BURLEY, ID – A nearly invisible pest is gaining a foot hold in grain fields across the Northwest.
Nematologists first identified cereal cyst nematode in western Washington in 1974. But the pest wasn’t widespread nor did it seem to cause much economic loss and so researchers focused their attention on nematodes in high value crops where the damage was greater.
Now cereal cyst nematode is found in at least seven states and some estimate it costs grain producers in Oregon, Washington and Idaho at least $3.4 million each year.
Dick Smiley thinks the problem is bigger than those estimates. He is a plant pathologist at Oregon State University who has been studying cereal cyst nematode (CNN) since the mid-1980s. He started studying the pest because he thought it was being overlooked and was likely associated with fungal diseases he was also researching.
The estimates are based on soil samples submitted by farmers. Farmers usually don’t soil sample their dryland fields as often as irrigated fields so dryland production is under represented, Smiley said. Even when dryland samples are sent, the laboratory isn’t likely to pick up CCN unless the grower specifically asks the lab to look for it. Nematode identification is an extra charge so only growers who think they have a problem will ask.
Nonetheless, Idaho now has several counties where the CCN population is so high that it is easily found in even regular soil samples. Most of those counties are found in south eastern Idaho, but the Magic Valley is not in the clear. Power County, located just east of Cassia County, is one of those hot spots.
“If you can’t explain pock marks in a field and you suspect cereal cyst nematode, you must sample inside the patch,” Smiley said. “Failure to detect nematode species does not mean the field is cyst-free.”
Smiley told grain producers during the University of Idaho’s annual cereal school in Burley that it’s easy to be complacent about CCN.
“For the first decade after it’s introduced you won’t see any damage, but it will continue to spread.” As infested patches grow, the damage adds up.
Fortunately, the pest is host-specific so it doesn’t affect broadleaf crops such as potatoes or sugar beets that already have nematode problems as it is. Unfortunately, wheat, barley and oats are all susceptible and continuous spring wheat is the most vulnerable.
CCN larvae penetrate the rootcap of newly emerging roots leaving behind a bushy or knotted root system. Because the roots are so damaged, the plant can’t take up nutrients or water.
Smiley often gets called out to fields that aren’t responding to nitrogen or appear to be droughty even under irrigation.
Spring wheat is more vulnerable than winter wheat because the nematode has a one-year life cycle. The larvae emerge around March 1 and by early May have moved into root systems.
Winter wheat has established a good root system before the larvae begin feeding, unlike spring wheat or barley that is germinating at the same time larvae are emerging.
Extending he rotation between grain crops and including a broadleaf crop in the rotation is key. Smiley’s research indicates growing a continuous grain crop yields about half of the yields realized by growers who use a three-year crop rotation.
Trials at St. Anthony, Idaho, using a potato-wheat rotation have shown that one year of potatoes is not enough to reduce the CNN population. Growers should have at least a two-year rotation, Smiley said.