IDAHO FALLS, Idaho — Potato ring rot — a spud disease so serious that it’s sometimes called the “AIDS of potatoes” — has hit Idaho’s seed potato capital in full fury.

Twenty-one growers, mostly in the Ashton area, have lost their seed potato certification because of the bacteria.

Ring rot can cause complete decay of the tuber and mean huge losses for the seed potato industry. This year could be especially tough for those growing seed to sell on the open market, since the spud market already is glutted by a big crop.

Ring rot is an extremely sensitive issue, since the disease can cause seed potato fields to lose their disease-free reputation. Several eastern Idaho growers refused to comment on the problem.

Eastern Idaho fields were dotted with ring rot last year, but the incidence of the bacteria has quadrupled in this year’s seed potato crop, according to figures just released by the Idaho Crop Improvement Association.

“I’ve just never seen it like this before,” said Bart Roberts, a Newdale grower whose fields were hit with ring rot for the first time this year.

While Roberts’ farm had no ring rot last year, he said the disease was more prevalent on others’ farms than he’s ever seen before.

According to ICIA figures, 1,790 acres in the eastern Idaho area lost seed certification because of ring rot in 1990. This year, it’s 6,899 acres losing seed certification.

Certification is important to growers because it’s an assurance that the seed potatoes will be disease-free.

Ring rot is difficult to control because seed spuds are cut in pieces for planting. Ring rot bacteria can remain on farm equipment or cutting blades and spread to other seed potatoes, said Phil Nolte, a seed potato specialist for Bonneville County.

“It’s just a devastating disease,” Nolte said.

Ring rot is so serious and contagious that a grower who has a single infected plant will lose certification for the entire field. Infected spuds often show no symptoms until they have spread the bacteria to other potatoes.

Most of the infected fields this year are in Fremont County, eastern Idaho’s seed potato capital with more than 12,000 acres certified to sell spuds for seed. This year 2,453 acres lost their certification, up from 535 acres last year. Other hard-hit areas include Bonneville, Jefferson and Teton counties.

R.K. Egbert lost certification on 1,100 acres because of the rot.

“It’s a really bad situation,” he said. “This is really going to hurt.”

Egbert called his buyers and informed them of the problem, and canceled some deals. While that hurts him this year, it may also hurt him and other area seed potato growers in the years to come. Buyers might fear the disease will recur or show up on certified fields.

Many growers, such as Brad Rhodes of Ashton, plan to sell their potatoes on the open market. But processing and fresh-pack spuds are netting low prices right now because of increased supply.

“If it weren’t a good spud year, this wouldn’t affect us so bad,” Rhodes said.