Digging for answers on costly nematodes

DURHAM, N.C. — After introducing the Nemasphere nematode resistance trait, the most groundbreaking innovation in soybean cyst nematode management in over 60 years, experts were questioned by Bryan Perry, the U.S. head of seeds and traits for BASF Agricultural Solutions.

SCN is the leading cause of soybean yield loss in the United States, costing growers an estimated $1.5 billion in yield annually.

The panel consisted of Horacio Lopez-Nicora, assistant professor of soybean pathology and nematology at The Ohio State University; Mike McCarville, trait development manager at BASF; and Julia Daum, BASF senior program leader.

Nemasphere produces a novel Cry14 protein that is ingested by nematodes, interfering with nutrient uptake in their intestines and leading to the nematodes’ death.

Stacked with the Enlist E3 herbicide tolerance trait, it is anticipated to be available in 2028, pending regulatory approval.

Why do you feel there is such a gap between perception and reality when it comes to what soybean growers believe and what they know about SCN?

Lopez-Nicora: The lack of symptomology, something that cries out loud that I’m sick. In 2016, we did a survey in Ohio where besides collecting samples and reporting the numbers that came back, more than 65% positive for SCN, which pretty much aligned with what BASF is seeing, one of the questions was, before they received the results, do you know you have SCN or do you suspect that you have SCN?

More than 75% of the growers replied, “I don’t have SCN” or “I don’t know if I have SCN” — and this is that portion that the results went back positive. So, they were very confident that they didn’t have SCN when the results were positive and, in most cases, above the damage threshold.

Some of the answers that really surprised me is, “I don’t want to know.” And maybe that can be linked to how important of a pathogen it is. It’s opening a can of worms, literally.

Mother Nature has continued to evolve. From a stewardship maintenance standpoint, what do we need to do to protect this technology?

McCarville: Bt technologies can have a couple different paths. European corn borer Bts have been extremely durable, probably the No. 1 success story in pest management, for sure. And then the alternative of that, corn rootworm Bts, right?

So, with this technology, we have to be very unique about it. You can’t approach it like an insect technology.

With the other Bts, you’re going to go high dose in refuge. You get really high efficacy and then plant some susceptible beans and look out for some crossing.

SCN does not randomly mate. If you look at the genetics of it, it’s basically half sib matings, which means that we need to take a very different approach, which is why we submitted our registration to the EPA and they approved our resistance management plan.

So, they’re behind it — which is that we are going to stack this with native resistance, putting two barriers side by side together and keeping those side by side the entire time.

You’re never going to see a Nemasphere traited line out there that doesn’t have a native trait. So, we’re going to keep two separate, unique modes of action together in the field.

And if you do the resistance management modeling on it, that is essentially the most durable way to manage cyst nematode. The other options don’t really fly because you can’t do a refuge if it’s not going to randomly mate.

So, the best way to do it is to get two unique modes of action, put them together and always make sure that they’re together.

What drove the BASF team to have that forward-thinking vision of, wow, we think there’s going to be a problem with SCN in the future, long before growers were even seeing a problem in their fields?

Daum: When you start seeing a resistance, you know there’s a history in that, right? Once you see some happening, you know it’s not going to get better; it’s going to get worse. So, you could predict that something is going to be needed to gap stop, right?

And as it turned out, as we developed this trait, the problem just got worse. So, it was just clear that we were on the right track.

Do you see it shifting in the south? When does SCN become a southern problem, or does it even become a southern problem?

Lopez-Nicora: SCN is very important in the Midwest. It costs significant yield reduction. But when we get together with our other colleagues from the southern states — to mention some, Travis Faske in Arkansas and Tristan Watson in Louisiana — they’re experiencing more challenges with other plant parasitic nematodes, such as root knot nematode, lesion nematode, reniform, and less with soybean cyst nematode.

The expansion of soybean is migrating towards South and North Dakota. Those should be areas of high risk that we need to focus specifically for this pathogen.

Bt has been around in corn for a while. Why has it taken so long to bring a Bt trait in soybeans to the market?

Daum: There are Cry proteins in soybeans, just not nematode Cry proteins. I can’t tell you all the tricks, you know, but when you use the methods that they used to put the insecticidal Cry proteins into soybean, they didn’t work. You didn’t get a soybean plant that expressed in the soybean without doing something either bad to the soybean or just not expressing it at all.

So, we started doing things that not everyone was doing, to try to test the waters on, well, maybe if we try this, it’s not supposed to work, but everything that was supposed to work didn’t. That’s where you reach into your bag and you pull out a new approach.