The 2020 growing season was a challenge for many Iowa growers due to the drought conditions during most of the season and the Derecho storm that occurred on August 10, 2020 (Figure 1). The Derecho flattened millions of acres of corn in addition to having a huge impact on grain storage and building infrastructure. Many fields were able to be harvested; however, it was slow going and some fields had to be destroyed because they were not mechanically harvestable. With the fall activities done, now the question becomes what should I do for the 2021 crop in Derecho damaged fields?
The best option would be to plant soybean if your operation and rotation allows. Planting soybean provides the best advantage to controlling the volunteer corn from the Derecho and can help lower corn rootworm pressure in fields that have been corn on corn. There are more herbicide options for controlling grasses in a soybean crop, especially the use of the ACCase inhibitors (Group 1) herbicides. These herbicides are the most effective when volunteer corn is 12 inches or less in height, (consult the specific herbicide’s label for exact measurements). In addition to the herbicide options for controlling volunteer corn, an additional advantage is lowering the corn rootworm population in these fields. Rotation to a non-host crop can help disrupt the corn rootworm’s life cycle and reduce the number of corn rootworms in that field in 2022, but only if the volunteer corn is controlled.
If you are unable to plant soybean, there are still some options for corn on corn fields. It is important to know the herbicide trait package of the corn planted in 2020 compared to the 2021 crop. For example, if the 2020 corn had glyphosate herbicide tolerance, then consider planting a glufosinate tolerant corn product in 2021 so a glufosinate herbicide application can control the glyphosate resistant volunteer corn. It is VERY important to know the trait package of the 2020 corn crop and the 2021 corn crop, PRIOR to any POST herbicide application for in-season control of volunteer corn. If the herbicide tolerant trait package is the same in both the 2020 and 2021 corn crop, then there are still a few options. Hopefully some fall tillage was able to be accomplished. By tilling in the fall, the volunteer corn kernels were buried so they could either 1) have germinated in the fall and were killed by the frost/freeze of winter, or 2) can germinate early this spring and can be killed with a PRE-emergence herbicide application. If fall tillage was not able to be accomplished, studies have shown that some of the kernels on the ground’s surface should be lost to predation over the winter. Early spring tillage (as early as possible) should be considered to bury the corn kernels so they germinate and can be controlled with a PRE-emergence herbicide application prior to planting the 2021 crop. The use of a non-selective herbicide or Group 1 herbicide should be used in this pre-emergence application; however, it is important to check the plant back time frame for each herbicide used and that the herbicide can control volunteer corn. The last option, if spring tillage and pre-emergence herbicide is not possible, is to plant the 2021 crop as early as possible so it can establish quickly and shade out the volunteer corn.
Michel, J. and Licht, M. 2020. Fall management options for corn fields that are unharvestable. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/.
Jha, P., Hartzler, B., and Anderson, M. 2020. Management of volunteer corn in fields affected from Derecho. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/.
Hodgson, E. 2016. Approaches for managing corn rootworm in Iowa. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/.