Clethodim and Enlist® herbicide antagonism on volunteer corn

Graminicides are antagonized when mixed with phenoxies, with the 'fop' based products unable to bring about acceptable levels of control when mixed with Enlist® herbicides.  The 'dim' products (ie. ARROW ALL IN® - clethodim) will also experience a slight reduction in efficacy when mixed with Enlist® herbicides, but based on work out of the US¹ there are strategies to maintain commercially acceptable levels of control:

1. Conditioning the spray water with ammonium sulfate (AMS).  Water quality can impact numerous herbicides, including clethodim.  Certain products are impacted by cations, but with clethodim the concern is actually bicarbonates².  Bicarbonates challenge the uptake of clethodim, but this can be overcome with AMS.  Given so much water is from wells (limestone) many sources tend to have elevated levels of bicarbonate, making conditioning with AMS highly recommended for optimal efficacy.
2. Higher rates of clethodim.  When targeting volunteer corn, without an Enlist® product in the mix, the lower end of the clethodim rate range is generally used.  However, to overcome the phenoxy antagonism, recommendations out of the US are to use a 1.5-2X rate to maintain 80-90%¹ efficacy (rates are still within the labeled range but at the high end).
3. Diligent use of surfactants.  The ‘dim’ graminicides are generally more difficult to get into weeds than the ‘fops’ so the use of surfactants is crucial to ensure uptake.  The US tends to use higher volumes of surfactants, even above what would be provided by any glyphosate in the mix .  This high importance of surfactants with clethodim is a big part of why ADAMA created ARROW ALL IN®, with built-in surfactant to help ensure quick uptake and optimal performance.
4. Size of volunteer corn.  Clethodim is very effective on volunteer corn, but once the corn gets larger (ie. past your knees) the level of control will drop; with or without an Enlist® herbicide tank mix.

Splitting the applications of graminicides and 2,4-D when targeting volunteer corn is another option, but one that may not be viable in terms of time, sprayer capacity, etc.  However, by adapting the practices above good control of volunteer corn can be achieved.

If any questions on this topic, or to learn more about ARROW ALL IN®, please reach out.

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Cited Literature:         ¹2020-NCWSS-Poster-Marcelo-Zimmer.pdf (purdue.edu)

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