View From the Cab

Farmers Search for Sneaky Soybean Yield Thief

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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Zachary Grossman put his foot into the job and pulled soil samples this week to check Soybean Cyst Nematode (SCN) reproduction in his Missouri fields as part of a View From the Cab project. (DTN photo by Jason Jenkins)

DECATUR, Ill. (DTN) -- Zachary Grossman is about to find out if there's a yield thief lurking in his soybean field and how persistent the pest might be. The Missouri farmer routinely plants soybean varieties that contain resistance genes from PI 88788 to defend against soybean cyst nematode (SCN). What he doesn't know is how well the defense mechanism is working after years of using this single source of resistance.

This week he pulled soil samples that will undergo HG type testing. Traditional SCN soil tests count eggs or cysts to indicate the extent of infestation. HG type testing digs deeper to show if a SCN population can reproduce on soybean with SCN resistance and if so, the strength of that virulence.

Grossman, along with North Dakota farmers Chandra and Mike Langseth, have been filing reports each week as part of DTN's View From the Cab series. The feature is a diary-like report of crop conditions and covers other rural issues throughout the crop season.

While harvest is still underway on both farms, the farmers added SCN super sleuthing to their chore list this week. The testing project comes with support from The SCN Coalition, a public/checkoff/private partnership formed to increase the number of soybean growers who are actively managing SCN.

The Langseths are only too familiar with the threat of SCN. The farm has been soil testing for the soil-borne microscopic roundworms since they were first detected in the state in a field close to their farm in 2003.

"I'm both curious and a little anxious about the results," said Chandra. "I want to know more how our management tactics are holding up, but at the same time, we will have some hard choices if they are breaking down."

The two farms should have those answers early in 2024, but this test is labor and time intensive. SCN Diagnostics, a University of Missouri laboratory, is handling the samples, a complicated process that starts by isolating SCN from the soil. Sensitive soybeans are then inoculated with that SCN population. SCN need time to reproduce and generate a high enough inoculum for the HG type test. Finally, soybean lines with different resistant genes are inoculated with nematodes and allowed to grow for 35 days. DTN will be following the tests through the process.

Read on to learn more about the field each farmer chose to test and why. This week both farms were still grinding through corn harvest with some surprisingly good yield results. However, cold had combined with wet to bring new challenges. And, in Missouri, Grossman gives his cattle some extra calories as the temperatures dip.


Cold in late October and early November is nothing new in North Dakota, but last week's weather dished out a harsh reminder. "We had a bit of a North Dakota issue with continuing to harvest. The tail end of a rainstorm last week turned into freezing rain and then, snow," said Mike.

"We had just enough snow stuck to the corn plants that even after it quit raining, we couldn't harvest because the snow on the plants would melt on the way through the combine. It was just as bad as combining in the rain -- maybe a little worse," he added.

Hardly anyone is ever happy to see a 35-mile-per-hour wind during harvest, but in this case, the blowing shook off what was left of that sticky snow and allowed combines to roll again after five miserable days of waiting. On Nov. 2, the Langseths had approximately 75% of their corn left to combine with more rain forecast.

DTN Ag Meteorologist John Baranick said an active pattern will mean several disturbances moving through the northern half of the United States during the coming week. That could leave this area on the receiving end of some precipitation that could once again be a mix of rain and snow, Baranick noted.

What the couple isn't complain about is yields after an extremely dry growing season. The first field of dryland corn was harvested this week and came in just shy of 200 bushels per acre (bpa). While the season was dry, there were little-to-no problems with heat during pollination or any significant insect or disease pressure. And Mike noted that in this area of the country, yield tends to be reflected in soil types.

"We have some pretty good soil types on this farm for dealing with dry conditions," Mike said. "The majority of our sandier soils are irrigated, but in corners or other areas where they aren't, we will have some tough spots this year where yields drop to 50 bpa or so." Other areas of the Red River Valley have deep, dark clays that are amazingly productive under typical rainfall scenarios, but struggle in drought.

The Langseths had just begun to nose into some irrigated acres this week but were optimistic about the yields they would find there.

Meanwhile with soybean harvest complete, Chandra has been busy collecting soil samples. Included in that was the sample for HG type testing, which requires a full gallon of soil to conduct the test.

Back in 2003, Mike's father, Paul, was serving on an agricultural advisory board that alerted him to the yield penalty of SCN. "We got super aggressive about planting SCN-resistant varieties from the beginning," Mike recalled. Their first varieties contained Peking resistance, but the varieties weren't particularly good on other problems common to the area, such as iron deficiency chlorosis (IDC).

"But by getting aggressive and always planting cyst-resistant varieties we've kept our (egg) numbers low. That doesn't mean we don't have them (SCN), or they don't show up when we test. But testing usually assures us they are at low enough levels. I give Dad credit for starting that program and staying proactive," he added. Today, PI 88788 resistance is the predominant source of resistance in this maturity zone. The Langseths also now grow soybean for seed, which can further limit their ability to switch up varieties.

Chandra opted to test the field where SCN was first discovered on the farm and the one that routinely carries the highest SCN egg counts. "I kind of have my hands over my eyes wondering what this HG test will find, but I also picked the worst field we have because I want to know the worst-case scenario," she said.


Although Grossman routinely soil tests to dial in fertility, he's never soil tested for SCN. Rotation to a non-host crops, resistant varieties and seed treatments have been his answer to managing for the pest.

"We've never experienced what we thought was a yield drag," he said. "So, right or wrong -- we've just never tested." He's not alone. A 2020 DTN online poll answered by 273 respondents found only 27% had ever scouted or soil tested for SCN; 40% had never tested and 32% had tested, but it had been more than three years.

This should be an excellent year to start testing. The SCN lifecycle speeds up during drought-like conditions and Grossman contended with plenty of drought this year. (See "Time to Manage SCN Through Fall Soil Tests,"…)

Like the Langseths, Grossman selected his most suspicious field for the HG type testing. "I can't say we saw any obvious symptoms in that field. What we noticed is that patch has been acting different," he said. "Other beans near it were growing like gangbusters this year, while this field just kind of limped along."

It is a small field (about 5 acres) and in a corn-soy rotation that is soil tested every other year. "I know the pH and fertility -- or what I like to call the foundations -- are right. It will be interesting to see if the SCN testing unlocks some answers." Nematodes feed on the plant's vascular system, which can make it vulnerable to other secondary infections, but symptoms aren't always visible above ground.

Harvest is winding to a close for the farm and Grossman gives a lot of the credit to his father, Curt, and brother, Trent, for pushing ahead. The area received 4.25 inches of rain last week, delaying harvest for several days. When temperatures plummeted below freezing early this week, soils firmed up enough so they could head to the field in the wee hours of the morning to shell corn.

Baranick said the Tina, Missouri, area should remain dry in the coming week. "Temperatures will be warm to start off the week but should drop later in the week with a somewhat stronger front moving through," he said.

On Nov. 2, Grossman said they still had 150 acres of corn and 40 acres of double-crop soybeans to harvest. They also plan to tackle a few custom harvest jobs, but the end is in sight.

This week they shelled a field that Grossman has been watching all season. It is what he considers their best "hill dirt" farm and had the least amount of rainfall of any of their acreage this year. "To see that field averaging 160 bushels (per acre) given those soils and limited rainfall is pretty incredible," he said.

As winter closes in, Grossman's thoughts begin to turn to cattle. This week he moved some hot wire to give cows access to cornstalks.

He's also trying something new this year by supplementing mama cows with liquid feed. "This product is really good about controlling consumption," he said. Grossman was a feed salesman for five years before juggling farming with a job as a loan officer at a local bank.

"There was a lot of CRP hay put up this year and I had to do some myself. It is clean grass, but my fear is some of it isn't going to be as nutritious as what comes off fertilized hay ground," he said.

Old school cowboys prefer to hand feed dry feed every day. "I've always been hard-headed that way too," he admitted. "And I do like to call them up to feed and count during the 60-to-70-day calving span. But this liquid option is fitting my schedule right now."

Want more information on SCN management and testing? Go to The SCN Coalition…

For information on losses from SCN in the U.S. and Canada go to:…

Learn more about HG type testing from the University of Missouri here:…

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Pamela Smith

Pamela Smith
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