Ray and Bryan Searle of Double S Farms near Shelley, Idaho. (Courtesy Double S Farms)

SHELLEY, Idaho — A potato field’s recent release from government regulation marks a milestone in the nearly two-decade battle against the Pale Cyst Nematode, farmer Bryan Searle said.

“This is the first field that has been released from this tight regulation in 19 years,” he said. “We are hopeful we can repeat that with some opportunities going forward.”

Pale Cyst Nematode was found in Idaho in 2006, prompting a major eradication effort. A serious invasive pest in potatoes, the nematode can cause up to 80% yield loss and can survive in soil for long periods, according to the University of Idaho.

Eradication efforts include quarantines and fumigation.

Searle and his son, Ray Searle, own Double S Farms. They grow potatoes for the fresh market, and grains, on about 1,000 acres.

In a May 6 letter to Double S, USDA’s Animal and Plant Health Inspection Service said the field “has successfully completed the deregulation protocol, a stepwise series of tests to demonstrate that the PCN infestation has been fully eradicated, allowing it to be released from federal regulation for PCN.” The letter applies to state and federal regulation.

The release of the 125-acre field from regulation dropped Double S Farms’ quarantined area to 75 acres, Bryan Searle said.

“The way that was done was through relationships Double S has” including with UI researchers, private crop consultants, the Idaho State Department of Agriculture and the state Potato Commission, he said. Through these relationships, a biofumigant formulated for canola elsewhere was put to use successfully.

“We’re hopeful this also can benefit other quarantined acres to also go down that path and be released from quarantine,” said Searle, who is Idaho Farm Bureau Federation president.

Animal and Plant Health and the state agriculture department regulate infested fields where the nematode has been confirmed, and associated fields that may have been exposed to infested soil in the past such as by moving farm equipment between fields, according to APHIS.

APHIS periodically releases from regulation associated fields, but releasing an infested field, which must pass several rounds of tests, is rare, a USDA spokesperson said.

A greenhouse bioassay tests the nematode’s ability to hatch, feed and reproduce when cysts are placed near a growing host plant in a controlled environment. Fields must undergo three rounds of greenhouse bioassay to advance to the final deregulation stage: in-field bioassay.

At Double S Farms, the most recent effort to release the 125-acre field — leased from a neighbor in 2006 and found to have PCN after the Searles harvested their first crop there — lasted seven to eight years. Once during this period, they were progressing through the multi-year process but had to restart after a detection.

In mid-November, APHIS removed 42.8 acres from the regulated area in Bonneville County, Idaho, because PCN-associated fields completed a release protocol, according to an announcement from the agency. That left the regulated area in the state at just over 6,452 acres — 3,538 in infested fields and 2,914 in associated fields. At the time, the infested fields were in an 8.5-mile radius that spans a portion of northern Bingham County and southern Bonneville County.