It is now time to start scouting for the number one cause of yield loss in soybeans, the soybean cyst nematode (SCN).
The SCN Coalition encourages growers to check for soybean cyst nematode females, which can be found on soybean root systems. Greg Tylka, SCN Coalition co-founder, notes: Now is “one of the rare times you can see the female with the naked eye.”
“If they’re going to become a male, they’ll stop feeding and change back into a worm-shape. If they’re a female, they continue to feed and take on this lemon-shape. The females eventually get so large that they pop out of the root and you can see them on the surface of the root. At that point, the worms – the males in the soil – mate with the females on the roots. And the little lemon-shaped females we can see with our naked eye produce about 50 to 100 eggs outside their body and fill up internally with another 200 to 250 eggs,” Tylka said.
Growers should begin scouting for the white females in late July and early August. Tylka adds, “Scouting is the start of managing SCN.”
“(Scouting) tells farmers and agronomists SCN is present,” Tylka said. “For fields that are going to have soybeans in 2021 or the next time soybeans are grown in the field they have soybeans in this year, pull soil samples in the fall. That consists of soil cores; twenty or so cores for every twenty acres. Put all those cores in a bucket, mix them up well, put them in a bag, and send them to a lab that processes SCN samples.”
Growers can send soil samples to Iowa State University’s Plant and Insect Diagnostic Clinic or private laboratories. As farmers gain a better understanding of their SCN populations, they can weigh management options such as resistant varieties, non-host crops, and seed treatment. Tylka says, “Farmers need to remember, soybean cyst nematode is not a death sentence.”
“It’s not a death sentence for your soybean crop; it’s something to manage. It’s a lot like high blood pressure in humans; it’s a chronic health problem. You’re better off knowing you have the problem and managing it with a multiple management strategy than ignoring it and hoping it goes away or doesn’t become too damaging,” Tylka said.