Sorting Out PPO Herbicides

PPO-herbicides (Group 14) used in this area include Sharpen, Valor, Authority, Reflex, Blazer, Cobra, Aim, and Cadet. In addition to the single active ingredients, there are a number of premixes containing these PPO herbicides. This group is quite varied so making generalizations about these herbicides is difficult. PPOs have gained popularity in the past few years to help combat herbicide-resistant weeds.
Here are a few points to know about these herbicides:

• Some provide good residual control (Authority and Valor) others have no residual activity (Aim or Cadet)
• Soil treated with Valor should not be disturbed after application (disrupting the herbicide layer reduces effectiveness), while Authority can be applied to the soil surface or incorporated lightly
• Some are labeled for application prior to planting (Valor or Authority), some only for postemergence (Aim or Cadet), and some can be used either postemergence or preemergence (Reflex)
• While none of the PPOs are considered grass herbicides, Reflex, Valor, Authority, and Blazer control a number of broadleaf species; Sharpen has a fairly narrow range of control (at rates used in soybeans); and Aim and Cadet only provide consistent control of a few weeds (notably velvetleaf)
• PPO-resistant weeds are not very common, but PPO-resistant common ragweed was identified in a few fields in southern Delaware about 8 years ago
• PPOs have a better fit with soybeans than corn (in my opinion), and we should limit their use to soybean production to reduce selection pressure. And with so many PPO herbicides labeled for soybeans, we need to be cautious to not overuse them
  • With ALS and glyphosate-resistant Palmer amaranth, PPO herbicides are one of our better treatments available to control them
    >Do not use more than one PPO herbicide before or at planting
    >If Palmer amaranth is present, Reflex is often needed for postemergence control. Do not use a product containing fomesafen preplant or preemergence if you intend to use Reflex or Flexstar postemergence
• Some of the herbicides have restrictions on use in the region:
  • Reflex, or products containing Reflex, can only be used once every two years
  • Sharpen, or products containing Kixor, have the following restrictions for use in soybeans, with the following days between application and planting:

When considering the use of a PPO herbicide be sure to read the label and follow label instructions. Some of these labels have change a lot in the past year or two and so only refer to the most recent labels. Do not make generalizations for PPO herbicides.