Volunteer soybeans impact corn yields this season
Move over waterhemp, ragweed, lambsquarters and all your weedy friends. There’s a new rabble-rouser in cornfields this season: volunteer soybeans.
Nebraska farmer Tim Gregerson says volunteer soybean populations have been on the uptick in recent years in his area. The 2012 drought gave them a huge boost, catapulting populations to levels this season that are likely to affect some farmers’ corn yields.
"We had a tremendous amount of shatter loss last fall before we could get the soybeans combined. That’s what contributed to such a big problem this summer," says Gregerson, who farms near Herman, Neb.
Volunteer beans are a hidden weed; you can’t see them from the road
He adds that the situation, which started with soybean shatter, was then complicated by cold, dry winter conditions. Those conditions helped rogue soybean seed retain its viability in the field until this spring, creating the perfect storm for growth.
"It seemed like we went straight from winter right into planting, and the beans came up with the corn," Gregerson says.
Yield risk. Volunteer soybeans are usually not very competitive with corn, explains Amit Jhala, an agronomist and associate professor at University of Nebraska–Lincoln Extension. But Jhala says that he has seen some volunteer soybean populations this year in Nebraska cornfields that he expects will impact yields. Extension agronomists in Minnesota and South Dakota also report that farmers in their respective states have identified volunteer soybean problems this season.
In addition, during the Pro Farmer Midwest Crop Tour this past August, Chip Flory, Pro Farmer publisher and editor, notes that he saw "way too many" volunteer soybeans growing in the fields that he walked.
"These beans are a hidden weed; you can’t see them from the road, and they’re a harbor for soybean diseases and other pests to hide on for a year before the bean crop comes back the next year," he says. "There’s no denying that a healthy stand of beans in a corn field is draining nutrients and moisture this year’s corn crop needs to build a big yield."
Gregerson says he was able to apply postemergence herbicides and got good control of volunteer soybeans in his corn, but he is concerned some farmers weren’t as fortunate. In those cases, he worries there will be a surge in soybean cyst nematode populations next spring.
"If you let volunteer soybeans go in your corn, then you don’t break the cyst nematode reproductive cycle because the corn acts as a host," Gregerson explains. "The nematode will lay eggs in your corn, and that will set up another problem for next year."
Unfortunately, agronomists say there is no effective weed-control measure that farmers can take at this late date to address volunteer soybeans in corn, much like other weeds this time of year.
Agronomists recommend that farmers identify problem areas in fields as they combine corn this harvest so they can be prepared to address any resurgence of volunteer soybeans in fields next spring.
Early Measures Work Best
If volunteer soybeans show up in your corn next season, consider these control measures from Darrell Deneke, South Dakota State University (SDSU) Extension IPM coordinator.
He says soybean size at the time of herbicide application will determine the degree of control you get. As is true for most weeds, smaller volunteer soybeans are easier to control than larger ones. Try to get on top of any problem before volunteer soybeans exceed the V3 growth stage.
Using 2,4-D to control volunteer soybeans is one option, he says, although SDSU research shows that soybeans are not as sensitive to 2,4-D as they are to other plant-growth regulator herbicides, such as dicamba or clopyralid. Plant-growth regulator herbicides, such as Hornet, that contain clopyralid should provide effective control to smaller soybeans, he says. Products that contain dicamba, such as Status, Distinct and numerous generics, will provide effective control over a wider range of volunteer soybean growth stages. As always, read all product labels for application directions and ensure the herbicide you plan to spray is labeled for use in your state.
You can e-mail Rhonda Brooks at firstname.lastname@example.org.