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SCN is important because:
- SCN is widespread in soybean production areas of Virginia.
- In a typical year, SCN causes more yield loss in soybean than any other disease.
- SCN in fields increases the incidence and severity of several soil-borne diseases.
- Shorter rotations out of soybean have led to increased populations of SCN and other nematodes.
- Limited use and availability of nematicides have led to increased populations of SCN and other nematodes.
- SCN populations in Virginia have overcome major sources of genetic resistance in soybean varieties.
SCN Management Recommendations
There are multiple tactics for managing SCN:
- Sample fields regularly – you cannot manage SCN populations unless you know your numbers.
- Integrated management is key – use a combination of cultural practices, host resistance, and seed-treatment nematicides.
- Crop rotation is the best option for reducing nematodes – rotate out of soybean to reduce SCN populations.
- Rotate varieties – if possible, do not rely on a single source of genetic resistance.
- Seed treatment nematicides – alone these may not provide adequate control, but they can be useful as part of an integrated management strategy.
Soil testing tips:
- Where in the field?
- Problem areas can be targeted for initial sampling, but for predictive assays (which are used to make management decisions for the next year’s crop), sub-samples should be taken from throughout the field.
- For every 10 acres, a minimum of 20 composite soil cores should be taken in a zig-zag pattern from the root zone at a 6 inch depth. If a field has multiple soil types, collect a separate sample from each area.
- When? Predictive assay samples should be taken in the late summer or early fall near harvest.
- How often? In SCN infested fields, nematode samples should be taken regularly to determine how management practices are impacting SCN populations.
- Where should soil test samples be sent?
- Nematode Diagnostic Laboratory
Virginia Tech Tidewater AREC
6321 Holland Road
Suffolk, VA 23437
- Nematode Diagnostic Laboratory
What to know about rotating different resistant varieties:
- Resistant varieties vary in yield potential and the ability to suppress nematode reproduction - check with your seed dealer and local Extension Specialists to determine the best variety for your cropping situation.
- Soybean varieties do not have complete resistance, and SCN populations can adapt and begin to reproduce on a specific variety over time.
- Since SCN populations can adapt to specific varieties, it is important to rotate to a different resistant variety (even if it has the same genetic source of resistance) to slow down the process.
What to know about rotating different sources of resistance:
- A majority of SCN resistant varieties have a single source of genetic resistance (PI 88788, often referred to as “race 3” resistance on the seed package).
- SCN populations can adapt and overcome specific sources of genetic resistance over time.
- When available, varieties with PI 88788 resistance should be rotated with varieties containing alternate sources of resistance (e.g. Peking or “race 1”).
- HG-typing of SCN field populations can be used to determine which sources of genetic resistance will be effective – contact the Nematode Diagnostic Laboratory for more information.
What to know about rotating to non-host crops:
- Corn, sorghum, wheat, barley, cotton, peanut, and grass forages are all non-hosts for SCN.
- For rotation to work, soybean should not be grown for at least a year (i.e. do not plant double-crop soybean after wheat).
- To determine the effectiveness of rotating to a non-host crop, be sure to sample the field and determine SCN numbers at the end of the growing season.
Other crops that can host SCN:
Some cash crops and cover crops may be hosts for SCN. These include edible beans and some vetches and clovers. In addition, SCN can reproduce on some common weeds.
What you should know about nematode-protectant seed treatments:
- Though they can be incorporated into a nematode management plan, growers should not rely solely on seed-treatment nematicides to control SCN.
- Seed treatments may increase stand establishment and early season vigor.
- Seed treatments are unlikely to reduce SCN numbers at the end of the season.
- Seed-treatment nematicides are currently being evaluated in the mid-Atlantic region. Check with your Extension Plant Pathologist for additional recommendations.
Other need-to-knows about SCN:
- To successfully overcome yield suppression due to SCN, active management is required.
- Nematode management is complex, but your Extension Specialists are here to help!