Tent Caterpillars: Tolerance is the Key

Tent Caterpillar
Photo courtesy WSU

(My father used to use a blowtorch on tent caterpillar nests. The City of Lake Forest Park advocates a different approach - Ed.)

Spring is here and so are the Tent Caterpillars. They have begun eating the tender spring foliage of the deciduous trees and shrubs; especially alder, willow, fruit trees, and roses.

Fortunately, healthy plants and trees have the ability to survive and regrow leaves during the same season. Tent caterpillar infestations tend to eventually collapse on their own as trees mobilize their defense systems and natural enemies destroy the caterpillars.

As a result, control measures are only necessary when the caterpillars attack young or stressed plants that may not be able to recover from defoliation.

Control measures are only considered when tent caterpillars are attacking young or stressed trees. In this case, hand-pruning or picking the tents from branches is the best option. This is best to be done in the early morning or evening when the temperature is cool and the caterpillars return to their tents. You can then put the pruned tents in a bucket of soapy water or seal them in a bag and throw away in your garbage. Another method of control is to hand-strip egg masses or prune them out of plants during the winter. 

Chemical control is not recommended as this may harm beneficial insects, birds and other wildlife. Burning the tents from the trees is also not recommended as it damages the tree and is a serious fire hazard.

Tent caterpillars are certainly unpleasant but are part of the natural ecological process. Your best option is to tolerate the infestation and allow the natural predators and parasites including many garden birds, wasps and ground beetles to manage infestation. It may take a few years so please be patient.

For additional information check out the following websites:

• Washington Toxics Coalition Fact Sheet
• Home Garden Series Washington State University