University of Wisconsin-Madison Partner
SCN is important in Wisconsin because:
- About 25% of Wisconsin’s soybean fields are infested with SCN with new finds every year.
- SCN has already spread to 57 counties so every field in Wisconsin has the potential to become infested.
- No farm in Wisconsin has been successful in eradicating SCN.
- Yield loss due to SCN has been documented in Wisconsin for over 25 years.
- The Wisconsin Soybean Marketing Board sponsors free soil testing for SCN.
SCN Management Recommendations
There are multiple tactics for managing SCN:
- Rotate soybean with other crops to break the SCN life cycle.
- Plant SCN-resistant varieties to reduce SCN reproduction.
- Shepherd host resistance to preserve its efficacy.
- Boost resistant varieties with an effective SCN seed treatment if needed.
- Rest fields from soybean if SCN population densities are very high.
Soil testing tips:
- Where in the field: For detection, collect soil from areas with low yield, high pH, excessively weedy or at field entrances. For monitoring the status of known infestations, follow a zig-zag pattern across the entire field to collect soil.
- When: Sampling in the fall is preferable, but SCN are permanent residents that can be recovered from soil at any time.
- How often: Sample every 3 soybean crops or sooner if yields begin to disappoint or patchy areas of stunting become apparent.
Request a free soil sampling kit!
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What to know about rotating different resistant varieties:
- SCN remodels soybean root cells into nematode feeding sites.
- Resistant plants don't allow SCN to remodel the cell.
- The source of resistance, like PI 88788, determines the general plan of resistance deployment, but even varieties with the same source of resistance affect nematodes in different ways
- Rotating varieties is a good way to obstruct the few exceptional nematodes able to slip through a particular resistant soybean defense.
What to know about rotating different sources of resistance:
- For the average Wisconsin population of SCN, 1 out of 5 nematodes can reproduce on PI 88788, the source of resistance for most commercial soybean varieties sold in the state.
- The ability to reproduce on PI 88788 is a heritable trait that becomes more prevalent in a population every time a variety with that resistance is grown.
- Sources of resistance other than PI 88788 are available for Wisconsin.
- Rotating different sources of resistance in a field maintains diversity within the SCN population so those nematodes able to reproduce on PI 88788 remain a minority.
What to know about rotating to non-host crops:
- SCN reproduction harms this year’s crop and contributes to the reservoir of SCN eggs in the soil for future crops.
- The soil reservoir of SCN eggs is depleted in years that corn, small grains, or other non-host crops are grown.
- Research in Wisconsin showed the rate of decline for the egg reservoir to be highly variable among fields, ranging from less than 1% to 50% reduction per year. Practices that promote soil health, particularly those that increase soil organic matter, are thought to be conducive to egg mortality in non-soybean years.
Nematode-protectant seed treatments:
- SCN-control using nematode-protectant seed treatments has proven variable in Wisconsin.
Other need-to-knows about SCN:
Root Lesion is a very common pest of soybean in Wisconsin. High population densities of Root Lesion have been associated with a 3-5% yield loss for soybean. Unlike SCN, Root Lesion has an extremely wide host range that includes vegetable as well as grain crops. Managing Root Lesion during the soybean year benefits yields throughout the rotation. The free testing program in Wisconsin tests for Root Lesion as well as SCN.