Transition to PPO Inhibitors Peanut Notes No. 79 2019

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Transitioning Away from Gramoxone to PPO Inhibitors

We are getting close to the time to move away from Gramoxone to herbicides like Cobra, Ultra Blazer or Storm. This is driven in part by weed size (weeds are growing quickly and weeds need to be small for Gramoxone to be effective) and age of peanuts (apply Gramoxone within 28 days after peanut emerge.)  Annual grasses are often controlled by Gramoxone if they are small. This is not the case for PPO inhibitors, so a grass herbicide (primarily one containing the active ingredient clethodim but also Poast – sethoxydim active ingredient) will likely be needed in some fields (depending on how effective residual herbicides have been in holding back grasses.)  For grass escapes, goosegrass, crabgrass, and Texas panicum are likely the major culprits. With rains over the past weekend in many places clethodim will work well. When applied with PPO inhibitors, increase the clethodim rate to compensate for antagonism. Make sure the correct adjuvant is used with clethodim mixtures. Most products call for crop oil concentrate. Storm, Ultra Blazer, and Cobra can be applied with 80/20 surfactant or crop oil concentrate. Clethodim often performs less effectively when applied with 80/20 nonionic surfactant compared with crop oil concentrate.

Cadre or Impose is applied in many fields. These herbicides (active ingredient is imazapic) do a good job on some of the annual grasses (these herbicides are weaker on goosegrass than the others.)  Before adding clethodim to the mix see what Cadre or Impose will do, keeping in mind that we often need clethodim in many fields later in the season no matter what we do now. Many fields will have ALS-resistant Palmer amaranth, so when Cadre or Impose are applied a PPO inhibitor will be needed. Weeds need to be small for these to work well.