What Does SCN Damage Look Like?

Soybean producers frequently ask, "What does SCN damage look like in the field?" The answer is not simple and requires a professional diagnosis for these reasons:
 
 
  1. symptoms of SCN infections can range from no visible evidence of plant injury to plant death in certain areas of the field,
  2. the symptoms commonly associated with SCN damage are similar to other crop production problems such as potassium and nitrogen deficiencies, iron chlorosis, herbicide injury, soil compaction, drought stress, and other soybean diseases,
  3. the white (or yellow) female is the only visible sign of SCN infection, but they may not be present at the time of sampling. Cysts (brown females) are not visible in soil.
In high-yield production fields (greater than 40 bushels/acre) or during years when soil moisture from rainfall or irrigation is plentiful, visible symptoms of SCN damage are rarely seen. Research has shown however, that yield losses of 15 to 30% on a susceptible variety are common in these fields. Soybean farmers in these situations often notice poor or static yields over several years, uneven plant height in the field, or a delay in canopy closure. This lack of apparent symptoms is more commonly associated with soybean grown in the midwest where soils tend to be more fertile and growing conditions less stressful on soybean.

 White female SCN are most readily seen in the field when the soybean plant begins to flower. The feeder roots must be carefully dug up in the field with a shovel and the soil gently removed or the females will be dislodged. Although observation of white females will confirm an SCN infestation, it cannot tell you much about the level of infestation. Also, if you dig up roots and don't find white females, that does not mean that SCN is absent. The only way to get a reliable diagnosis is through a professional diagnostic laboratory (see Soil Sampling for SCN, page 11).

The white females of SCN may be detected around the time of flowering, if the roots are dug carefully.

Soybean damage due to SCN is frequently misdiagnosed. Reduce your risk of loss by submitting soil samples for professional diagnosis.