MADISON, Wis. (AP) - Activists opposed to the growth of big industrial farms in Wisconsin have asked a towns association to develop a model ordinance that communities can use to limit aerial manure spraying.

Members of the Sustain Rural Wisconsin Network say the practice creates health risks because bacterial and other pathogens found in untreated manure could get into the air, particularly when there are strong winds.

"These sprayers are being promoted as innovative technology," said Bob Clarke, president of SRWN, "when in fact they have the potential to expose the people to disease outbreaks, severe diarrhea, and growing antibiotic resistance."

But Department of Natural Resources Secretary Cathy Stepp and Agriculture Secretary Ben Brancel asked the Wisconsin Towns Association and Wisconsin Counties Association to hold off on taking action until there's a proven health risk.

"As leaders of your respective associations, we encourage you to work with your members to make sure they do not adopt local ordinances that restrict the use of approved and accepted technologies unless it can be documented and demonstrated that there are environmental or public health risks associated with them," Stepp and Brancel wrote.

Wisconsin Towns Association Executive Director Richard Stadelman said there are many misconceptions about the systems.

"Some people think we're shooting cow pies way up in the air," he said. "We're not."

Andrew Craig, a nutrient management specialist with the Department of Natural Resources, said there are two types of aerial spraying systems. One is similar to an irrigation system with a center pivot and nozzles that face down. The second is like a big sprinkler.

Many farms now haul manure in to spread on farms, but Craig said the aerial systems, which transport liquid manure through pipelines, are less expensive and more precise in how they apply manure. He estimated six farms have the equipment now and one or two use it regularly.

"It's not very common," Craig said, "but it's going to become more common."

The Wisconsin State Journal ( reported that some towns, including Rosendale, which has the state's largest dairy operation, have already banned the systems.

Mike Dummer, who raises grain and hogs near La Crosse, said he has used a manure irrigation system for 25 years with few complaints.

"We work hard to be good neighbors," he said. "A lot of it is just common sense. A lot of times we spread at night when the wind is down and people have their windows closed."

He too said the system has advantages in eliminating the use of trucks and allowing him to be more precise in applying manure.

"We're spoon-feeding the crops," Dummer said.

The federal Environmental Protection Agency has identified 160 pathogens in manure that can cause disease in people, and one of SWRN's chief concerns is that they will be picked up by wind and spread during aerial spraying.

Craig said there are already regulations barring the use of aerial spraying closer than 500 feet to a home and within certain distances of wells and groundwater supplies.