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Soybean Cyst Nematode
Soybean Cyst Nematode (SCN) is a worm-like organism in the animal kingdom that parasitizes plant root tissue. This pathogen has not yet been reported in North Dakota but is known to occur in counties in Minnesota and South Dakota that border our state. This is the time of year when symptoms may become evident. They are only visible on above-ground parts of soybeans when the pathogen population has built up to a significant number. It is particularly important for growers in the southeast part of the state, near to South Dakota and to Minnesota, to scout for symptoms and have any suspicious fields checked. This can be a devastating pathogen if left unchecked; however, it is quite manageable if the grower is aware of the problem and uses appropriate rotation and variety selection.
The host range for this pathogen includes susceptible soybeans, dry and snap beans, peas, and susceptible forage crops such as Sweetclover, Vetch, Lespedega, and Birdsfoot trefoil It is called a cyst nematode because the female nematode feeds on the roots, swells, and fills with eggs. As the female matures and dies, she turns a brownish color. This stage is referred to as the cyst, which can survive in the soil and from which eggs are hatched.
Symptoms of SCN usually begin to express themselves later in the season, and only show on above ground parts of the plant. Symptoms may appear similar to iron chlorosis, compaction, drought stress, other nutrient deficiencies, and herbicide injury. Symptoms of possible nematode problems will show up on oval or circular areas on a field, often in an elongated shape that follows tillage patterns. Unlike iron chlorosis where the whole leaf expresses interveinal yellowing, SCN will cause the outer margin of the leaf to yellow and brown, and eventually the whole leaf is affected, not just the area between veins. Plants are usually stunted and rows may not close in affected areas. Symptoms are usually more severe in the center of the affected area and decrease in severity toward the margins. These affected areas are more common at field entrances, where equipment may enter, and along field edges where windblown soil may accumulate. Cysts move most often in soil and soil-peds in seed, and on equipment that might carry soil from an infested field to a new field. Damage is generally more severe on light, sandy soils, but other soil types can be affected as well. It is not uncommon to have both iron chlorosis and SCN symptoms on the same plants.
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