Caterpillar outbreak surprises Hayden resident


Take a walk around Frank Welsh's property 10 miles south of Hayden and it won't take long to see the scale of the caterpillar infestation there.

If caterpillars sticking to your clothes or falling down the back of your shirt don't convince you, a glance into almost any of the trees on Welsh's 50 acres will reveal hundreds -- if not thousands -- of the leaf-eating insects. Give a tree a shake and the caterpillars will fall to the ground by the dozen.


Welsh first noticed the problem early last week during a horseback ride around the property with his girlfriend. The two were puzzled as they found themselves being covered by caterpillars. But the real annoyance came when Welsh saw what the caterpillars were doing to his trees -- devouring their leaves, and fast.

"I've never seen anything like this at all, and we've been here for eight years," Welsh said. "I'm really upset about it. I just want to see something done about it."

While walking on his property Wednesday morning, Welsh laments the lack of vegetation on his trees -- the caterpillars are targeting his aspen, scrub oak, sarvis and chokecherry trees -- and describes how lush they usually are this time of year. Welsh said he wanted to spray the caterpillars immediately, but an adjacent property owner wanted time to learn more about them. The neighbor, Doug Kiesau, took some of the caterpillars to the Colorado State University Cooperative Extension Service Office in Steamboat Springs.

"I don't know what they are," said C.J. Mucklow, the county's extension director. "They're not in any of my books, which is weird."

Mucklow sent the caterpillars to a diagnostic lab at Colorado State University and hopes to hear back from lab scientists before the end of the week. He said the Extension Office has received several calls about the insects and that the caterpillars appear to be spread from South Routt to west of Craig.

Mucklow won't know much about the caterpillars, how their outbreak came about or what to do about them until he hears back from the diagnostic lab. He is "pretty sure" it is a native outbreak, which is not necessarily uncommon for Routt County. Mucklow said the last similar outbreak was of tent caterpillars about a decade ago. Mucklow said the outbreak was mostly likely the result of a perfect storm of conditions that led to a population explosion.

Fearing the caterpillars will soon enter their larvae stage and lay eggs, Welsh still hopes to kill them by spraying as soon as possible. He plans to have the insecticide carbaryl, also known by its trade name Sevin, sprayed by airplane as soon as the weather permits. According to the Environmental Protection Agency, carbaryl is one of the most widely used broad-spectrum insecticides in agriculture and residential pet, lawn and garden markets. Among its ecological risks, carbaryl can be especially harmful to honeybee populations.

"No insecticide separates good insects from bad ones," Mucklow said. However, spraying early or late in the day, as Welsh plans to do, can mitigate the risk to beneficial insects, and Mucklow said carbaryl is a viable option for those looking to eradicate the caterpillars.

Welsh is a plumbing contractor, so the caterpillars don't pose any sort of financial setback. And while the caterpillars are proving an annoyance to many, Mucklow said there shouldn't be any economic consequences.

"It's not an agronomic problem," Mucklow said. "It's a horticultural and aesthetic problem."

In the past, Mucklow said caterpillars have never killed a healthy tree in the county, although any tree that is weakened runs that risk. He said the county might see some bad growth for a time as a result of the caterpillars, but "this is not the end of trees in Routt County."

Commenting has been disabled for this item.