OLYMPIA - The gypsy moth trapping program operated each summer by the state Department of Agriculture is under way.
Some 900 cardboard traps will be placed in Thurston County and 22,000 will go up statewide in search of an invasive pest that attacks more than 500 species of trees and plants.
This state has never had a permanent population of gypsy moths, but 19 states in the East and Midwest are not so fortunate. Thousands of acres have been infested in those states.
In its caterpillar stage, the pest quickly strips trees and plants of leaves, destroying some and weakening others so they are susceptible to plant diseases. The pest can also trigger costly quarantines of timber, crops and nursery products.
The state launched its summer trapping strategy in 1974 and will spend about $750,000 this year on the program, said agriculture department spokesman John Lundberg.
The traps are inspected every two or three weeks through September. When moths are found in significant numbers, the state follows up with an eradication program in the spring when the moths are in a caterpillar stage, using a naturally occurring microbal “insecticide” called Bacillus thuringiensis (Bt).
The last time Bt was used was 2007 in Kent. The last moth infestations requiring treatment in South Sound were in the Hunter Point and Black Lake areas in 1996.
The number of gypsy moths caught annually in the varies from 17 in 2002 to 1,315 in 1983. Last year, 18 moths were caught, including one in Olympia.
Areas in Thurston County slated for the heaviest concentration of traps due to past gypsy moth activity include:
• Near the intersection of Lilly and Stoll roads in Olympia.
• East of Olympia near the intersection of Old Highway 99 and 79th Avenue Southeast.
In addition, the Port of Olympia will have a larger number of traps because of the threat of Asian gypsy moths coming off foreign ships at the port.