Nov 08th, 2016

If you notice something is snacking on your tree’s leaves, you could have a Forest Tent Caterpillar infestation. These pests are the most widespread defoliators of deciduous trees across Canada, and occasionally they invade in massive quantities. Their favourite food is the leaves of Trembling Aspens, but they will also go after beech, apples, basswood, cherries/plums, birch, ash, oak, maple, elm and willow. During severe infestations, they will feed on almost any green leaf they can find.


The caterpillars are black, hairy and about 3 mm long when young. When mature, they are about 50 mm long with wide blue bands along the sides of their bodies and whitish spots running down their backs. The young caterpillars clump together on the tree’s trunk or branches when they are not feeding. In late June, females lay 150 to 350 eggs in clusters or "egg bands" that encircle twigs. These clusters are spongy, brownish masses and are easy to spot on small branches and twigs in the fall.

Best care practices

Heavy defoliation for two or more years can negatively affect the health of your tree and leave it susceptible to attack by other pests or diseases. To help control the caterpillar, remove egg bands in the fall when they are easiest to find. This can be done by scraping them off with a dull blade. In the summer, the caterpillars can be removed through pruning, spraying down the tree with a strong jet of water, or by hand.

Interesting Facts about Bronze Leaf Disease

  • The first outbreak in Canada was recorded in 1791.
  • The Latin name is Malacosoma disstria.
  • They are Phyllophagous, which means they feed on the leaves of plants.

« What's Going On With My Tree? Bronze Leaf Disease