A microscopic parasitic roundworm is costing Pacific Northwest wheat growers $51 million in lost revenue each year because it cuts grain yields by about 5%, Oregon State University researchers warn.
The root lesion nematode lives in the soil and feeds on roots of wheat, barley, oats and other crops. It limits the ability of plants to absorb needed nutrients and water from the soil, causing yellowing of leaves and smaller grain heads.
"Presence of nematodes is usually confused with root rot, viruses or lack of nutrition because the effect on crops looks the same," explains Dick Smiley, an OSU plant pathologist at the Columbia Basin Agricultural Research Center in Pendleton.
"But nematodes often go undetected because they're not well known, and because they're transparent and thinning than a human hair."
Researchers have detected the rook lesion nematode in most fields sampled in Idaho, Oregon, Washington and Montana. Population densities of nematodes high enough to reduce yields have been detected in 60% of sampled fields in Oregon and Washington.
The worms are most active in dry areas where wheat and barley are produced.
Most nematodes are beneficial to ag by helping decompose organic matter, but some are parasitic to plants and spread easily via the wind, on animals, or by hitching rides on equipment and boots.
It is considered all but impossible to get rid of the pests once they have become established in fields.
Another harmful nematode, the cereal cyst variety, is estimated to cause nearly $3.5 million in losses to farmers per year in the Pacific Northwest.
OSU researchers are studying crop management strategies to mitigate the impact of the worms, but to date have only found that a three-year crop rotation – skipping wheat for two years -- works best.
Root lesion nematodes, they say, are well managed by planting winter wheat the first year and spring barley the second, then fallowing the field for the third year.