Scope of problem in Northwest hard to determine
By JOHN O'CONNELL
SUGAR CITY, Idaho -- It took Roy Jeppesen and his crop advisers a season and a half to diagnose the reason for his declining wheat yields.
Last harvest, healthy portions of his irrigated crop produced roughly 110 bushels per acre, while sickly patches yielded about 40 bushels per acre.
In early June, University of Idaho Extension cereal pathologist Juliet Marshall identified the culprit as the cereal cyst nematode, a persistent pest that's taking a more noticeable toll on drought-stressed crops in parts of the Pacific Northwest this season.
Robb Orr, who assists Jeppesen on behalf of Valley Wide Co-op in Rexburg, initially attributed the poor yields to a tillage or soil compaction problem. Orr has since confirmed cases of the nematode in other clients' fields in the region.
Marshall suspects the nematode is far more widespread than growers realize, especially in Idaho's Rexburg and St. Anthony areas, where they can find the sandy soils they like. The scope of the problem has been tough to ascertain due to growers' reluctance to pay for a costly soils test, or their lack of awareness.
After taking the field out of barley, Jeppesen planted it to wheat for three consecutive seasons. He'll now consider switching to alfalfa, which doesn't support the nematode; barley, which tends to maintain favorable yields despite infestations; or mustard or radish, which chemically reduce nematode numbers.
"At least now I know what I'm dealing with," said Jeppesen, who farms north of Rexburg in Sugar City.
The good news for growers is that in late July researchers identified a hard red spring variety called WestBred Rockland that appears to be resistant and is already gaining popularity in Eastern Idaho.
For the past three years, Marshall has collaborated with Dick Smiley, a plant pathology professor with Oregon State University's Columbia Basin Agricultural Research Center in Pendleton, Ore., on cereal cyst nematode resistance field trials involving 20 spring wheat varieties. The trials have been conducted on dry land in Eastern Washington and both irrigated and dryland plots in St. Anthony.
WestBred Rockland, which will likely be used in breeding other resistant varieties, supported one cyst per plant root system at St. Anthony, comparable to an Australian variety in the trial known for its resistance to the nematode. A highly susceptible variety, the hard red Westbred 936, supported 25 cysts per root system. Each cyst contains hundreds of eggs. Chemical treatments Marshall and Smiley have tested to control the nematode, however, haven't led to immediate yield improvements.
Wheat plants in infested fields tend to have knotted roots. Smiley said a two-year rotation away from wheat seems to have little effect on nematode populations.
Smiley said seven Western states have the nematode, which causes an estimated $3 million in combined farm gate losses from known infestations in Idaho, Washington and Oregon. Eastern Washington, especially Whitman County, has been hard hit by the nematode. Oregon's greatest cereal cyst nematode pressure is in the eastern part of the state in Union County, Smiley said.
Nematodes are tiny, unsegmented roundworms. Cereal cyst nematodes can survive without a host in soil for years and are nearly impossible to eradicate, Smiley said.