Maine farmers are divided over a legislative proposal to change a new system for notifying residents of pesticide spraying near their homes.

The pesticide notification law, passed unanimously last year in the Senate and the House, created a statewide registry so residents who live within a quarter-mile of any farm or other spraying site can sign up to be notified before spraying is done.

More than 550 people have signed up since the registry went online in September. At the same time, opposition to the measure has mounted among commercial growers and sprayers.

“It appeared to fly under the radar somewhat” in the Legislature last year, said Henry Jennings, director of the Maine Board of Pesticides Control, which is responsible for overseeing the new registry.

A pending floor vote on a bill to water down the law has triggered a last-minute campaign by the Maine Organic Farmers and Gardeners Association and other groups to save the new notification system. Commercial growers are supporting revisions to the law, which they say is unnecessary and burdensome.

“We are frustrated that this has been about conventional growers versus organic farmers when it is a public health issue,” said Heather Spalding, associate director of the organic farming association, which came up with the initial legislation.

Part of the controversy surrounds a provision in the law that requires farmers and commercial sprayers, such as mosquito control companies, to notify neighbors 90 days in advance of plans to apply pesticides by aircraft or equipment on the ground.

Farmers say they often don’t know three months in advance which of their fields they will plant. Mosquito control companies said they don’t know who their customers are 90 days in advance, so they can’t notify people in the registry.

Even supporters of the registry agreed that the law would be cumbersome and worked to come up with changes, through a bill sponsored by Rep. Andrew O’Brien, D-Lincolnville.

During a six-hour hearing and four work sessions on the issue, the Legislature’s Agriculture, Conservation and Forestry Committee came up with a proposal that went beyond O’Brien’s.

The panel’s changes would reduce the notification distance for residents from a quarter-mile to 500 feet for orchards and Christmas tree growers. Spraying for non-agricultural purposes — such as forestry, rights of way and mosquito control — would be exempt from notification until 2012.

Some apple growers say they welcome the proposed changes because the law would have created unfounded alarm about pesticide drift.

Ellen McAdam, whose family operates McDougal Orchards in Sanford, said no one in town has signed on to the registry, and there were already laws to protect people from aerial pesticide drift.

“It would be hard to produce a commercial crop without some sort of pest control,” she said.

McAdam, past president of the Maine Pomological Society, said many people who have signed up for notification — Kittery and Gorham residents are heavily represented on the registry — don’t live near significant agricultural areas.

But opponents to the changes say they hope the Legislature will back away from major revisions. The American Lung Association is lobbying against weakening the measure, calling pesticide spraying a serious health threat for the 10 percent of Mainers who have asthma.

“This is an issue that has been debated in the agriculture community as opposed to the public health community, and that is one of the things we are concerned about,” said Ed Miller, vice president of public policy for the lung association.

The Legislature is expected to vote on the matter by the end of this week.

Staff Writer Beth Quimby can be contacted at 791-6363 or at: bquimby@pressherald.com