Volunteer corn can cause a number of issues in a corn and soybean rotation and, most importantly, can cause potential yield loss. When kernels or ears from your combine are dropped during corn harvest, they will overwinter in your field, then germinate in the spring and ultimately compete with your newly planted crop.
That’s why management of volunteer corn is critical to any operation and why volunteer corn is considered a weed.
Why is volunteer corn a problem?
Volunteer corn is a problem because it competes with crops for moisture, nutrients and light. The glyphosate-tolerant gene contained in most corn and soybeans is passed on to the grain produced, making it glyphosate tolerant as well. This makes continuous corn production difficult in high volunteer corn situations where there is no selective herbicide to use to accomplish killing volunteer corn without killing the corn crop also being grown. In some cases, tillage may be the best and only solution.
If volunteer corn is left in soybeans, rootworm beetles can be attracted to the volunteer corn and lay eggs in the soil, eliminating the value of rotation control of corn rootworm the following year. Diseases can develop in volunteer corn, producing more disease inoculum (the individual part of the pathogen that actually causes disease within the host), resulting in greater disease pressure the following year when a new corn crop is planted.
Volunteer corn can negatively impact your crop through:
- Insect damage. First generation European Corn Borer (ECB) feed inside stalks and may cause stalk breakage at or before harvest. Second generation ECB feed on ear shanks that may cause ear droppage from the stalk before harvested. Rootworms feeding on roots will cause corn plants to lodge (when the corn stalk breaks or is displaced), making harvest difficult and causing possible ear loss.
- Disease presence. Diseases within the corn field can cause plants to die prematurely as well as stalk lodging, leading to corn ear losses.
- Grain loss from your equipment. During harvest, your combine may need adjustments to minimize the loss of corn grain.
- Corn variety selection. Some hybrids have poor standability with below average ear retention.
- Wind and hail damage. Both can have a negative impact by causing ear loss as well as grain loss (kernels left behind) in the field.
- Poorly timed tillage. Spreading the corn loss in the ground with tillage can actually spread the lost grain. Unless tillage is done in the fall when the lost grain may germinate before freezing, no-till is best practice where grain loss is evident.
Methods to avoid volunteer corn problems:
- Corn hybrid selection. Select a good disease resistance package with hybrids that contain traits for rootworm control on continuous corn fields, or use an in-furrow insecticide at planting. Select hybrids with traits that offer ECB control and with good standability and ear retention.
- Fungicide application. Scout fields for disease presence and apply fungicide when needed to maintain plant health until maturity.
- Monitor harvest equipment. Monitor your combine closely and adjust where needed to avoid grain loss in the field.
- Timely harvest. Harvest before wind and moisture reduce stalk integrity and lodge corn plants, and when proper moisture content can help to prevent grain shattering in the combine.
- Well-timed tillage. Avoid tillage that will spread the grain lost and instead consider tillage in the fall, if part of your operational practices.
What can be done about volunteer corn
In soybean production, there are several chemistries that can be applied to kill volunteer corn, even though it is glyphosate tolerant, such as foliar grass control products like clethodim, for example.
By treating volunteer corn in soybeans early, you can reduce plant competition for fertilizer, water and sunlight, and possibly allow for lower rates of herbicides to be used. Rates change according to the size and stage of volunteer corn to be controlled. By waiting to treat later, you may have given up yield that cannot be recovered.
When selecting products to control volunteer corn, always read and follow label use directions. Adjuvants are an important ingredient when controlling volunteer corn and vary among the products being used.