Crop Link

Think of soybean cyst nematode (SCN) like blood pressure. You need to know your blood pressure reading to decide how to manage it.

Similarly, The SCN Coalition, a diverse group of University researchers, Extension specialists and agricultural industry, urges farmers to soil-test to manage the pest.

There’s still time to test this spring if you missed the window last fall, says Carl Bradley, University of Kentucky plant pathologist.

In general, if soybeans will be the next crop grown, he considers tests results below 2000 eggs to be low, 2001 to 12,000 eggs to be medium and egg counts above 12,000 to be high. “If corn, wheat or another non-host crop will be grown in 2019, your SCN numbers will drop, so the low/medium/high categories are higher.”

The meaning of SCN test numbers can vary by state. State-specific advice and contacts are available at thescncoalition.com.

Surveys show SCN populations are increasingly able to feed and reproduce on varieties that contain the PI 88788 source of resistance, which is used in 95% of commercial soybean varieties. Farmers who have been planting resistant varieties should not assume SCN egg counts are low.

SCN’s ability to overcome PI 88788 varies by state. In Missouri, 100% of SCN populations can reproduce on PI 88788, up from 52% in 1992. “We also see as many as six generations of nematodes reproducing per growing season,” says Kaitlyn Bissonnette, University of Missouri plant pathologist. SCN counts can elevate quickly to yield-damaging levels. Drought, such as the one experienced in Missouri last year, also increases nematode production.

To fight back, Bissonnette tells farmers in her state to soil-test to know their numbers, use crop rotation, consider a nematode-protectant seed treatment and rotate to other types of SCN resistance, such as Hartwig or Peking. Seed providers are bringing more alternative resistance sources to market but may still be hard to find. “If you can’t utilize difference resistance, at least use a different variety than you have planted in the past. Rotate within the resistance source,” she recommends.

Want to know the SCN numbers in your field? At least a dozen states offer free diagnostic testing as part of The SCN Coalition’s efforts.

Follow the latest from Pamela Smith, Crops Technology Editor, by visiting the Production Blogs at dtnpf.com or on Twitter @PamSmithDTN.

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