Crops News

‘Let’s Talk Todes’ video series highlights impacts of SCN


The SCN Coalition wants soybean growers to understand the risks associated with higher population densities of soybean cyst nematode (SCN) during hot and dry growing seasons, like many faced during 2020.

“Weather can have a tremendous impact on soybean cyst nematode reproduction,” states Iowa State University Nematologist Greg Tylka. In a new video series titled “Let’s Talk Todes,” Tylka and North Dakota State University Plant Pathologist Sam Markell discuss how weather impacts SCN reproduction.

“We have data verifying that SCN is worse in hot, dry years,” says Tylka. “It’s not just because plants are stressed from drought, but also because the nematode is reproducing much quicker, raising population densities.”

Unfortunately, the life cycle of soybean cyst nematode speeds up during drought-like conditions. “We don’t know the mechanism of it, but reproduction happens much more quickly, creating more generations in a single growing season that ultimately leads to higher egg counts during fall soil sampling,” adds Tylka. “In areas impacted by drought with a traditional corn-soybean rotation, I would expect that in 2022, many of the fields that grew soybeans this year would have increased levels of SCN and increased yield loss.”

Other soil factors
“Soil pH and texture also impact SCN reproduction. Our first inkling that SCN reproduced well in high pH soils came after ten years of grid mapping on a central Iowa farm. That data revealed the highest pH spots in the fields had the highest nematode numbers. When you laid the soil pH and SCN maps side by side, they were in agreement nearly 85% of the time. At the time, it was counterintuitive because SCN is an obligate parasite, meaning it needs healthy plants to get the most nutrition. To have increased SCN reproduction on high pH soils where the plants are suffering from iron chlorosis was somewhat of a surprise,” Tylka said. “Soybean growers with sandy soil or sandy spots within fields should also consider those spots for soil sampling. Because those fields are so well-drained, we always see higher reproduction in sandy soil.”

Take the test

The coalition experts encourage soybean growers to test soil for SCN so they know their number and can start an active management strategy. State-specific advice is available by visiting Click on “Recommendations” and select your state in the “Coalition Experts” section.

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