There are many ways to kill cover crops. The secret is knowing what the crop is, what you need to add to the tank and what weather conditions are, notes Larry Huffmeyer, a Syngenta rep and farmer. He lives in Ripley County.

Since April and early May weather was cool, he has been receiving calls from dealers working with customers who didn't get the kill they wanted, especially on annual ryegrass. Glyphosate and other products that work on it don't work as well during cool weather. You can't shave rates and you need to add the recommended adjuvants in the tank for best results.

Sign of control: Note the stem of crimson clover on the left. The inside is white compared to the healthy stem that had not yet been sprayed, the stem on the right.

One of the cover crops that Huffmeyer planted last fall was crimson clover. Allowed to grow in the spring, it produces nitrogen for the next crop. However, the key is when to kill it, he says.

In early May he planted about 20 acres into crimson clover. Then he sprayed a burndown including Touchdown to knock out the clover. Some 10 days later it was apparent that most of the clover was dying, but it wasn't all dead yet.

"Let's check some plants and see if they're dying, even if they're not dried up yet," Huffmeyer notes. He pulled a crimson clover plant from an area that had not been planted or sprayed yet. Then he pulled a plant from the part of the field that had been planted, then sprayed with Touchdown and the proper additives.

"The secret is what we find when we slice the stem open," he says. "If it's still green and healthy, then it is alive and hasn't been damaged or controlled.

"If the stem is whitish to brownish then the herbicide is working and the plant will die. Normally there is also some water or moisture inside the stem on those plants."

Sure enough, when he cut open the stem that had not been treated, slicing horizontally, the cover crop had a green, healthy stem. When he cut open a stem from where herbicide had been applied, the stem was white. There wasn't a lot of moisture, but there was an obvious difference. You can bring down cover crops if you follow directions.

For more, download our free report, Cover Crops: Best Management Practices.