Manage Weeds on Prevent Plant Acres

With about 31 million corn acres yet to plant, it’s likely we’ll see more prevent plant acres than ever before. This record number of prevent plant acres comes with not only financial challenges, but agronomic challenges as well.

Perhaps the most offensive? Weeds. Farmers in areas with a considerable amount of prevent plant are undoubtedly seeing the pests rear their ugly heads across barren fields.

Winter annual weeds are what farmers will see right now, and are likely close to seeding, but summer annuals are beginning to germinate and could soon be problematic. These weed seed banks can survive for years.

“The old weed science adage ‘one year’s seedling equals seven years weeding’ reinforces the need to adequately manage weeds on prevented planting acres,” said Aaron Hager, University of Illinois Extension weed scientist in a recent blog post.

Hager outlines four management techniques to help farmers gain control over problematic weeds. While it can be a financial strain to control weeds on unplanted acres, it’s critical to set fields up for success in years to come.

  1. Tillage: Certain types of tillage can bury and destroy weeds that have already germinated. Hager warns vertical tillage equipment might not get the job done, but tandem disks, field cultivators and other soil-moving tools should. While tillage does a good job of killing emerged weeds, it might also stimulate germination and emergence of other weed seeds, so it might require multiple tillage passes to prevent summer annuals from going to seed.
  2. Mowing: This practice can help suppress weed growth but might not effectively stop seed production of all summer annual weeds. Some weeds will regrow or run tillers below cutting height. If you use this practice, run the mower as low as possible. Hager recommends mowing, followed by tillage.
  3. Herbicides: Watch for herbicide resistance before selecting herbicides. Consider talking to a local agronomist to learn what resistance is in your area. Hager recommends combining glyphosate with 2,4-D or dicamba to provide consistent control of emerged waterhemp, marestail and giant ragweed. Because pigweed species have extended emergence periods it will require two to three herbicide applications before frost.
  4. Cover crops: Species such as rye, wheat, sudangrass or other well-established grass cover crops can limit weed emergence. Control weeds before planting cover crops to give them the best start.