It is time to start thinking about spring burndown/termination of winter cover crops, especially tillage radish. The past winter was relatively mild compared to normal and the recent warm weather has initiated spring greenup of many winter cover crops, including tillage radish. Typically, early planted tillage radish (planting prior to Oct. 15th) will get large enough prior to the cold winter temperatures of December and January to provide adequate control due to winterkill. However, the mild temperatures this winter resulted in very little winter kill, even to larger radishes that would die with normal winter temperatures, even in southern Arkansas (Picture 1). Herbicides should be applied to tillage radish prior to flowering to prevent seed dispersal and the potential for volunteer radishes in successive crops. Now is the time to start planning your burndown options for tillage radish as they will soon start to bolt or flower, which often times makes them much harder to kill. Picture 2 shows the flowering structure on tillage radish immediately prior to bolting or when the flowering structure starts to extend out of the rosette and grow upwards from the base of the plant. In our experience, it is best to apply your herbicide prior to this flowering structure reaching more than 4-5 inches in height.
Current recommendations are to apply 1 qt/A glyphosate with 1 qt/A 2,4-D and apply before flowering for adequate burndown.
Due to the lack of winter kill in most fields it is imperative that you start planning these burndown applications to tillage radish now before they start to flower. After flowering, tillage radish become much harder to control with herbicides and producers are often left with mechanical control as their only option.
Picture 2. Flowering structure in the center of a tillage radish rosette. These flowers will start to form immediately prior to bolting. Once tillage radish begin to bolt- or this flowering structure extends upward from the center of the rosette, tillage radish become extremely hard to control with herbicides.
We are continuing to work with these and other cover crops to improve row-crop performance in Arkansas. This research was supported by the Arkansas Soybean Promotion Board and special thanks to Dr. Jason Norsworthy for contributions to this article.