Forest Tent Caterpillars

The RM of St. Clements does not spray Forest Tent caterpillars.

Find more information about Forest Tent caterpillars on the province’s website.


Forest Tent (Malacosoma disstria)caterpillar facts

  • They are a native insect
  • Caterpillars (or larvae) prefer to eat trembling aspen but will eat any broad-leafed tree or shrub
  • Widespread outbreaks happen approximately every 10 years, usually lasting three to six years. Feeding ranges from a light thinning of the tree top to trees completely stripped of their leaves
  • Usually the trees don’t die, and the leaves grow back later in the season
  • If the tree is stripped of its leaves for two or more years, it will weaken and can eventually die
  • They are the only tent caterpillers to use a nomadic foraging strategy – meaning they move to new and distant locations
  • They feed for 5-6 weeks



  • Do nothing as the trees usually survive
  • Place barriers on trees like sticky bands
  • Remove egg masses before they hatch
  • Remove larvae when congregated
  • Apply Bacillus thuringiensis, a natural, soil dwelling bacterium particularly effective on inch worms of all types.
    • Use easily applied spray to hit worms and protect the leforest-tent-caterpillar-mothaves at the first signs of damage. BTK sprays do not harm honey bees or birds and are safe for use around pets and children.