WENATCHEE – Outbreaks of Douglas fir tussock moths are expected this summer in the Methow Valley, Lake Wenatchee and Blewett Pass areas.
Surveys of tussock moth egg masses have been monitored for months by teams from the U.S. Forest Service and state Department of Natural Resources.
Although periodic outbreaks are a natural part of the ecosystem of the Cascades, forest staff plan to use a natural bio-control in high-use recreation areas to minimize public safety issues, said the Okanogan-Wenatchee National Forest.
“Public safety is always our top priority,” said Forest Service Entomologist Connie Mehmel. “The natural bio control we’ll use has no chemical insecticide whatsoever. Our goal is to spray caterpillars before they grow big enough to cause damage in high-use areas.”
This year the project will involve aerial application of a naturally occurring virus, toxic only to the tussock moth, called TM Biocontrol-1, on up to 8,000 acres of public lands north, both sides of Blewett Pass in Kittitas and Chelan counties, and the Lake Wenatchee area.
The virus would be applied using helicopters as early as the second week in June and as late as the last week in June, depending upon when insects hatch and caterpillars are most vulnerable to the virus.
“The biocontrol is sticky - it’s a mixture of water, molasses and the virus,” said Mehmel. “Visitors will want to avoid areas on days when spraying occurs, as you probably wouldn’t want to get this sticky substance on your clothing or your vehicle.”
Forest visitors should also be aware that hairs from tussock moth caterpillars can cause allergic reactions for some people and their pets in an outbreak area.
Long-term, forest managers will continue to use restoration tools, such as thinning and prescribed fire, to increase forest health and resilience to disease and insect outbreaks such as tussock moth, said forest officials.
The last severe outbreak in Washington occurred from 1999 to 2002, with more than 45,000 acres defoliated.