Simultaneous Cotton and Pigweed Emergence Issues

Darrin Dodds, Extension Cotton Specialist
By Darrin Dodds, Extension Cotton Specialist and Jason Bond, Research/Extension Weed Scientist May 23, 2014 10:18

Planting progress on the 2014 cotton crop has certainly been more timely than in 2013; however, we still lag somewhat being a “normal” planting window.  An issue that seems to be occurring on numerous farms this year is simultaneous cotton and pigweed emergence.  This is happening for a couple of reasons.  Over the last three weeks we have essentially planted in shifts.  We had a few good days to plant which was followed by rainfall which limited field activity.  In addition, the wind has not laid in the Delta for what seems like a month.  These factors combined have resulted in cotton being planted and in some cases no preemergence herbicide being applied behind the planter.  As a result, we are seeing simultaneous cotton and pigweed emergence.  Depending on the technology contained in the seed you are planting, this can create a very difficult situation to manage.

If you are growing a cotton variety containing B2RF technology, your options to manage the situation mentioned above are very limited.  Ina perfect world your over the top options for weed control at this point are glyphosate and Staple.  However, pigweeds in Mississippi are resistant to both of these products.  I would count on no more than 25% pigweed control from Staple.  In some localized areas better pigweed  control has been observed with Staple.  If you have successfully used Staple in the past, it will likely still provide benefit in this situation.  Cultivation is an option for managing these pests in the row middles; however, you will still have issues in the drill.  The only remaining option is that of a hooded sprayer.  On very small cotton your options under a hood are limited as any escapes may injury the cotton crop.

If you are growing cotton containing Widestrike technology, you have the option to apply Liberty over the top to manage these pigweed escapes.  Keep in mind, it is not uncommon to see injury from these applications.  In addition, be cautious when adding other products to Liberty and making applications to Widestrike cotton.  I would not recommend adding a metolachlor (i.e. Dual, Medal, etc.) or acetochlor (i.e. Warrant) product as you will likely see injury from these applications.  I would also not recommend adding AMS to Liberty in these applications as you will likely see injury as well.  Further complicating the situation has been the arrival of thrips in many fields this week.   If you have thrips that need to be treated as well as pigweeds in Widestrike cotton, the following insecticides can be added (in order of safety):  acephate/Radiant, Bidrin, then dimethoate.  The same order of safety applied with respect to insecticide applications to B2RF cotton.  Keep in mind that injury may also appear from these applications.

If you are growing GlyTol/Liberty Link cotton, you can certainly apply Liberty as well as metolachlor (Dual, Medal, etc.) as well as acetochlor (Warrant) and/or a product for thrips if need be.  While a three way combination may result in minor injury, GlyTol/Liberty Link cotton is more tolerant of these mixes than Widestrike cotton.

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Darrin Dodds, Extension Cotton Specialist
By Darrin Dodds, Extension Cotton Specialist and Jason Bond, Research/Extension Weed Scientist May 23, 2014 10:18
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