Each year, a microscopic parasite known as the soybean cyst nematode (SCN), costs more than $1 billion in yield losses. SCN has spread to nearly all soybean producing states and continues to expand its reach abroad wherever soybeans are grown. Once in a field, the nematodes robust survival tactic means it is there to stay. The only option is to proactively manage the nematode population level through soil sampling, population typing, and the strategic deployment of resistant soybeans coupled with non-host crop rotation to reduce its impact on yield. SCN nonhost crops include alfalfa, barley, canola, clover (red, white, ladino), corn, cotton, forage grasses, oats, rye, sorghum, tobacco and wheat.
Absence of symptoms and planting of resistant soybean varieties does not mean you do not have an SCN problem. More than 80% of domestic farmland planted to soybeans is infested with SCN. The only way to know for sure if you have SCN in your field is to get an egg count test performed.
When sampling for SCN management purposes, take samples to represent the top 8 inches of soil directly at the root zone in the crop row. Soil should be collected over the entire field. Large fields should be subdivided into 10 acre sections. Collect 10 to 20 soil subsamples per section in a zig-zag pattern along the rows using a soil probe or shovel. Mix subsamples together, and send one pint-sized composite sample from each section to the laboratory.
SCN is typically not evenly distributed throughout a field. Therefore, the zig-zag sampling strategy shown below is used to collect representative soil samples. Red = high levels of SCN; Blue = low levels
When sampling for diagnostic purposes (i.e., is SCN present), collect soil from either:
Soybean roots can be carefully dug up and examined for the presence of cysts throughout the growing season. The best time of year to take soil samples for SCN is in the fall right after harvest or before soybeans are planted the following spring. Nematode levels are highest following a soybean crop and at the end of the season. High population levels will increase the chance of detecting the nematodes in your field.
We also test soil and plant samples qualitatively and quantitatively for the presence of other plant-parasitic nematodes. Follow the sampling guidelines below to collect a soil sample. Check the box for a plant-parasitic nematode identification on the sample submission form.
Sampling instructions for specific plant-parasitic nematodes
Proper collection and care of samples is extremely important. Take samples when soil is moist. Put samples in plastic bags, with the label on the outside. Do not let samples dry out! Nematodes are sensitive to heat. Keep samples in a cool, dark place until they can be mailed. Do not leave samples in the sun or other areas of high temperature.
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