The classic definition of a weed is a plant out of place. That means that even though corn is one of the staple crops in the U.S., and forms the backbone of the emblem of the FFA, because corn is grown across the country, it's a weed in a soybean field, or even in a cornfield if it's growing back from last year.
"It makes a big plant and it can cause a lot more yield loss in soybeans than many people think," advises Barry Fisher, state agronomist for the Natural Resources Conservation Service. "The other thing it can do is mess up the value of rotating crops.
"In areas where a farmer can go from corn to soybeans and still doesn't need to apply an insecticide for rootworm control, if there's enough volunteer corn and it attracts rootworms, you can lose the effect of having the field in a different crop for that year. Then the next year when you go back to corn you would need to apply a soil insecticide of use Bt rootworm corn even though the field was in a crop of soybeans in the preceding year.
Of course, in certain parts of the state, particularly northwest Indiana but in much of northern Indiana as a whole, the rootworm variant that can lay egg sin soybeans means that you no longer enjoy the benefits of the crop rotation form corn to soybeans helping on rootworm control anyway. In that case, either a soil insecticide or Bt-rootworm corn would be needed following soybeans anyway.
Volunteer corn is becoming more of an issue if it's herbicide resistant, such as Roundup ready or Liberty Link. In soybeans, it's still not overly difficult. Several good grass herbicides will still take down even glyphosate resistant volunteer corn in soybeans. It's in corn after corn where volunteer corn becomes more of an issue. There are no good options.
"One solution is to go no-till," says Don Biehle, superintendent of the Southeast Purdue Ag Center near Butlerville, and a veteran no-tiller. "You don't bring up corn and cover it, so just laying on top it's less likely to germinate. You may get some, but not nearly as much.
The volunteer corn problem could be worse in parts of Indiana where harvest was late and crops began to lodge, Fisher notes. The secret to controlling it as a weed is to get it early, he insists. Otherwise, it can cause considerable yield loss competing with soybeans.