Cover Crops, Winter Annual Weeds and Spring Vegetables

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Using cover crops prior to early-spring vegetables like peas and sweet corn is becoming more common. One issue for growers who want to no-till into that killed cover is managing winter annual weeds, like henbit and chickweed. In this situation, glyphosate is usually used to kill the cover crops (such as barley, wheat, rye). But glyphosate often will not provide the necessary control of henbit or chickweed because the weeds have not started actively growing that time of year. One way around this is using a herbicide in the fall to “clean up the cover crop”. Using a broadleaf herbicide such as Harmony Extra or 2,4-D in the fall will control many of the broadleaf weeds and not limit crop rotation in the spring (replant intervals are 1.5 to 3 months). Then, when burning down the cover crop in the spring, the concern is killing the cover crop, and not worrying about the winter annual broadleaves that can be tough to control that time of year.

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