Caterpillars

Caterpillars are immature moths and butterflies.

Though caterpillars feed on plants and can chew irregular holes or entire leaves, they are primarily a nuisance rather than a serious threat to your plants. Healthy plants can handle some caterpillar damage. Many caterpillars are food sources for birds, and many adult moths help pollinate your plants.

Tent caterpillars are a common problem in western Washington. There are several types, all of which form large silken webs or “tents” in the foliage and branches of trees. Some species mature in fall and some in spring.

What you can do

• Watch for tents in your trees. Early removal of tents minimizes damage and reduces the likelihood of the pest spreading to other branches or trees.
If you notice caterpillar tents in your trees, you can:
• Remove the tents by hand; this is easiest in small trees. You can roll the tent out of the foliage, or cut out branches containing nests.
• Call In Harmony to control the caterpillars for you.

What In Harmony can do

• Remove the tents by hand for you.
• Apply organic pesticides. In cases where infestation is severe, In Harmony may recommend treatment with pyrethrums, organic pesticides derived from chrysanthemums, to exterminate caterpillars. We take this action only when necessary because of two drawbacks:
• While pyrethrums are safe, organic products that pose no long-term environmental harm, any pesticide is a poison and can harm people, animals, and desirable insects when contacted by direct spray or mist before they break down.
• The treatment stops the caterpillars from eating your plants, but the unsightly nest remains in the tree until wind, rain, and time knock it down.

References

Tent Caterpillar. Pro IPM: Integrated Pest Management Solutions for the Landscape Professional, Green Gardening Program. Phillip Dickey.
Biology and Control of Tent Caterpillar. Washington State Cooperative Extension. Collman, S.A. and Antonelli, A.L. http://gardening.wsu.edu/library/inse003/inse003.htm, November 17,2000.
Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide. Dreistadt, S. ANR Publications, University of California, 1994.