The Minnesota Department of Agriculture plans to begin aerial spraying to treat the state's largest infestation of gypsy moths to date. The imported moth is the nation's most destructive pest of trees and shrubs. It has not yet established itself in Minnesota, but has worked its way eastward as far as Illinois.

	Gypsy moth caterpillars can defoliate trees at an alarming rate, according to officials. (Photo courtesy of USDA Forest Service)

The exact time of the spraying will depend on wind and weather conditions, but the agriculture department says it could be as soon as next week.

Helicopters releasing a mist of the natural insecticide BTk are expected to fly over neighborhoods in south Minneapolis, Golden Valley, and a small part of St. Louis Park.

The department's Kimberly Thielen-Cremers says BTK is a naturally occuring bacterium. It is certified for use by organic growers. It's toxic only to caterpillars in early stages of growth. She says it's caused no documented harm to humans, pets, animals, or birds, but it may be an inconvenience.

"It's a very small droplet size, so its a very fine mist. We ask folks just to stay indoors, if they don't want to be out during the treatment. We give about about a 30-minute time frame, that just gives it enough time to dissipate in the air. Not that we feel there's any harmful effects to humans, it's just that it's unpleasant to be sprayed. Any pets that they have out, again, if they feel that the helicopter will spook them, to have them indoors," Thielen-Cremers said.

The department has been fighting small outbreaks of gypsy moths in Minnesota since 1980. Over the years, it has treated more than 1,600 acres, including a number of residential areas. But this latest treatment will be by far the largest to date in Minnesota. It will be nearly 3,000 acres - almost twice the total area treated to date.

	Helicopter pilot Mike Balch estimates it will take several hours to spray the neighborhood south of Lake Harriet. He says he flew a similar spraying program in a Chicago suburb in 2000 and the operation went well, although reaction at first was mixed. (MPR Photo/ Mary Losure)

So far, neighborhood residents seem to have expressed few concerns. Rep. Jean Wagenius, DFL-Minneapolis, represents the Minneapolis neighborhood south of Lake Harriet where the first spraying will take place this spring. Wagenius sits on two environment committees and often acts as a watchdog on pesticide issues. She says she's heard very little from her constituents . She says she is satisfied that the pesticide is safe.

"My first question to the Department of Agriculture was what kind of tests has this spray been through? What would be any possible effects on children? They did some research on that question, nobody has asked them that question before. I also did some independent research on my own, and it seems that this particular spray is probably just fine," Wagenius said.

Still, the agriculture department is handling the issue carefully. It has sent letters to all the affected residents, set up a hotline, and posted information on its website.

On Monday, department officials invited members of the press to photograph the helicopter that will do the spraying. The helicopter's pilot, Mike Balch, described the planned operation, which will based at the Flying Cloud Airport in Eden Prairie.

"It will be first light in the morning, we'll probably leave out of here at dark, 4:30 to 4:45, and there's a little park area they're setting up to use as a heliport on the south side of the Lake Harriet site. That's where the staging area will be. We have a truck that will hold the chemical, and we actually land on top of the truck, and it has fuel and chemical and water, and we'll pump on to the helicopter from there, and just take off like normal from that truck and head for the spray site and begin spraying operations if weather conditions are conducive to spraying," he said.

Balch estimates it will take several hours to spray the neighborhood south of Lake Harriet. He says he flew a similar spraying program in a Chicago suburb in 2000 and the operation went well, although reaction at first was mixed.

Officials from the US Forest Service and the Federal Department of Agriculture say spraying outbreaks of gypsy moths could postpone the establishment of the pest in Minnesota for as much as 15 years, and delay much of the damage and economic costs.

Late last month, State Attorney General Mike Hatch ordered the department to suspend its gypsy moth program because it will expose humans to aerial pesticide spray. The state Legislature is now working to amend the law to allow gypsy moth treatment.

Agriculture department officials say they expect the bill will be passed and signed in time for the spraying to begin on schedule.