Postemergence Weed Control Peanut Notes No. 83 2020

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As we move into the latter part of June there will be a shift away from paraquat as an option for postemergence weed control in peanuts. Applications need to be made within 28 days after emergence but generally earlier is more effective (weeds are smaller) and risk of peanut injury is less. Storm plus 2,4-DB is a good option but if Palmer amaranth is relatively large you will need to include more Ultra Blazer with Storm. Cobra is a good option in many fields. Cadre continues to provide good control of sicklepod, nutsedge, morningglory and in some fields pigweeds. However, in many fields you need to assume ALS resistance and include Ultra Blazer or Cobra with Cadre. To kill the pigweeds, especially Palmer amaranth, you need to target small weeds.

In many fields, especially after this week’s rains, there will be grass escapes. Clethodim (active ingredient in numerous formulations on the market) is the primary selective grass herbicide. Sethoxydim (Poast and Poast Plus) is labeled but is generally not as broad spectrum as clethodim. Cobra, Ultra Blazer, Storm, and Basagran can reduce control with both of these grass herbicides. Sequential applications with the grass herbicide first and the broadleaf/sedge herbicide 3 days later often provides the best results for grass control (but the broadleaf weeds, especially Palmer amaranth can get very big in just a few days.)  If you apply grass and broadleaf herbicides in a mixture, increase the grass herbicide rate by 50% to compensate for the antagonism. Although some clethodim labels indicate that surfactant rather than crop oil concentration can be used, in my experience the most consistent performance occurs when clethodim is applied with crop oil concentrate, especially when applied in mixture with other herbicides. In some instances greater burn of peanut foliage occurs when Cobra, Storm, and Ultra Blazer are applied with crop oil concentrate, but this is transient and not an issue for peanut growth and development.

If grasses are relatively small and you are applying Cadre, I suggest letting the Cadre provide as much control as possible. In many instances you will not need clethodim. Cadre can reduce control by clethodim but Cadre also provide good control in and of itself.