Soybean cyst nematode is a microscopic roundworm that feeds on roots. Since it was first discovered in the US in 1954, the nematode is now present in every state where soybean is grown. Long-distance dispersal of SCN depends on the movement of infested roots and soil on ag equipment, tires, shovels, animals, runoff water, etc.
Once the nematode is established in a field, hundreds of eggs will survive in the soil for many years in structures called cysts (dead SCN female bodies), even in the absence of a host. A factor that may have contributed to the widespread distribution of SCN across the US is that it may be present in the field without causing symptoms. When everything looks fine, there is no reason to test soils for nematodes or take extra time cleaning tires and ag equipment.
In Pennsylvania, SCN has been officially confirmed in York and Lancaster counties. Furthermore, at least one field in four additional counties must be re-tested to be confirmed positive for SCN. Although severe losses due to SCN have not been reported in PA, in areas where SCN in prevalent infestations can lead to yield losses up to 50%.
Can anybody afford to lose so much yield? SCN distribution in PA can be wider than what we know. To be proactive, all farmers should be testing their fields.
How do you test your fields?
Soil samples for SCN can be taken anytime during the growing season if there is suspicion of nematodes affecting your crop. In the Fall, it is easier to take soil samples right after harvest with a soil probe, a hand trowel, or a shovel.
There are different approaches to collecting samples. For example, large fields can be subdivided into 20-acre segments and samples collected in a zig-zag pattern within the rows and 6-8 inches deep. Samples can also be collected from different management zones within the farm, like hillsides or along waterways.
Sampling can target areas considered high risk, including field entryways, previously flooded areas, areas prone to flooding, low-yielding spots, around buildings where equipment is stored, and high pH areas. Collect at least 20 cores per 20 acres or smaller areas.
Once you have collected 20 soil cores, place them in a bucket, break them into fine soil particles, and mix them well. Pour two pints of soil into a soil testing bag or a sealable plastic bag. Label the bag with your name, phone and email, address, date, current crop, and the number of acres.
Samples can also be taken in the spring, however, if you suspect you have SCN in your field, having your soils tested earlier can help you determine what management practices to implement in case the result comes back positive for SCN.
Where do you send the sample?
Thanks to the support from the PA Soybean Board, free soybean cyst nematode testing is being offered to all soybean growers in Pennsylvania.
Send the sample to the following address:
Dr. Dilooshi Weerasooriya,
Department of Plant Pathology and Environmental Microbiology,
211 Buckhout Lab.
The Pennsylvania State University,
University Park, PA 16802.
Phone: 814-863-4798.
We will contact you to get information about the field and previous crops. If you have questions about the free testing program, feel free to contact Adriana Murillo-Williams (axm1119@psu.edu), Paul Esker (pde6@psu.edu), or Alyssa Collins (aac18@psu.edu). You can also contact your local Agronomy Extension Educator for more information about the sampling program.
For more information about soybean cyst nematode, visit The SCN Coalition website.
