Cotton Injury From Early Season Herbicide Applications

Several calls have come in regarding early season herbicide injury in cotton to both myself and Jason Bond.  It is not uncommon to see cotton injury from applications of Sequence or metolachlor products mixed with glyphosate and/or Liberty.  Undoubtedly, the cool, wet weather we have had so far this year has exacerbated injury from herbicide applications in some situations.

Nearly everyone who has grown Phytogen or Stoneville cotton varieties has observed the difference in tolerance to POST applications of Liberty with or without metolachlor or acetochlor products and/or insecticides for thrips.  The unknown in 2015 was tolerance of Bollgard II XtendFlex varieties to POST applications of Liberty with or without metolachlor or acetochlor products and/or insecticides.  Based on preliminary field observations as well as conversations with other Extension Specialists and researchers in the Mid-South, Bollgard II XtendFlex varieties do not appear to be as tolerant to POST applications of Liberty with metolachlor or acetochlor products compared to Stoneville cotton.  However, Bollgard II XtendFlex varieties do appear to be more tolerant to the same herbicide combination compared to Phytogen varieties.  The picture below illustrates damage observed from Liberty + Dual on Bollgard II XtendFlex cotton applied last week in the Mississippi Delta.  The damage is likely due to the addition of metolachlor and the cotton will grow out of this damage.  While it may be unsightly initially, keep in mind cotton is very resilient and can tolerate early season damage with little to no impact on yield.

Many folks are in a difficult position with respect to product selection for weed control.  Most PRE’s that were applied are beginning to dissipate and pigweeds are beginning to emerge in many fields.  This can be seen in the image below which was provided by Tucker Miller.  Cotton that is stressed due to water logged soils is more susceptible to injury from herbicide applications.  To that end, folks are trying to determine the safest option for weed control with respect to cotton tolerance that will provide maximum efficacy.  If you have concerns about crop safety, choose a herbicide program that will provide the least potential injury and control the most weeds.  If that does not include a residual in the current application, make every effort to get a residual herbicide applied as soon as possible.  The question that you must ask yourself is this:  Do I value pigweed control over crop injury or do I value crop safety over pigweed control?  The answer to that question will guide you on your herbicide program.  You may consider leaving metolachlor or acetochlor products out of the tank if you are applying Liberty to cotton that has been struggling due to weather conditions.  However, if you know that you have heavy pigweed pressure coming, the level of crop injury experienced will likely be offset by gains in residual control of pigweeds.