Ohio State University Plant Pathologist Dr. Anne Dorrance says some soybean growers are beginning to see stunting and uneven growth in their fields - and that could be a sign of Soybean Cyst Nematode. She says that means it's time for growers to get in their fields, dig up plants, and take a look at the roots.
"When growers first pull up the plants they'll find the larger nodules, which are a little bit smaller than an eraser on a pencil," Dorrance said. "But the pearls are the teeny, tiny beads that are on the roots indicative of the cyst female feeding."
Even if a grower doesn't see these signs of SCN, Dorrance emphasizes the importance of in-season scouting. She notes SCN can cause substantial yield loss without causing symptoms and getting into the field to scout will allow growers to see if their resistance package is working. Dorrance says the next step is getting a cyst count.
"We really want growers to test the fall after soybeans because that's when the population numbers will be the highest," Dorrance said. "Based on that count you begin looking at management plans. If it's really high you know you have to rotate out of soybeans and begin getting that field ready for wheat, alfalfa, or corn or whatever the other crop is in your area."
Unfortunately, Dorrance says SCN soil sample results are notoriously variable. She's been participating in a multi-state SCN study and cites a field where they found from zero all the way up to 5,000 eggs per half-a-cup of soil. As a result Dorrance says it's vital for growers to get a good sample.
"If they are getting a good sample, you know a lot of different cores and it was well mixed, then they can have a higher degree of confidence," Dorrance said. "If they took a few cores here and there, kind of short shirted it, they're probably not going to be able to have as much confidence about that score when they go and get their soil test."
One other key finding of this multi-state research is that some nematode populations are beginning to adapt to resistant varieties. They found one type that can reproduce on the 88788 soybean variety. She says the adaptation to this source of resistance will be slow, but at the same time she says growers need to be aware that the resistance isn't always going to work.