Soybean cyst nematodes are small, nearly microscopic roundworms that infect soybean roots. You can see them clearly in this picture. One caution, be careful to not confuse the nematodes with the larger, nitrogen-fixing nodules.
Soybean cyst nematode is the most serious soybean pest in the United States, costing farmers an estimated $1 billion-plus in yield losses each year.
If you don’t know whether the small but fierce soybean cyst nematode (SCN) lurks in your fields, damaging your crop potential, now is a good time to figure that out. The reason: this little pest costs farmers millions of dollars each year. It stunts soybean root growth, impairs root translocation of water and nutrients, strips nutrients from soybean plants, reduces nitrogen fixation and makes soybean roots more susceptible to soil-borne plant pathogens.
Furthermore, SCN is involved in the development and spread of Sudden Death Syndrome (SDS), according to Missy Bauer, Associate Field Agronomist for Farm Journal.
"Research has shown that SCN hastens the development of SDS symptoms and increases their severity, leading to extensive yield loss," Bauer says.
Bauer shared her research on SCN with farmers attending the 2013 Farm Journal Soybean College in Coldwater, Mich., earlier this week.
While farmers can test for SCN populations just about any time, early fall is the best time to check fields. "We’ve found that soil samples taken following harvest provide the highest population numbers," Bauer reports.
For sampling purposes, she says:
1. Use a cylindrical soil probe to collect soil samples. Collect the soil cores at a depth of 6 to 8 inches deep, and be sure to include plant roots. "Don’t pull the roots, dig them up so you don’t knock any of the SCN off," she says.
2. Collect 10 to 20 soil cores by walking in a W pattern across the field or area to be sampled.
3. Submit one sample for each 10-acre field or for an acre you suspect is infected by SCN. "Don’t go to the middle of a hotspot to pull a soil sample," Bauer cautions. "In the worst part of the hotspot there’s usually not a good root system present, so we want to pull samples from the outside fringes where the root system is still in pretty good shape."
4. Use a plastic sandwich bag to hold the samples. "We want to keep these nematodes alive until they reach the laboratory, so put them in a plastic bag so they don’t dry out and die," Bauer explains. "We carry coolers with us and keep the samples in there and then ship them to the lab via UPS that day or put them in the fridge overnight them the next day. Whatever you do, don’t put them on your truck and drive around for two days before you send them to the lab."
State university laboratories and independent laboratories can test for SCN. Bauer adds that some state universities offer free sampling through soybean checkoff programs, including Michigan and Illinois.
If test results show moderate to high levels of the pest are present, Bauer encourages farmer to manage those populations via a variety of measures the following season, including:
• Resistant soybean varieties
• Crop rotation
• Non-host crops
• Biological controls
• Changes in tillage practices
• Stress reduction (i.e. reduce weeds, address fertility issues)
Thank you to the 2013 Soybean College sponsors:
Agrotain, BASF, Great Plains Mfg., Novozymes, Plant Tuff, Precision Planting, SFP, Wolftrax
Catch up on full coverage of Corn and Soybean College at FarmJournalCornCollege.com.