Virginia Cotton: Leaf Scorch Mostly Cosmetic

Photo by Kerry Siders, Texas AgriLife Extensions

Leaf scorch is a common observation in young cotton immediately following a spray application.  It is essentially cosmetic even when it is quite noticeable because the next leaves and the root system are completely unaffected.

  • Normal growth and development continues and within a week, the symptoms are covered up by pretty new leaves.
  • The research has consistently shown that cotton can tolerate quite a bit of leaf scorch and yields will not be affected, all the way up to 30% which can look quite severe.
  • The main two components to leaf scorch are the environment, and adding Dual, Warrant, or Outlook to other herbicides.
  • The main reason these 3 herbicides increase scorch is additive. The herbicides we add them to have heavy surfactant loads and when you add these other products together, each one adds a little bit to the puzzle and overall become a more noticeable symptoms when the environment is favorable.
  • The environmental conditions that are most conducive to leaf scorch are also most conducive to good cotton growth which is warm to hot sunny days with good soil moisture and high humidity. This creates fast tender growing leaves that are more sensitive to burn, but are also quick to recover.
  • Dry conditions harden off cotton. Cotton also is harder in the afternoons.
  • Roundup and Liberty have a surfactant load that contributes to scorch of 0 to 5% up to about 10% if the environment is favorable. Adding auxins will likely increase some scorch primarily because you are adding more surfactant.
  • At this point, it looks like Enlist may be the hotter product but is still not as hot as Dual/Warrant/Outlook. We see minor differences in brands and generics that are related to the adjuvant load and not the active ingredients.
  • I saved acephate for last. Even though it gets talked about a lot, acephate does not impact leaf scorch significantly. The research shows Orthene scorch is mostly zero up to 2% with favorable conditions.

In summary

  • We certainly have the environment now for some minor scorching. The basic herbicides we use are safe and Orthene will not change anything.
  • However, when you double up the herbicides, you also double up the surfactant load and more aduvents can be a component. And do not add Dual Warrant or Outlook to these tank mixes until cotton has 2 mature leaves. Even then, you could see 10 to 20% leaf scorch in favorable environments, but this would not impact yield.
  • If you want to stay safe with Dual/Warrant/Outlook, you can spray them by themselves.



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