Over the past couple weeks Penn State University researchers have received calls about the concern over volunteer corn in next season’s crops and what are some possible control options to consider. The concerns are coming from growers in areas that were impacted by flooding, have a lot of downed corn, or are still trying to harvest the crop. One of the most important factors to consider is what kind of corn was grown this past season? Was it a conventional hybrid? Did it have a single or multiple genetically-modified (GM) herbicide trait(s)? Also, what crop do you plan to plant this coming spring? In general, if you plan to rotate to a soybean crop [conventional, Roundup Ready (RR or glyphosate-resistant), LibertyLink (LL or glufosinate-resistant), or STS] then the simplest option would be to include a post-grass herbicide (e.g., Select Max, Assure II, Targa) in with the post herbicide program. However, other herbicide options could be used, depending on the type of soybean variety planted.
If you plan to rotate the field back into a corn crop (corn on corn) then the options can get murky. If the volunteer corn has only the glyphosate (RR) trait, then a hybrid that is LL or Clearfield (IMI) resistant will provide the best option for managing volunteer RR-corn. Most likely, the volunteer corn problem will be a stacked RR plus LL hybrid, and in this case, the best bet would be to plant a Clearfield hybrid and spray with Pursuit or Lightning to help control or suppress the volunteer RR/LL-corn. Another possible consideration would be to plant the problem field(s) last and allow the volunteer corn in the fallow field to germinate then spray with Select Max or possibly paraquat (Gramoxone) prior to planting the crop. Keep in mind, Select Max requires a 6-day wait before the corn crop can be planted and paraquat can be inconsistent and requires good spray coverage to be effective. If you can till, then aggressive moldboard tillage can bury the seed or in-crop cultivation can provide some control of the volunteer corn between the rows.
This will only get more complicated once Enlist corn (Dow AgroSciences) and Optimum GAT corn (DuPont/Pioneer) come to the marketplace. These hybrids will likely have resistant trait combinations that could be tricky to manage as well. As you prepare to purchase corn hybrids for next season, remember to keep some of these factors in mind.
Although the above management options are very general and as volunteer GM-corn becomes more of an issue, there will be some creative approaches to this problem.