Grass Control Question in Peanuts

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Question: 

Here’s the question- can we tank mix both Intensity and Dual to kill grass in peanuts in order to save a spraying?

Answer (after a phone discussion): 

Dual Magnum and generic Duals as well as Outlook can be applied with clethodim or sethoxydim (various formulations, these are the selective grass herbicides that have been around for a long time, often referred to by their original trade names – Select and Poast.) We have not seen increased peanut injury or decreased grass control when these residual herbicides (Dual Magnum or Outlook, they have no foliar activity) are mixed together. Warrant is also a chloroacetamide herbicide that can be applied with postemergence herbicides. We have not looked at Warrant plus clethodim or sethoxydim. I suspect the active ingredient in Warrant will have no impact but it is applied at 3 pints per acre (like Lasso and Intro used to be applied) and that has a lot of inert material in the formulation going into the tank at that rate. We have not looked at this combination but might do so later this year. But based on our work we have seen no major issue relative to grass control or peanut injury with the mixtures of the selective graminicides we use in peanut with Dual or Outlook.

Also in the conversation I found out that Storm had been applied a few days ago. The Blazer part of Storm will always burn foliage enough so that you need to let the grass recover from the burn before applying the sethoxydim or clethodim. To kill grasses the graminicide has to be absorbed and translocated to meristematic tissue. Also, the Basagran in Storm can affect absorption when applied a few days prior. All this to say try to ask as many questions as you can about the status of the weeds and crop when making a recommendation. Had I not known about the Storm being applied I might have said go ahead and spray, say sethoxydim plus Dual ASAP, with the result being less control than desired. The reduction in control would have resulted from the injury of the grass from the Blazer (in the Storm applied earlier this week) and not from the Dual. But I am sure the Dual would have been blamed for the problem. The clethodim plus Dual mixture needs to go out early this coming week in this case. Also, crop oil needs to be applied with graminicides regardless of what is mixed with them.

Intensity One is a generic clethodim.

One can apply the graminicide just a few days before a contact herbicide (Storm, for example) and have no negative impact on grass control (the active ingredient in the grass herbicide gets absorbed and translocated before the foliage is burned by the contact herbicide.) Also, the grass herbicide rate can be increased by 25-50% and overcome the antagonism. But this is label specific.

Article first appeared as North Carolina Peanut Note (PNNC-2014-068)