Burcucumber can be one of the most difficult weeds to manage in corn. It can emerge well into the growing season and its vines can spread up to 25 feet and twine around corn plants.
"It can drag down the corn and make it difficult to harvest, impacting yields," said Mark Loux, weed scientist for the Ohio Agricultural Research and Development Center.
Loux is in the middle of a two-year study to determine the most effective way to manage burcucumber in corn.
"While we previously had an idea of the relative effectiveness of various pre- and post-emergent herbicides, we weren't sure what would be the most effective combinations of herbicides and application timings to provide the most consistently effective late-season control," said Loux, who is also a weed science specialist for Ohio State University Extension. "Late-season emergence varies from year to year based on rainfall patterns and other factors, but when burcucumber emerges in big numbers after post-emergent herbicides have been applied, it can create a mess."
Loux's research compares the effectiveness of various residual pre- and post-emergent herbicides and the timing of their application. In 2010, the first year of the study, researchers applied herbicides Lexar, Corvus+atrazine and Harness Xtra at planting (pre-emergent) and early post-emergent, when corn was at the V2 (second-leaf) stage. These treatments were followed with various residual and non-residual post-emergent herbicides, including Callisto, Spirit and bromoxynil. Researchers tested different timings for the post-emergent herbicides and single and multiple applications.
One of the research sites in 2010 was non-GMO corn; several more are planned in 2011, including at least one with glyphosate-resistant corn, Loux said.
The study's 2010 findings included these observations:
* The Lexar and Corvus+atrazine were much more effective than the Harness Xtra for control of burcucumber between planting and the post-emergent application. Not only were there fewer burcucumber plants with the Lexar and Corvus+atrazine, but the weeds were small and had not started to vine at the time of the post application. Plants in the Harness Xtra treatments were much larger, and some had already extended tendrils to the corn plants by the time the post-emergent herbicides were applied.
* There appeared to be more effective control when the residual herbicides were applied at the early post-emergent stage instead of at planting, but this was much less important than the choice of residual herbicide. These results indicate that delaying the residual herbicide application until corn is at about the V2 stage could provide more effective control in mid-season and allow a more flexible application window for later treatment.