Soybean cyst nematode management and sampling
Now is the time to consider having a free soybean cyst nematode diagnosis on soybean fields as they are harvested this fall or on wheat fields going into soybeans next year.
The soybean cyst nematode (SCN) causes more yield loss than any other soybean disease in North America. In Michigan alone, SCN causes more than $40 million of economic losses per year.
There are multiple tactics for managing SCN
Because of the significant damage that SCN causes, effective solutions are essential. There are several management practices, with some practices more effective than others:
- Test soil and know SCN numbers and SCN type (ability to reproduce on a source of resistance).
- Have good sanitation practices (prevent soil movement) if a field does not have SCN (prevention).
- Rotate with non-host crops such as corn, wheat, and most non-leguminous crops.
- Rotate sources of resistance (i.e., Peking and PI 88788).
- Promote soil health with inputs such as manures applied during years of non-host rotations (i.e., corn or wheat), non-host cover crops.
- Consider using seed treatments.
Soil testing tips
Farmers in soybean producing areas of Michigan can receive free SCN diagnosis thanks to farmer checkoff funds from the Michigan Soybean Committee.
- Use a cylindrical soil probe to collect samples.
- Collect samples at a depth of 6-8 inches deep, making sure to sample in the row.
- Collect 20 samples in a zigzag pattern. Place the samples in a plastic bucket and mix thoroughly for a composite sample. Research shows that 20 well-taken samples per composite will result in more repeatable test results compared to samples with five to 10 samplings per composite.
- Sample fields according to soil texture zones.
- Take the composite soil sample and place about 1 quart of it in a plastic bag. Store in a cool area away from sunlight until shipment can be made to the laboratory.
The Michigan Soybean Committee completely covers the costs of laboratory analyses for soybean cyst nematode monitoring through Michigan State University Plant & Pest Diagnostics. Please use the form when you submit your sample. You can also see instructions on how to take and submit soil or root samples.
In addition, you can request for an evaluation of your SCN type since many SCN populations overcame the resistance found in commonly used PI 88788 varieties. Evaluation of SCN type can be requested in the form you will submit with your sample.
What to know about rotating different sources of resistance:
- It is most effective to rotate sources of resistance (i.e., Peking and PI88788).
What to know about rotating to non-host crops:
- It is important to rotate with non-host crops such as corn and wheat. Most non-leguminous crops are non-host. Do not rotate with dry beans or other legumes.
- The first year of non-host rotation is the most effective in reducing SCN. It has been observed that farms that have both corn and wheat (compared with corn alone) in the rotation have lower incidence and numbers of SCN.
Nematode-protectant seed treatments
- If they are used, they need to be used in conjunction with other management strategies (i.e., non-host crops rotation, and rotation of sources of SCN resistance).
- They are a tool but based on literature reviews and trials, they generally do not reduce numbers enough to use as a stand-alone management practice. Rotation with a non-host crop and rotating sources of resistance are both more effective management strategies, so a combination of these tools is important.
Of the methods described above, prevention and monitoring, crop rotation with non-hosts, using SCN resistant varieties and rotating different sources of SCN resistance are the most effective management practices.
While genetic resistance is one of the most effective control tactics against SCN, many SCN populations have adapted to the commercially available sources of resistance. Knowing the SCN type can allow you to select a soybean variety with greater yield potential, even in fields with high SCN levels. Still, to maintain the effectiveness of these genetic traits, multiple management strategies such as rotating different sources of resistance should be implemented.
The MSU Department of Entomology Nematology lab’s SCN rotation trials have found that:
- Rotating soybean cultivars derived from Peking and PI88788 sources of resistance can lower SCN population densities.
- Continuous use of PI548402 (Peking) or PI88788-derived varieties or including SCN susceptible soybeans in the rotation increased SCN densities.
- Rotation with Peking and PI88788 derived varieties resulted in higher yields in 2018–2020, compared to continuous use of the same varieties.
- A Michigan SCN population from continuous cropping of PI88788 derived cultivars was able to reproduce on Peking derived soybean cultivars.
Read the complete paper with further details regarding use of rotation for SCN management: Soybean cyst nematode (Heterodera glycines) resistant cultivar rotation system impacts nematode population density, virulence, and yield.
This article was originally published in The SCN Coalition Newsletter.