Crews hunt gypsy moths

A single Asian gypsy moth found last month near Hauser, Idaho, has prompted an intense effort to prevent the voracious forest pest from becoming established in the Inland Northwest.

With their ability for flight and their hunger for both deciduous leaves and evergreen needles, Asian gypsy moths are considered a much greater threat than their North American cousins, which have devoured Eastern hardwood forests. Until now, none of the Asian moths had been found in Idaho or Washington east of the Cascades.

Crews from the Idaho Department of Lands continue to search for egg masses, shed larval skins or empty cocoon cases, but no further evidence of the moth has been found, said Ladd Livingston, a forest entomologist with the Idaho Department of Lands. If caught early, the outlook is good for a successful eradication, Livingston said. Still, officials are treating the discovery with the same care taken by a bomb squad.

“This find represents a very real threat to the health of Idaho’s forests and must be dealt with swiftly to assure the moth doesn’t become established,” Livingston said.

Gypsy moths from Europe have been munching hardwood tree leaves since they were accidentally released from a Massachusetts home in 1869. A naturalist had been trying to crossbreed the species to launch a domestic silk industry. The moths now chew away about $30 million each year, but do not attack conifers, according to the U.S. Department of Agriculture.

Minor outbreaks of North American gypsy moths have occurred in Idaho and Washington, but intense monitoring has kept the moths from becoming established, said Ed Bechinski, entomology professor with the University of Idaho. The North American moth is too heavy to fly, which has prevented a large-scale invasion. Many gypsy moths are believed to arrive in the West as eggs attached to travelers’ vehicles.

“We have the advantage of being separated from the Midwest by the Great Plains,” Bechinski said. “The moth can’t feed its way across the country.”

Washington sets out 21,000 pheromone-baited moth traps each year. This season, 68 North American gypsy moths were trapped; none in Eastern Washington, said John Lundberg, with the Washington Department of Agriculture’s Pest Program.

Idaho places about 5,600 of the cardboard traps each year. Apart from the single Asian moth, there have been no other gypsy moths captured in the state this season, according to preliminary results from the state’s Land Department. North American gypsy moths were last found in Idaho in 2001.

Asian gypsy moths arrived in the United States in 1991 – the Iron Curtain had recently fallen and the moths arrived in Tacoma on a load of logs from the infested Russian port of Vladivostok, Lundberg said. The Asian moths have been trapped in the state eight times since. All of the occurrences have been in the Seattle area and control efforts are believed to have been successful, Lundberg said. No Asian moths have been spotted in Washington since 1999.

With the discovery of the Asian moth, Washington plans to step up its trapping program next year along the Idaho border between Spokane and Coeur d’Alene, Lundberg said. The Asian moth’s ability to fly makes early detection critical – an egg mass from a single female can unleash 1,000 hungry caterpillars in the spring and a major outbreak the following year.

“For a state that’s very dependent on timber, you bet we’re concerned,” Lundberg said. “We’re very concerned.”

Although the moths are well-camouflaged, scientists have developed effective control and tracking mechanisms, Lundberg said. In 2003, for example, a minor North American gypsy moth outbreak in Western Washington was traced to a single birdhouse brought to the state by transplants from Pennsylvania. The area was subsequently sprayed.

“We didn’t catch a single moth there this summer,” Lundberg said.

The Asian moth found last month was trapped near Curley’s Dining Car Lounge in Hauser. Livingston, with the Idaho Department of Lands, suspects the moth began its journey as an egg on a rail shipping container from Asia. Much of the freight from Washington’s ports passes through a railroad refueling facility near Hauser. When the caterpillar hatched and found no leaves or needles to eat, it shot out a strand of silk and was picked up by the breeze.

“It came across the Pacific, probably on some kind of freight container. It probably blew off the railroad car, but that’s not proven,” Livingston said.

A bacterial-based control spray is being considered for use in the Hauser area during spring, Livingston said. The spray uses the Bacillus thuringiensis bacteria, which is commonly found in soils and disrupts the feeding ability of the Asian gypsy moth. The spray is often used by organic farmers for treating other agricultural pests.

Scientists with the U.S. Department of Agriculture visited Hauser last week to discuss control strategies, Livingston said. “We hope this is an isolated find.”