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With the onset of planting season, it is necessary to watch for winter annuals and early emerging summer annuals in corn and soybean fields. Consider applying burndown herbicides to control those weeds when temperatures are above 55 F to improve the effectiveness of herbicide application.

As emphasized during the Crop Advantage Series presentations and other ISU extension meetings across Iowa in January/February, two key herbicides, glyphosate and glufosinate, are in short supply to many of the corn and soybean producers. Therefore, the 2022 growing season is going to be different from any normal year and we need a game plan! Currently, glyphosate and glufosinate are the two most widely used herbicides in corn and soybean.

Most herbicide labels caution against applications made under environmental stress such as prevailing hot and dry conditions in Iowa this year. This is because of increased risk of crop injury and/or decreased weed control. Weeds growing under hot, dry conditions are often difficult to control because of the development of a thicker waxy cuticle, which serves as a barrier for herbicide absorption. Such conditions can also reduce herbicide movement inside the plant due to slowed rates of translocation and metabolism.

The following is a brief summary of new products available for weed control in corn and soybean in 2021. None of these are new sites of action herbicides, but are new premixes or revised formulations of existing active ingredients.