By Emmanuel Byamukama, Extension Plant Pathologist

Is your yield monitor indicating low yielding areas in your soybean field? SCN could be the problem. Get to the root of the problem by testing your soil for the soybean cyst nematode.

Soybean Cyst Nematode (SCN)

The soybean cyst nematode can cause soybean yield loss without causing obvious above ground symptoms. The nematode infects soybean through the roots (Figure 1) and sucks nutrients that would otherwise be used by the plant. Worse still, the wounds created by the nematode as it enters the soybean root can lead to root rots caused by fungal pathogens.

SCN is spread by anything that moves infested soil around including farm machinery, wild animals like deer and geese, water and wind erosion, etc. Once SCN is established in a field, it is practically impossible to eradicate it. However, it can be managed to keep the numbers in check.

SCN Management

SCN management starts with a soil test to determine the presence or absence of this nematode in the soil. Absence may indicate either the SCN has not established in the field or could be present in non-detectable levels. Therefore there is a need to keep testing the soil every so often (such as every three years). A positive SCN detection requires adoption of an integrated management approach that includes planting resistant cultivars, crop rotation with non-hosts, and use of nematicide seed treatments especially for fields where SCN egg counts are very high (>10,000 eggs/100 cc of soil). It should be noted that the effectiveness of nematicide seed treatments has not been consistent across the region.

Soil Testing

Use of a soil probe or a spade/shovel to obtain 20 cores of 0-8 inches of top soil from 15-20 acre sections of the field. Target areas should include field entrance, persistently low yielding areas, low spots, and along the fence line.  Mix the soil thoroughly and put a pint of soil into a SCN sample bag or the soil fertility test sample bag.