Production Blog: SCN Thrive in Drought

Nematodes are nasty. The dirty, double-crossers work behind the scenes, stealing what they can and sometimes when you least expect it. These bullies of the soybean field even thrive in drought conditions, which seems low-down, even for a pest.

Since so many areas of the Soybean Belt are struggling with dry conditions this fall, DTN asked Horacio Lopez-Nicora, soybean pathologist and nematologist at Ohio State University, to explain more about SCN under dry conditions and what farmers should consider going into 2026. Here are his answers.

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Q: Does SCN thrive in drought conditions?

A: Yes. SCN tends to be more problematic during hot, dry years. While SCN doesn't necessarily "prefer" drought, drought conditions accelerate its life cycle, allowing it to complete more generations in a single growing season. This leads to higher population densities and increased egg counts by fall soil sampling.

Importantly, the stress that drought places on soybean plants also amplifies the damage caused by SCN, making symptoms more visible and yield losses more severe.

Q: Does the SCN life cycle speed up during drought?

A: Yes. Under optimal soil temperatures (around 75 to 82 degrees Fahrenheit (23-27 degrees Celsius)), SCN can complete its life cycle in 21 to 28 days, and drought conditions often coincide with these warmer soil temperatures. This means multiple generations (three to six) can occur in a single season, especially in drought years.

Q: Do we know the mechanism behind accelerated reproduction in drought?

A: Currently, the exact physiological or molecular mechanism is not fully understood. While reproduction clearly increases during drought, the mechanistic basis remains unknown.

Hypotheses include:

-- Warmer soil temperatures speeding up juvenile development.

-- Reduced microbial competition or changes in soil biota under drought.

-- Plant stress responses potentially altering root exudates, which may influence nematode behavior.

However, these remain speculative and should be/are active areas of research.

Q: What does this mean for SCN management strategy in 2026?

A: Following a drought year, SCN populations are likely elevated, so proactive management is critical.

Recommended strategies include:

-- Soil testing: Fall soil sampling is essential to determine SCN egg densities and guide decisions for 2026.

-- Crop rotation: Rotate to non-host crops (e.g., corn, wheat, alfalfa) to reduce SCN populations.

-- Resistant varieties: Use SCN-resistant soybean varieties, but rotate resistance sources (e.g., PI 88788 vs. Peking) to delay resistance breakdown.

-- Seed treatments: Consider nematode-protectant seed treatments to reduce early-season infection and promote overall root system health, which can enhance plant resilience under stress conditions.

-- Monitor trends: Continue annual soil sampling to track SCN population changes and adjust management accordingly.

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Read more about SCN in "Fascinating Facts About Soybean Cyst Nematode," https://www.dtnpf.com/….

National Nematode Day is Oct. 6, an effort to increase awareness of this yield robbing pest. Find a library of resources from The SCN Coalition here: www.TheSCNCoalition.com. The SCN Coalition is a public/checkoff/private partnership formed to increase the number of farmers who are actively managing SCN. Partners in The SCN Coalition include university scientists from 28 states and Ontario, grower checkoff organizations, including the North Central Soybean Research Program, United Soybean Board and several state soybean promotion boards, and corporate partners including BASF, Bayer, Growmark, Indigo, Nufarm, Pioneer (Corteva), Syngenta, Trace Genomics, UPL Ltd., Valent and Winfield United.

Pamela Smith can be reached at pamela.smith@dtn.com

Follow her on social platform X @PamSmithDTN

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