Forest Tent Caterpillars

Tent caterpillars hatch near time of bud break and feed through May and June for five to six weeks.

They first feed on growing flower and leaf buds in host tree crown and then next feed on foliage, usually one branch at a time.

The forest tent caterpillars can be sprayed with a number of pesticides, with the most common being Malathion or Sevin. Please check with your local garden centre and be sure to follow proper application instructions. Home remedies such as insecticidal soaps or dish soap and water can also be used, but multiple applications will be needed.

The City of Warman uses an environmentally friendly spray called BTK. BTK is not harmful to people, animals, birds, bees or any insect that is not in the larval (caterpillar) stage of their life cycle.

However, no spray is 100% effective and there WILL BE caterpillars in and around the City of Warman despite the best efforts of the Parks Department.

The City of Warman Recreation and Community Services encourage residents to inspect their trees for forest tent caterpillar egg sacks that appear as a ball of bark on three limbs, it can be scrapped off and disposed of. Spaying your trees as mentioned above is also very helpful.

Here are a few things to keep in mind:

  • Yes, they are gross. But they will not hurt you. They do not sting, they do not bite, they are not poisonous, and they are just plentiful.
  • Their caterpillar stage is short-lived. They'll only be bad for a couple of weeks, and by mid-June, they will be only a memory. They will emerge from their cocoons in late July and their moth stage only lasts five to 10 days.
  • They will defoliate trees and shrubs, in some cases almost completely. However, our vegetation is very hardy and new leaves will appear. By July, the trees will be almost fully refoliated.
  • This defoliation will not hurt healthy trees. Healthy trees would need to be severely defoliated for four or more consecutive years before the tree would be at risk. Which leads us to...
  • These caterpillars are cyclical. Outbreaks like this happen approximately every 10 years (though can be anywhere from six to 16 years) and usually last about three years.

The City of Warman Parks Department will do their best to remove them, but keep in mind that they WILL re-congregate in those places, and over the next couple of weeks, it may simply be impossible to keep an area completely free of them.