FOR IMMEDIATE RELEASE
July 28, 2011
DNR observes tree-damaging caterpillar in Spokane County
Landowners and recreationists asked to look for signs
OLYMPIA – The Washington State Department of Natural Resources (DNR) announced today that new forest defoliation (loss of leaves) by the Douglas-fir tussock moth is becoming apparent in Spokane County. Affected areas include Mica Peak, Tekoa Mountain, Gelbert Mountain, and adjacent forests across the border into Idaho.
Landowners and recreationists should avoid handling tussock moth caterpillars because their hairs are a skin irritant to many people.
Caterpillars are actively feeding and growing larger, leaving behind red-colored damaged foliage. Defoliation damage tends to be worse in the tops of trees and appear pale or reddish as damaged needles dry out.
Landowners who want to reduce damage from Douglas-fir tussock moth should consider careful tree thinning to change stand conditions to be less vulnerable to defoliator damage. This strategy commonly includes protecting the pine and larch, which are not eaten by these caterpillars, while removing more Douglas-fir and grand fir, which are eaten. Insecticides can be applied to reduce tree damage, but are less effective when caterpillars have matured into pupae and stop eating, usually by mid-August.
In 2010 aerial surveys, DNR and the U.S. Forest Service detected approximately 570 acres affected by Douglas-fir tussock moth in Spokane County. Ground surveys indicated that defoliation in these areas would expand and increase in severity in July and August of 2011. The defoliated areas have not yet been surveyed from the air in 2011.
The Douglas-fir tussock moth is a native insect. Tussock moth outbreaks are cyclical, causing damage somewhere in Washington approximately every seven to ten years. The last outbreak in Washington occurred in Okanogan County from 2008 to 2010, leaving more than 3,500 acres defoliated at its peak in 2009. The last outbreak in the northern Idaho-Washington State border area was from 2000-2002.
Tussock moth caterpillars start by feeding on new foliage but later eat older needles, and they can cause significant damage in a single season. The tussock moth primarily affects grand fir and Douglas-fir. This damage can reduce growth, cause top-kill, and may predispose some trees to attack by bark beetles. Tussock moth outbreaks typically collapse within two to four years due to a buildup of natural enemies, such as a virus and parasitic flies. Most likely, 2011 is the third year of this outbreak.
To evaluate management options, DNR can assist forest and woodlot property owners in the affected area who observe Douglas-fir tussock moth and tree damage. Detailed information on how to recognize Douglas-fir tussock moth damage, maps, and images are available on the DNR website: http://www.dnr.wa.gov/ResearchScience/Topics/ForestHealthEcology/Pages/rp_foresthealth.aspx
To report tussock moth damage or for more information, please contact Glenn Kohler, Washington DNR Forest Entomologist, at 360-902-1342 or email firstname.lastname@example.org .
Janet Pearce, Community Outreach and Education, 360-902-1122, email@example.com
Glenn Kohler, Forest Entomologist, 360-902-1342, firstname.lastname@example.org
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