Colorado State Forest Service Setting Traps for Invasive Moth Statewide

Wondering about that green, tent-shaped contraption that recently appeared on a traffic sign in the neighborhood?

“It’s a gypsy moth trap,” said Sky Stephens, forest entomologist for the Colorado State Forest Service. In an effort to capture and monitor the presence of this invasive species, four seasonal technicians under Stephens’ guidance are placing more than 1,700 of the football-sized traps in virtually every large town in Colorado. Technicians began setting traps in late June and will continue through the end of July; the traps will remain set until the fall.

The gypsy moth, which is capable of extensively defoliating most deciduous tree species, has been detected almost yearly in Colorado since 1989. The CSFS is working with the USDA Animal and Plant Health Inspection Service and the Colorado Department of Agriculture to prevent the Eurasian insect from establishing itself here, but it is too late to prevent its establishment elsewhere in the nation. States in New England and the Midwest already have significant gypsy moth populations and large campaigns to help mitigate damage from the moths.

“This program is vital to prevent the tremendous potential impact an invasive species like the gypsy moth could have on Colorado trees and forests,” Stephens said.

The traps have a sticky interior similar to flypaper that captures male moths lured in by artificial female pheromones; only male moths can be trapped, because the larger female gypsy moths do not actually fly. If moths are captured, a team of CSFS, CDA and APHIS technicians traps the surrounding area more intensively the following year and conducts a thorough search for the presence of moth populations.

The CSFS sets traps each year in public right-of way-areas, which is why the green objects often can be seen on stop signs and telephone poles instead of trees growing in private yards. More traps are set in densely populated communities and campgrounds, because vehicles coming in from other states allow the moths to hitch a ride into Colorado. In 2009, the project netted three male moths – in Westminster, Commerce City and Pueblo; each capture location was near an area frequented by recreational vehicles, which are known to be a major contributor to the accidental spread of gypsy moths.

Stephens asks that anyone coming across the traps refrain from removing or damaging them. “Lots of traps disappear each year, which compromises our ability to detect the presence of this damaging insect,” she said. “We ask that people leave the traps in place, and call the phone number listed on the trap if they have concerns.”

CSFS technicians also are currently setting larger purple traps for the emerald ash borer, another invasive insect the agency is monitoring in Colorado.

For more information, contact Stephens at (970) 491-7282 or