Editor’s note: The following was written by Dave Nicolai, Liz Stahl and Jeff Gunsolus with the University of Minnesota for its Minnesota Crop News website.
Excessive precipitation in some areas and dry conditions in others, along with wind storms and tornadoes, has taken its toll on consistency in corn yields. The weather, along with disease and the early dying of some corn hybrids, has led to limited stalk strength at harvest.
As a result, we expect the occurrence of volunteer corn to be greater in areas of the state in 2019 due to a higher potential for corn ears and kernels to be left in the field this fall.
Volunteer corn has the potential to reduce crop yield as well as impact the long-term management of corn rootworm (CRW).
Volunteer corn can significantly reduce soybean and corn yield, although research shows volunteer corn is less competitive in corn than in soybean. For example, volunteer corn populations ranging from 800 to 13,000 plants per acre resulted in yield losses of 0 to 54 percent in soybean and 0 to 13 percent in corn, according to South Dakota State University research.
In University of Minnesota trials, volunteer corn populations had to reach at least 8,000 plants/acre before yield was reduced an average of 8 percent.
Most of the hybrid corn planted today carries traits for resistance to insects such as CRW. Crop rotation is one tool to help manage CRW, but any benefit is essentially nullified if a heavy population of volunteer corn is present in soybean.
CRW larvae are able to feed and mature on uncontrolled volunteer corn. Also, late-pollinating volunteer corn is very attractive as a feeding and egg-laying site for CRW beetles, creating the potential for CRW problems the following year.
Volunteer plants of Bt-CRW hybrids will also express the Bt toxin at variable and reduced levels. Exposure of CRW larvae to sub-lethal doses of the Bt toxin has the potential to hasten development of resistance to Bt-CRW traits.
Selective use of fall tillage can affect the amount of volunteer corn next year.
Following harvest, if a grower has a field where lodging, ear drop or shelling at the head were significant, adjusting the fall tillage strategy can help mitigate volunteer corn the following season. Allowing seed to stay on the soil surface may reduce populations the following season by allowing germination in the fall prior to freezing temperatures.
Seed left on the surface is also much more susceptible to predation or decay.
No-till extends the benefit of no fall tillage. By not incorporating seed into the soil, it is left on the soil surface where it is much less likely to result in successful germination and emergence.