on boulevards and in City parks to prevent damage.

Damage to mature trees is primarily cosmetic in nature (e.g. chewed leaves) and most mature trees can withstand high levels of tent caterpillar activity.

Tips for Homeowners

Below are some tips for homeowners who wish to remove tent caterpillar nests from their trees:

  • Prune out only those nests that won't cause structural damage to the tree and minimize the amount of wood removed.
  • Kill removed tent caterpillars either by submerging them in soapy water or stomping on them prior to disposing them in a compost bin.
  • Do not place living caterpillars into the garbage as they have the ability to eat their way out of the garbage bag.

Tent caterpillars have numerous enemies. One is a tachinid fly which parasitizes the larvae by depositing white eggs on the caterpillar's body. When the egg hatches, a small maggot burrows into the caterpillar and begins feeding. This eventually destroys the caterpillar. Leaving infected caterpillars on mature trees helps to make sure that the parasites will survive and keep caterpillar numbers down.

Note: The white circles in the photo below are the helpful parasite eggs on the caterpillars.

 


For more information, contact the City Parks Division at 250.361.0600 or email City Parks.