A mild winter (again) has given cool season (winter annual) weeds a great opportunity to survive and grow. This is evidenced by the lush growth of chickweed, henbit, mustards (many species), speedwells, prickly lettuce, marestail (officially horseweed), and downy brome. This is also true of winter annual crops or cover crops such as winter wheat, rye, and hairy vetch. Cool season perennials such as Canada thistle, curly dock, and dandelion have weathered the winter quite well. Early summer annuals such as ragweeds (giant and common), smartweeds, and lambsquarters are joining the winter annuals and cool season perennials to provide "ground cover."
Know Your Enemy, Choose Your Weapons
The big no-till question revolves around what "burndown" treatment will control these weeds. 2,4-D is excellent on most mustards, prickly lettuce, and marestail, but chickweed and henbit are not its forte. Dicamba (Banvel or Clarity) and atrazine are better on chickweed and henbit. The forte of glyphosate (Roundup Ultra, Touchdown, Glyfos, Credit, etc.) is grass control, but it can control many broadleaf weeds at higher rates, and the addition of 2,4-D or dicamba may also improve broadleaf control. Gramoxone Extra alone or with atrazine (improves mustard and smartweed control) can also be used. Table 5 is reprinted from the 1999 Illinois Agricultural Pest Management Handbook and provides ratings for various burndown herbicide options on several weed species.
Read the Label for 2,4-D Products
Even though the active ingredient may be the same, not all formulations of 2,4-D have identical uses allowed on their respective labels. Always consult the label of the 2,4-D product you intend to use for allowable uses, rates, and restrictions.--Marshal McGlamery, Aaron Hager