Return of the gypsy moth?

The Oregon Dept. of Agriculture’s insect management traps, like this one hanging from a tree branch at the Leaburg Boat Landing this summer, have been closely monitored.

The Oregon Dept. of Agriculture reports it has been another relatively quiet year for gypsy moth detections, but the discovery of two moths in a single trap near Grants Pass has caught their attention.

While the discovery is a far cry from the mid-1980s when more than 19,000 of the plant-eating pests were trapped in Lane County alone, it’s a reminder that gypsy moth remains a threat to Oregon’s agriculture and forest habitat.

“We can’t let our guard down because we know the gypsy moth will come back,” says Helmuth Rogg, manager of ODA’s Insect Pest Prevention and Management Program.

Due to budget constraints, ODA placed only 8,000 gypsy moth traps statewide– about half as many as desired. All traps will be picked up by the middle of October, so it’s possible additional gypsy moths will be found. But to date, there have been only the two Grants Pass detections. Last year, only one gypsy moth was trapped, in Eugene. In 2011, there were no detections. The pattern suggests the threat is low, but Rogg and other entomologists are not convinced.

“Next spring will be the fifth year in a row that we have not had a gypsy moth eradication project somewhere in the state,” he says. “But it’s not a question of if it will happen again, but when.”

New introductions have routinely taken place in past years. New residents or travelers from areas where gypsy moth populations are heavy unwittingly bring the insect pest with them on such things as outdoor household furniture or other items that may harbor gypsy moth eggs. It only takes one female gypsy moth to lay eggs in Oregon and start up a new population of the invasive species. That’s why the trapping program is so important, even in years when the detections are few. Finding gypsy moths as soon as possible and quickly eliminating breeding populations allows ODA to successfully prevent economic and environmental losses to Oregon, either through restrictive quarantines on commodities or by the loss of foliage and even trees due to expanding gypsy moth populations.

Even though Oregon has enjoyed a respite from gypsy moth infestations, there are a couple of reasons to expect a change.

“Gypsy moth populations back east go through cycles and the insect pest will soon be coming out of a downswing,” says Rogg. “We’ve also benefitted the past five years from the economic recession, which has reduced people traveling and relocating to Oregon from infested areas back east.”

It is very likely that the introduction of gypsy moth to a residential area northwest of Grants Pass this year stems from a move-in or visitor from another state where gypsy moth is common. ODA will be sending out notices to residents in the neighborhood hoping to learn if anyone has moved to the area from such a location in the past three years. If the source can be found, survey technicians will attempt to look for gypsy moth egg masses or other evidence that pinpoints the spot of a potential breeding population. It’s a long shot, but such a discovery would help confine the area for placing additional traps next year.

“It’s like looking for the famous needle in the haystack,” says Rogg. “So we aren’t counting on finding egg masses. But the plan for next year is to put many more traps in the neighborhood to find out if the population of gypsy moths is indeed reproducing and how far out it has already spread.”

Perhaps more concerning than the detections in Josephine County was this summer’s discovery of Asian gypsy moth egg masses aboard ships navigating the Columbia River from Russian ports. ODA has worked with US Customs and Border Protection (CBP) as well as USDA’s Animal Plant Health Inspection Service (APHIS) to inspect vessels arriving in Oregon that may be transporting hitchhiking invasive pests from infested areas overseas. Two Russian cargo ships were found to be carrying egg masses of the Asian gypsy moth.

This version of the insect is potentially more serious, therefore requiring immediate attention even if only one moth is trapped. Unlike the more common European gypsy moth, female Asian gypsy moths are strong fliers and are attracted to lights, allowing populations to spread much more rapidly. In addition, the Asian gypsy moth feeds on a broader range of host trees, including conifers. Areas of the Columbia River are at greater risk for the introduction of Asian gypsy moths due to cargo ships arriving from infested areas in Asia. ODA always makes sure to place traps along areas of port activity, including the Columbia. In the 90s, ODA had treated for Asian gypsy moth in North Portland and Portland’s Forest Park– both located next to the river and port areas.

“The risk of gypsy moth establishing in Oregon is constant,” says Rogg. “If not from the eastern part of the US, the threat is from Asian ports where cargo and commodities come to Oregon infested with gypsy moth egg masses. We know the pathways for gypsy moth and we are focusing on those pathways to place traps.

Again, we want to catch as early as possible any population of gypsy moth that is starting to establish so we can reduce the area that needs to be treated.”

With fewer gypsy moth traps being placed around the state earlier this year, a higher concentration were located in areas known to be at greater risk of introductions– mostly on the west side of the Cascades and in areas more easily accessible to survey technicians. But ODA received an assist this year from the Oregon Department of Forestry and US Forest Service, which placed traps in some of the more heavily forested and remote areas of the state. In fact, it was a trap placed by ODF that actually caught the two gypsy moths found in the Grants Pass area.

Not since 2009 has a gypsy moth eradication project been needed– the longest stretch of no gypsy moth spraying since the huge Lane County infestations of the mid-1980s, when more than 225,000 acres were treated. Oregon still has a chance to keep the nasty insect pest from becoming a permanent resident. The goal is to not have to learn to live with the pest the way residents do on the East Coast. ODA’s robust trapping program, so far, has helped Oregon keep its gypsy moth-free status.