Digging For SCN When You Scout Your Soybean Fields
While you’re scouting for insects and diseases in your soybeans this summer, you’ll want to bring a shovel along to scout for soybean cyst nematodes (SCN).
Nematodes are usually invisible to the naked eye. However, SCN females swell during the growing season—making them visible. Dr. Greg Tylka, nematologist with the SCN Coalition, says it’s important to know what you’re looking for in the root system.
“On healthy soybean roots, there’s little bumps called nitrogen-fixing nodules, and sometimes they could be confused with SCN females,” he said. “Nodules are going to be the color of the roots because they’re made out of tissue. SCN females are going to be white.”
Tylka says there’s also a big size difference as well.
“The females are about the size of a period at the end of a sentence,” he said. “You almost can’t see nitrogen nodules when they’re that small—the ones you see are going to be larger.
The life cycle of SCN is pretty quick—four weeks from egg to death. It starts life entering the soybean’s root system and consuming the vascular system. After two to three weeks, it will either become an adult male, which will return to the soil, or an adult female and continue to feed.
“[Females] pop out of the root, or they’re on the surface of the root,” he said. “Their head is still attached to the vascular tissue, but most of their body is outside the root. The males will fertilize the females, and the female will make 50 to 100 eggs outside of her body, but she fills internally with another 200 to 250 eggs. Once she dies, her body changes colors, and that dark brown, swollen dead female full of eggs is called the cyst.”
Those eggs will hatch and start the cycle all over again. Even though growers can lose as much as 14 bushels an acre, Tylka reminds growers that it’s not a death sentence for soybean production.
“It’s like high blood pressure in humans—it’s a serious health problem for soybeans and it’s chronic because it’s not ever going to go away,” he said. “But the best thing a farmer could do is figure out what fields have SCN and start managing it with resistance like nonhost crops and seed treatments.”
After harvest, Tylka encourages farmers to take soil samples and send them to the lab. For more information on where to take your samples, visit TheSCNCoalition.com.