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PCN find expands quarantine

Program quarantines 2,015 infested acres in 19 fields


Capital Press

Two new Bingham County fields have been added to a quarantine list in the effort to eradicate pale cyst nematode from Idaho.

The Idaho State Department of Agriculture announced in early January the fields were suspected of PCN infestation based on initial observations of soil samples made at the USDA Animal and Plant Health Inspection Service laboratory in Idaho Falls. Tina Gresham, director for the USDA's PCN program, said subsequent testing has confirmed those suspicions.

Gresham said the samples underwent further morphological assessment at a Kansas lab before heading to Maryland for more advanced measurements and DNA testing.

"There are many things that look like PCN," Gresham said.

The fields encompass 100 acres owned by different growers, Gresham said. Counting the new additions, the program quarantines 2,015 infested acres in 19 fields, all within a 5-mile radius of Bingham and Bonneville counties. Another 14,042 acres are regulated within fields that have associations with infested fields but have produced no positive samples.

"It would seem these recent detections are fields closely related to the infested fields and weren't terribly surprising to find," Gresham said.

Gresham also announced good news for the program. This season, the first quarantined field will be eligible to resume potato production, if the grower chooses. Following years of costly treatments with chemicals including methyl bromide, no viable cysts can be found in the 50-acre field. Gresham said special sanitary and testing requirements will remain in place, similar to the regulations imposed on associated fields. The field may be completely deregulated if it continues to test clean following four years of potato crops.

Five quarantined fields are undergoing greenhouse testing to determine if any cysts remain viable, prior to returning them to potato production. Results should be available by 2014.

Gresham said more than 35,000 acres of associated fields have also been deregulated, having produced two potato crops with no PCN found.

PCN, a microscopic parasite that can reduce potato yields by 80 percent, was first detected in an east Idaho tare dirt sample in 2006.

Gresham said the phasing out of methyl bromide and new buffer zones for spraying the chemical pose challenges for the PCN program. The new buffer zones, which could prevent chemical treatment of field edges near homes, won't affect this year's operations, but new strategies, such as using trap crops or biological controls, will have to be explored if the Environmental Protection Agency grants no regulatory relief for 2014, Gresham said.

University of Idaho PCN Project Director Louise-Marie Dandurand finished greenhouse trials in December that appear promising for the use of sticky nightshade as a trap crop in controlling PCN. The plant produces chemicals that induce hatching of PCN eggs but isn't a viable host for the nematodes to feed on.

In her trials, the trap crop reduced cyst viability by 70 percent. Last spring and fall, she also tested fungi that attack PCN eggs, finding one of the organisms reduced their viability by 88 percent.


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