Tent Caterpillars





What is a Tent Caterpillar?

Tent Caterpillars (Specifically Easter Tent Caterpillars in Canada) get their name from the fact that their nests look like tents.  When the young hatch from their eggs they gather together in the branch of a tree and spin a tent out of silk.  This silk tent is used as protective housing for the caterpillars to gather in during cool nights.  During the day, tent caterpillars will leave the safety of the nest to feast on the leaves of the surrounding tree.  Tent Caterpillars are the most destructive caterpillars in North America, capable of stripping trees completely bare.

Tent Caterpillars will be seen during the spring when eggs laid the previous fall hatch into young caterpillars.  While there are tent caterpillars hatching each summer outbreaks occur approximately every 10 years in Canada.  Outbreaks can last up to two years and cause severe damage to trees.

What to look for:

In the Spring you will see obvious sign of a tent caterpillar infestation.   First is, of course, the tent-shaped nest as seen pictured on the left.  Other signs will be defoliation of the trees in your yard or field.  In the summer, look for tough, yellow-to-white cocoons on tree trunks, fences, debris and sheltered areas. In the fall, look for shiny, dark brown saddle-like cases which straddle or encase twigs of trees which are known to be susceptible to tent caterpillar infestations. 

Controlling Tent Caterpillar Populations:

Nimby Pest Management will destroy egg-cases and cocoons via removal and, if necessary, burning of the nests and/or cocoons.  If the tents are too large it may be necessary for your Nimby Professional to cut off the infested branches and burn or crush individual webs.

Biological Control
The bacterium B.t. (Bacillus thuringiensis), is a selective biological insecticide. After ingestion of vegetation treated with B.t., caterpillar larvae cease to feed and die within five days. Insects which do not have a larval stage in their development are not affected by B.t. Products which contain this bacterium are also non-toxic to mammals, birds and fish. 

Chemical Control
If an infestation of caterpillars is suspected, a dormant oil spray may be used on susceptible trees in late winter to smother the eggs before they hatch in early spring.

Products which contain methoxychlor, carbaryl, permethrin and resmethrin are registered for control of tent caterpillars. If the tent is within reach, break it open with a stick and direct the insecticide into it. Spraying is most effective in the evening, as the caterpillars return to the nesting area at night.