John Miller, Associated Press
A field of flowering Ranger russet potato plants is pictured near Wilder, Idaho, on Wednesday, June 12, 2013. A team of scientists at the University of Idaho is trying to find a way to stop a microscopic parasite that damages potato crops and has now infested 2,400 acres in southeastern Idaho.

BOISE, Idaho — A team of scientists at the University of Idaho is trying to find a way to stop a microscopic parasite that damages potato crops and has now infested 2,400 acres in southeastern Idaho.

The U.S. Department of Agriculture announced that the eight-year-old infestation of the pale cyst nematode is up to 22 fields within a 5-mile radius. The fields are in northern Bingham County and southern Bonneville County. The agency in a release Wednesday says 8,500 acres in all are being regulated.

Meanwhile, university researchers are trying to find ways to eradicate the nematode with methods besides harsh chemicals that are being phased out because of concerns about human health and the environment.

"The nematode is confined to a small area in southeastern Idaho, and it's not very mobile," said Dr. Louise-Marie Dandurand, director of the Pale Cyst Nematode Project at the University of Idaho. "So with that in mind, I think we do have a good chance of achieving the goal we have."

The discovery of the pale cyst nematode in seven fields in 2006 was the first detection of the pest in the U.S. Authorities have been trying to eradicate it ever since with some success. In May, though, authorities announced the discovery of the nematode in a 92-acre field in Bingham County.

The team at the university includes experts in molecular plant pathology, biochemistry and weed science, all searching for a solution.

"It's extremely difficult," said Allan Caplan, an associate professor and an expert on plant molecular biology and genetics. "It's especially difficult because the chemicals we've been using are pretty toxic and they're being phased out. It doesn't pay to save the food but kill the person who eats it."

It not clear how the pest arrived in Idaho. After its discovery, some countries initially closed their markets to Idaho potatoes before reopening them. Japan, though, still refuses to import Idaho potatoes.

The nematode presents unique challenges, especially when it's in the egg form.

"It's hard for chemicals to even penetrate those shells," Caplan said. "So you have to wait for them to emerge and then kill them. The eggs are able to stay in the soil in some cases for years."

Also, scientists said, the chemicals currently being used tend to kill everything in the soil, including organisms that are beneficial to have in the soil.

So researchers have been working on an array of other methods. Those include tricking the nematode eggs into hatching when there's no food available, creating sterile forms of weeds that kill the nematodes, using a nematode eating fungi, and even creating a genetically modified potato that can itself fight off the nematode.

However, Caplan said, the social resistance to genetically modified food could preclude that method.

In the end, the scientists said, a combination of methods will likely be needed to stop the pale cyst nematode.

"This is one of the most important pests of potatoes worldwide," Dandurand said. "In potato growing regions, this will be the No. 1 problem of potatoes. So I think it's worth the effort."