Volunteer corn, is it only cosmetic?
By: Justin Hunter | Agronomy Sales
Surely, most farmers might cringe at the sight of volunteer corn in their soybean fields, but they may not think of it as impacting their bottom line. The problem of volunteer corn can
be looked at from two different angles: weed and insect management. Let us explore both topics and unpack the economics behind them.
According to research conducted by South Dakota State University, the University of Minnesota, and University of Nebraska-Lincoln, volunteer corn ranging from 800-13,000 plants per acre has the potential to cause up to a 54% yield loss in soybeans. One can determine how many volunteer corn plants per acre by measuring 1/1000th of an acre (17’ 5” for 30” rows and 34’ 10” for 15” rows), counting the number of plants within that measurement and multiplying that number by 1,000. Taking measurements in multiple, randomized locations throughout a field to get an average is ideal. Finding at least one plant per measurement, on average, will classify a soybean field as having significant yield loss potential.
The economic impact of volunteer corn from a weed management perspective is staggering. Even if one considers 54% yield loss as the worst-case scenario, taking only one-third of the worst-case scenario with a typical 60 bu/ac and $10/bu selling price for soybeans would cause a $108/ac loss. Luckily, the control option is far less costly, especially if one is using a volunteer corn-killing herbicide, such as Clethodim, in their post-spray pass.
In addition to the yield influence of volunteer corn pressure in soybeans, it also brings about the challenge of managing corn rootworm (CRW) the following year. This challenge is harder to calculate in terms of $/ac, but it is by no means a lesser threat. With the rise of “extended diapause” in the northern CWR species (where these insects have adapted to the 2-year, corn-soybean rotation by delaying egg hatching during the soybean year) farmers need to monitor volunteer corn more closely. Many of the hybrids planted on rotated corn acres do not have adequate below ground traits for CWR protection, but being proactive and adding a SmartStax, Qrome, or Agrisure Duracade trait would be recommended if volunteer corn is a reoccurring issue. Looking at the cost of seed alone, going from a VT Double Pro (no CRW protection) to a SmartStax (CRW protection) will cost anywhere from $12-20/ac, but avoiding taking any action at all has the potential to become much more costly.
The amount of volunteer corn in a field plays a large role in determining whether it is “only cosmetic” or if action needs to be taken. However, it is safe to say that no volunteer corn is always better than some volunteer corn. Even if the pressure is not large enough to be impacting yield, it still may be harboring insects that can negatively affect future corn crops.
Bayer. (2020, May 26). Northern corn rootworm and extended diapause. Specialty Hybrids™. https://www.specialtyhybrids.com/en-us/agronomy-library/northern-corn-rootworm-extended-diapause.html
DiFonzo, C. (Ed.). (2022, March). The handy BT trait table for U.S. corn production. Texas A&M AgriLife Research and Extension Center at Lubbock. https://agrilife.org/lubbock/files/2022/02/BtTraitTable-March2022.pdf
Jha, P., Hartzler, B., & Anderson, M. (2020, September 3). Management of volunteer corn in fields affected from derecho. Iowa State University Extension and Outreach | Integrated Pest Management. https://crops.extension.iastate.edu/blog/bob-hartzler-meaghan-anderson-prashant-jha/management-volunteer-corn-fields-affected-derecho