Killing Cover Crops

Mark VanGessel, Extension Weed Specialist;

It is important to be sure cover crops are dead prior to planting. Once the crop has emerged there are fewer options for killing the cover crop. The cool, overcast weather has further complicated terminating cover crops. All herbicides need actively growing plants to be effective, and the recent weather has slowed (or reduced) herbicide activity. Allow 7 to 10 days for glyphosate to achieve maximum effectiveness and scout to be sure burndown programs were successful. Tankmixtures with triazine herbicides or mixtures containing Valor (flumioxazin) can reduce glyphosate effectiveness under poor growing conditions. On the other hand, tankmixing a triazine with paraquat can improve overall effectiveness. When tankmixing, analyze each component herbicide to avoid a reduction in effectiveness. Some growers are planting first and spraying the cover crop after planting. This is a unique situation that requires the proper planter and attachments to manage the residue, and paying close attention to be sure the cover crop does not take up too much moisture before planting. We will be evaluating this concept of “planting green” this spring for both corn and soybeans.