Fighting the Hidden Killer: Top Management Tips to Control Nematodes in Soybeans

soybean field

Key Takeaways

  1. Nematodes have long been a leading yield robber in soybeans, but this yield-robbing pest is becoming even more of a threat as resistance issues grow.
  2. Almost all soybean growers face nematode pressure, but not all realize the damage the pest is doing to their fields, since there may be few or no above-ground symptoms. It’s critical that growers integrate multiple management practices to protect their crops.
  3. ILeVO® seed treatment from Bayer offers advanced protection against nematodes. On average, growers are seeing a 2- to 4-bushel-per-acre* yield advantage with ILeVO under low to moderate nematode pressure.

If it seems like your soybean yields are plateauing, you’re not alone. When Iowa soybean grower Ron Heck started noticing his yields seemed “off,” the culprit surprised him.

“I knew there was yield variability in my ­fields, but I had no idea how large it was,” said Heck, a former American Soybean Association president who has farmed for 44 years near Perry, Iowa.

Heck partnered with Iowa State University researchers to find answers. “We were all surprised to ­find out that soybean cyst nematode (SCN) was a major contributor to the yield differences,” Heck said.

Destructive nematodes like SCN can slash soybean yields by 30 to 50 percent – all without any above-ground symptoms. These microscopic, parasitic roundworms wreak havoc by penetrating the vascular tissue in plant roots, feeding on cell material and blocking nutrient uptake.

“While insects and weeds are visible pests, nematodes quietly attack your yields and profi­ts without drawing much attention,” Heck said.

SCN is a serious challenge, but it’s not the only nematode threat. Other pests include root-knot nematodes and reniform nematodes, which are among the most destructive nematodes in the southern United States, especially in cotton-producing areas. Root-knot nematodes induce globular, irregularly shaped galls on soybean roots. These galls can be distinguished from soybean plants’ nitrogen-­fixing nodules, which are spherical in shape.

Many farmers don’t realize that their soybean ­fields have been invaded by nematodes. These pests can feed off soybean roots for weeks before any above-ground symptoms appear. By then, nematode populations have grown more numerous and much stronger, becoming dif­ficult to control.

The practice of growing SCN-resistant soybean varieties is considered to be the most effective tool for the management of SCN, but it is far from a complete solution. Continued use of the soybean varieties that utilize the same source of SCN-resistant genes (PI 88788) has led to the increased ability of SCN to adapt and reproduce. As with herbicide resistance, reliance on a single SCN-management tool has reduced the technology's effectiveness as the target pest has evolved.

Once in a field, SCN cannot be eliminated, making it essential to actively manage this pest with multiple strategies.

Active Management is Essential

The cornerstone of a nematode management program starts with soil sampling. “We’ve got to sample to know what’s going on below ground, because an above-ground inspection is not going to tell us what’s going on with nematode populations,” said Jason Bond, a professor and plant pathologist at Southern Illinois University.

The use of these management strategies should be integrated to reduce nematode populations and damage, while maintaining soybean yields:

  1. Put a rotation plan in place.
    Planting a non-host crop, such as corn, wheat or sun‑flowers, can help reduce nematode populations in your ­yield, especially SCN.
  2. Plant an SCN-resistant soybean variety.
    Seek out higher levels of nematode resistance and diverse sources of nematode protection in soybean varieties, such as Peking genetics.
  3. Investigate new seed treatments.
    While nematode resistance is evolving, so are modern seed treatments that complement resistant soybean varieties. Seed treatments offer added protection against nematodes.

ILeVO from Bayer is a broad-spectrum nematicide seed treatment that helps control many harmful nematodes, including SCN, root-knot and reniform. ILeVO is active across multiple stages of the nematode development cycle by reducing hatching eggs, decreasing juvenile mobility and development, and also by reducing nematode reproduction in the seed zone. “ILeVO provides a complementary benefit to SCN-resistant varieties by adding another level of protection to kill nematodes,” said Jeremiah Mullock, Bayer SeedGrowth™ Product Development Manager.

Seedlings that are protected right from the start develop more vigorous root systems. This leads to stronger, healthier plants that are better able to ward off yield-robbing pests as the crop grows.

“ILeVO delivers a consistent yield response in the 2- to 4-bushel-per-acre* range when targeting nematodes,” said Mullock, citing research data collected since 2011. “If you have above-ground symptoms of SDS, as well as nematodes in your ­fields, this yield advantage with ILeVO is 4 to 10 bushels per acre.*”

Using a proven seed treatment is an effective way to bring additional management for nematodes while protecting yield potential. Although there's no way to completely eradicate SCN from a field, there are ways to manage the issues and prevent substantial yield loss.

*Compared to a fungicide/insecticide base seed treatment.

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