Flumioxazin Injury on Peanut Peanut Notes No. 45 2018
This time of year you will most likely begin seeing some injury from flumioxazin. The most popular formulation of this active ingredient is Valor SX but there are also several other formulations available. In my experience the injury is transient and in some cases you can see severe injury and come back the following week and the peanuts look fine. Valor SX is a PPO-inhibiting herbicide with residual activity, so what you see looks somewhat like Cobra or Ultra Blazer (the chlorosis and necrosis) but there are other symptoms that are more unique for this type of herbicide applied to soil as it impacts emerging seedlings. We have had a considerable amount of rain over the past week and injury has occurred as peanuts began to emerge. We generally see the greatest injury potential when it does not rain until about the time peanuts begin to emerge. The harder the rainfall and the more rain we receive the greater the injury potential. You can also see a plant with little injury right beside a plant with a significant amount of injury. This often reflects the time of emergence relative to application and rainfall. Sometimes it can take an entire month for all of the peanuts in a field to emerge.