Dr. Bob Scott: I’m Bob Scott with the Cooperative Extension Service, Division of Agriculture. Corn is an excellent rotational crop with soybeans and cotton, especially if you’ve got Palmer pigweed. In corn we can use products such as atrazine, halex GT, which contains several modes of action that aren’t available in cotton and soybeans for the control of pigweed.
It’s important to remember in your rotation crops like corn to watch for late-emerging weeds in the corn canopy. As corn begins to mature in the fall, the canopy opens up, the sun is allowed to hit the ground, and we have a reemergence of many troublesome weeds. Often these include Palmer pigweed, morning glories and grasses.
Often times in the fall it’s very beneficial to follow corn harvest with a herbicide application to prevent these late-germinating weeds from going to seed. There are a limited number of products available, especially considering what you want to do with the field the following year. Paraquat or gramoxone is a commonly used product following corn harvest to eliminate pigweed.
If you’re planning on planting wheat you may want to consider including a residual such as Valor. Valor can be applied 30 days prior to planting wheat. In addition to Valor, Dual is an option if you’re not going to plant wheat. Dual can be used in combination with gramoxone following corn harvest to prevent the germination of pigweed seed until we have a killing frost.
For more information about pigweed control consult the MP44 at www.uaex.edu.