Special scent meant to disrupt gypsy moth

Pheromone “flakes” will be released over Decorah June 27 to disrupt the mating of the destructive gypsy moth.

State Epidemiologist Robin Pruisner and Iowa Department of Natural Resources Forest Health Specialist Tivon Freeley presented information to the Decorah City Council recently on the planned mating disruption treatment.

A Boston, Mass., professor introduced the gypsy moth to the Unites States from Europe in 1869 as an experiment to improve the silk industry. A windstorm knocked over cages, and the insect was accidently released into the forests of Massachusetts, according to Iowa State University Extension. Since that time, the moth has been spreading west and south.

There has been monitoring of gypsy moths since 1970 in Iowa. Recently, moth traps have been concentrated in the northeast part of the state, since an infestation is moving in from Wisconsin and Illinois, Pruisner said.

“Our focus is to slow the spread and keep our forest woodlands and yards from experiencing massive defoliation, that, when occurring in back-to-back years, kills many of the trees,” Pruisner said.

Gypsy moths eat over 500 species of trees and shrubs and especially like to feed on oak trees.

The Iowa Department of Agriculture and Land Stewardship and Iowa Department of Natural Resources, in cooperation with the USDA Forest Services and Iowa State University (ISU) have been working together to plan a total of four gypsy moth mating disruption treatments this year in Iowa. In addition to the one planned for the Decorah area, aerial applications will take place in Allamakee and Jackson counties this spring.

Not a pesticide

The pheromone flakes are the same thing that is used in gypsy moth traps. They are the size of “chopped oatmeal, but blue,” Pruisner explained. About six ounces per acre is applied.

Mating disruption is not a pesticide application but a low dose of the pheromone scent that a female releases to attract a male.

The treatment prevents the male moths from finding females, stopping mating activities, she said.

“The pheromone affects no other species of insect nor animal, nor does it have any impact on humans,” Prusiner said.

The practice has been used for decades to slow the destructive spread of gypsy moths in eastern states.

“When the males can't find the females, the populations crash,” Pruisner said.

About 22,886 acres within an 89,104-acre area in Winneshiek and Allamakee County will be treated, she said. The nonprofit Slow the Spread organization will pay for the treatments. Once an area is considered infested, cities and counties have to pay 50 percent of the treatment cost and the Forest Service pays for the other 50 percent.

“The exact areas to be treated are determined by a computer algorithm that looks at trap catches, proximity to other positive traps and proximity to the infested areas just east of Iowa,” she said.

Natural predators

Council member Steve Matter asked why birds don't get rid of the gypsy moths.

Because it's an exotic pest, it doesn't have a lot of natural predators, Feeley said.

The white-footed mouse is currently the only known predator, Pruisner said. Over time, she said more natural enemies would emerge.

Mayor Don Arendt asked what would happen without mating disruption treatment, and Pruisner said the Decorah area would become infested in a few years. When gypsy moths become more prevalent, other treatments, that must be used with care around waterways, are the only options for dealing with the pests. Using pheromones is the “least noxious” method, she said.

Pruisner said local residents returning from nearby states with infestations of gypsy moths should check all their gear for “hitchhikers.”

Gypsy moths can be moved long distances when people unknowingly carry them from infested areas as egg masses or cocoons attached to firewood, campers, nursery stock, outdoor furniture or vehicles, she explained.

When asked if she'd heard any objections to pheremone treatment for gypsy moths, Pruisner said once people hear her presentation and have their questions answered, they have none. Freeley said he's even had someone offer to pay for the treatment if funds weren't available for it.