Steamboat Springs Entomologists at Colorado State University have identified the species of caterpillar that has exploded across Routt County. The caterpillar, which has been feasting on the leaves of aspen, scrub oak, sarvis and chokecherry trees, is known as a linden looper.
C.J. Mucklow, director of the Colorado State University Cooperative Extension Service Office in Routt County, said there have been several infestations of the linden looper across western Colorado. The caterpillars were first reported in Routt County early last week, with most calls coming from South Routt to west of Craig in Moffat County.
Mucklow said he does not recommend treating the caterpillars with insecticides because they should soon be dropping from the trees to enter their adult stages. "The damage is done," Mucklow said.
The males will become small brown moths, and the females will become wingless adults. And although the females will climb back up the trees in the late summer or fall to lay eggs, there is little chance of a similar outbreak next year, according to Whitney Cranshaw, extension entomologist for Colorado State University.
"It would be next year - if we have this outbreak again - (that) we would recommend checking early and treating so the trees don't defoliate two years in a row," Mucklow said.
Mucklow said caterpillar damage throughout the course of two years is when there is a real risk of losing trees.
If people decide to treat the caterpillars this year - because they are a particular annoyance or targeting a valued tree, among other reasons - Mucklow said they are easy to kill and recommends the natural insecticide Bacillus thuringiensis, also known as Bt.
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