As Extension personnel predicted, reports of cyst nematodes have spread beyond the borders of Arkansas' Prairie County. But several weeks ago, at the outset of the problem, Brent Griffin was called to this Des Arc soybean field (“hot spots” abound up and down the rows) because the producer thought he had a problem with salt.
“That wasn't the case. I pulled a couple of plants and could just eyeball the cyst nematodes,” says Griffin, Prairie County Extension agent. “My heart did a flip and I thought, ‘Uh-oh, this isn't good at all.’”
At this time, a few soybean varieties have resistance to some races of nematodes. But for some races there are no resistant varieties at all.
“Some of these nematodes are hitching a free ride on our beans,” says Hank Cheney, also an Extension agent in the centrally-located Arkansas county. “If there's one thing we need breeders to be working on, it's resistance. The push for higher yields — and that's a problem seed companies face with demand from producers — has left resistance in the background. We need to get nematode resistance back towards the front of the line.”
Twenty-five years ago, seeing nematode damage was common. In response, breeders gave producers varieties resistant to races 3 and 14, says Cheney. “After that, it's like the problem receded. We let our guard down and assumed the things had been taken care of. Well, what actually happened was the nematodes just shifted races on us. Now, we have these new races with no resistance. I hope it isn't the case, but we could be looking down the barrel of a big gun.”
A couple of years ago, the men started picking nematodes up in the southern end of the county. Primarily, Prairie County is in a rice/soybean rotation. Both Griffin and Cheney say after a season of rice, nematode severity in a field is a bit worse.
“Behind beans, they're plenty bad,” says Griffin. “But behind rice, for some reason, they're worse. We've always been told rice is a good rotation crop because it will drive nematodes deeper into the soil. But what we're seeing here seems to be the exact opposite of that.”
As a response, producers in the county are shifting more acres into grain sorghum and corn. Much of the shift is attributed to nematodes, much to weeds and red rice.
“I just wish we could have a company close by that would take grain sorghum,” says Cheney. “We don't have as much on-farm grain storage as other counties. That coupled with no local facility to deliver the crop to has hindered milo production here.”
Up until Griffin found nematodes in this soybean field a couple of weeks ago, it looked like Prairie County would pull in a decent soybean crop. Despite all the rain (this field got 11 to 13 inches of rain during June alone), optimism abounded. While a good crop is still possible, Cheney says he increasingly fears for the producers he serves.
“The next thing that can happen is root disease. Charcoal rot, SDS and other things can give these fields a double helping of bad news. Many farmers are going out and surveying their soybeans, setting up their irrigation systems. They're noticing stunted beans all over the place. I got calls yesterday on just that,” he says.
And it makes the men wonder.
“In the past, I've been told that soybean fields looked good, were watered and managed correctly, and the yields were still bad,” says Cheney. “Now, it makes me wonder if maybe nematodes might have been causing a yield drag.
“2001 is when they showed up strong, but they had to have been there at some level right along. I can't shake the thought that maybe nematodes have been picking us apart and we didn't know it.”
Griffin calls us over. Having just pulled a soybean plant and shaken off the dirt, he's now knifing its taproot.
“Here, look at this: you can see nematodes on these roots. And look at the deadening end of the taproot. That's charcoal rot. These beans, when they do try to grow, will choke off and die.”
Before moving on to the next nematode-affected field, Griffin makes another prediction: “I'm guessing this producer will go with grain sorghum next year.”