Something to talk about: SCN is leading cause of soybean yield loss

DURHAM, N.C. — What would you do if you had $330,000 to spend on anything you wanted?

Would you buy a small implement? Put up a building? Send your kids to college?

Get a new boat or a new truck?

Maybe even buy some more farmland?

Well, that is the amount of money his family’s medium-sized farm in southwest Iowa has lost to soybean cyst nematodes over the last 10 years, said Scott Kay, vice president of U.S. agricultural solutions at BASF.

“It’s real money, right? We’re not talking about something that’s not substantial,” he said, recalling a conversation with his father and son and an agronomist in a field as they counted the cyst nematodes on the soybean plants and calculated their yield impact.

Growers’ goal to get to 100 bushels an acre is in jeopardy, Kay warned.

“If we don’t get this under control, we’re not going to make it,” he said. “That’s going to be the difference between making money and not making money.”

However, no one is talking about SCN, Kay lamented.

“It’s probably one of the least talked about topics,” he said. “It’s an industry problem that we don’t talk about it. One, we don’t personalize it. We don’t equate what it would have been worth.”

So, why is it not discussed? The answer is simple, Kay said.

“The seed and crop protection industry is not going to talk about it a lot if they don’t have a solution,” he answered.

It is now estimated that SCN, first discovered in the United States in North Carolina in 1954, costs soybean producers close to $1.5 billion per year.

A ‘Nightmare’

SCN has been the No. 1 pathogen threatening soybean production in North America since the 1990s, said Horacio Lopez-Nicora, assistant professor of soybean pathology and nematology at The Ohio State University.

Added together, he said, the next five pathogens — white mold, sudden death syndrome, Phytophthora root and stem rot, root knot nematode and charcoal rot — do not reach the damage that SCN can do.

“It’s an animal like you and me. It’s an animal that will overwinter as an egg, it will lay eggs and it will stay in the soil,” Lopez-Nicora said. “And as a soilborne pathogen, once you have it in your field, you will not get rid of it. You will have to manage it.”

Symptoms of SCN include short and stunted plants, yellowing and chlorosis and nutrient deficiency. But those symptoms are not always visible.

“The grower may not actually realize the effect of the nematode,” Lopez-Nicora said. “This is the nightmare in the Midwest — the nematode has adopted so well to our soybean operation that we do not see a visible symptom and yet we’re losing 30% of yield.”

The SCN Coalition encourages farmers to scout for SCN, by digging — not pulling — roots and looking for females or by collecting soil samples for testing.

“Roots don’t lie,” Lopez-Nicora said.

Collect 15 to 20 one-inch-diameter core samples, eight inches deep, for every 20 acres. Mix the cores well, put the mixed soil into a soil sample bag and send it to a SCN testing lab.

Lopez-Nicora shared three approaches to collecting soil samples: collect soil cores using a zigzag pattern, collect soil cores from logical areas or management zone in the field, or collect soil cores from high-risk areas in the field where SCN might first be discovered.

To see how much SCN is costing you, use the SCN Profit Checker at: www.thescncoalition.com/profitchecker.

Rotate, Rotate, Rotate

To manage SCN, follow the three Rs, developed in 2005 by Terry Niblack at OSU, said Lopez-Nicora.

“Rotate, rotate, rotate,” he said. “Let’s not feed this animal with the same genetics, right?”

• Rotate crops.

• Rotate resistant soybean varieties.

• Rotate sources of SCN resistant genes.

“The first rotate is we’re going to rotate crop. Get out of soybean. It’s a soybean cyst nematode for crying out loud,” Lopez-Nicora said.

“So, if we grow corn, it will not reproduce. It will infect the roots, though. But it will not reproduce.”

Rotating resistant soybean varieties is complicated, however, since more than 90% of the commercially available seed has the same PI 8878 source — and, after about 30 years, that is no longer as effective, especially in the Midwest.

“Unfortunately, soybean cyst nematode continues to adapt and reproduce on PI 8878,” Lopez-Nicora said.

“Unfortunately, the population that we have now was not meant to be used with that source of resistance. If we go back 30 years ago and we tested those same varieties with HG Type 0, the label was very accurate. Unfortunately, we are not there anymore.”

Today, he said, soybean growers need to rethink their management strategy.

“We need to protect and enhance the root health; consider a nematode-protectant seed treatment; use a cover crop, to enhance soil health, but also use it as a trap for nematodes, reducing the population,” he said.

Lopez-Nicora acknowledged the difficulty of this challenge.

“We are just running so fast and doing so much to just keep in the same place,” he said.

Perception vs. Reality

Almost all farmers are aware of the problem with SCN, but few recognize the severity in their own fields.

Caroline Currie, BASF North American strategic marketing lead for seeds and traits, reviewed market research conducted at BASF.

She said SCN concerns are lower on the priority list. Only about one-third of growers say SCN is among their top three challenges, she said, behind weed pressure and weed resistance, disease pressure and resistance, and insect pressure and resistance.

“Perhaps could this be because these are problems or challenges that are quite visible, easy to see above ground, easy to detect, and there are tools to do something about it?” she said.

Only 30% of growers reported pressure from SCN, Currie said.

“‘This is somebody else’s problem. This is not on my farm,’” she opined. “‘It is an issue, but it’s on someone else’s farm.’”

Farmers perceive only 14.4% of soybean acres are impacted by SCN today. They expect this to increase during the next decade, but only marginally.

Most said they have “low” pressure, losing 2 bushels an acre and in 49% of their fields.

“We have some real opportunity here to start educating,” Currie said.

She then detailed an expansive dataset that sampled more than 6,000 fields.

“We saw some pretty alarming egg counts that would characterize a different reality,” she said.

In that sampling data, SCN was detected in over 90% of fields — and in 58% of the sampled fields it was at damaging levels.

“So, you basically see anywhere where you grow soybeans, you have SCN,” said Mike McCarville, trait development manager at BASF. “And it continues to expand.”

McCarville equated the loss from SCN to one out of every 10 soybean crops.

“Nine crops go to your family and to people to feed them,” he said. “One is feeding nematodes. This is the herd of cattle that they don’t realize they’re raising, and it’s really expensive to raise.”