Western tent caterpillars back en masse this spring

Bellingham HeraldMay 10, 2013 

Wiggling masses of white-orange-and-black caterpillars are emerging from their silken nests to munch on tender leaves - signaling a second spring when Western tent caterpillars might be out in big numbers.

"I have seen them out. They're not as bad as last year. What I'm guessing is we're getting a resurgence of a population that peaked last year," said Chris Benedict, agriculture agent at the Washington State University Extension office in Whatcom County.

"Though they'll be out, they'll be less of an issue than last year," he added.

The native caterpillars are considered a nuisance but largely harmless. They are the larvae form of brown, stubby-looking moths that will emerge from cocoons later in June or July to mate and lay eggs.

Population booms are cyclical.

The caterpillars hatch from eggs over-wintering on tree branches. Once they hatch, they start eating.

They prefer the foliage of most deciduous trees and shrubs such as alder, roses and fruit trees.

And while the hungry caterpillars put a visible dent in the surrounding greenery - which people find unsightly, along with the masses of worms - they usually don't kill the healthy trees they feast on, according to gardening experts.

But small trees might not be able to recover from such defoliation.

The WSU Master Gardener program has been fielding questions from the public.

"We've been seeing folks bring in some young tent caterpillars wanting to know what they are and what to do about them," said Beth Chisholm, master gardener and coordinator of the Community First Garden Project through WSU Extension.

She said people shouldn't be "too alarmed."

If people want to get the caterpillars off their fruit trees, Chisholm recommended they cut off the infested branch, put it in a bag, tie it up and put it in the garbage.

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