Approximately 19 years ago, Valor, or flumioxazin, was first registered for use in peanut. Since then, it has become one of the most commonly used peanut herbicides.
According to a recent USDA/NASS survey about pesticide use in peanut, Valor is applied to 74% of the peanut acres in Georgia (65% across the Peanut Belt).
Despite its popularity with growers, there is often some trepidation, and perhaps even occasional heartburn, about the use of Valor in peanuts due to its potential to cause unwanted crop injury. I can vividly remember back in 2001 walking almost every peanut field in Georgia that had succumbed to Valor injury. Unfortunately, that was quite a few acres. Peanut weed scientists across the Belt were scratching their heads because the type of injury that was occurring had not been observed during its discovery and development years. We all dropped the ball on that one!
Since then, a ton of research has shown that seed quality, planting depth, rate, time of application, and rainfall at emergence are the primary factors that influence the degree of Valor injury that can occur. Realistically though, just about every Valor treated peanut field that receives a significant rainfall event at the time of emergence (+ 10-14 days), will be injured to some degree regardless of management.
If you take a quick peek at Figures 1 and 2, you will see the results of one of my 2019 weed-free, Valor/peanut field trials. In this trial, neither 3 oz/A nor 6 oz/A of Valor SX 51WG, despite causing various degrees of injury, had a negative effect on final peanut yield. For the record, 6 oz/A is a 2X labeled rate and should never be consciously applied to any peanut field! Over the past 23 years of conducting research with Valor on peanut, I frankly cannot find any of my own data where the use of the labeled rate of 3 oz/A has resulted in significant yield losses.
Depending upon your location, specific weed control needs, and time of planting, a combination of a residual grass herbicide, such as Prowl (pendimethalin) or Sonalan (ethalfluralin) or Dual Magnum (S-metolachlor) or Warrant (acetochlor), + Valor is a fantastic preemergence weed control program to help get your 2020 peanut crop off to a great start!
Valor has become the most widely used peanut herbicides for good reason (excellent Palmer amaranth and Florida beggarweed control).
I am almost certain that Valor will cause undesirable peanut injury again in 2020 with the right weather conditions. But fortunately, research continues to confirm that injury from the labeled rate should not result in significant peanut yield loss. To minimize Valor injury in peanuts, plant high quality seed at least 1.5 inches deep and apply Valor immediately after planting (but not later than 2 days after planting).
As always, good weed hunting.