3 MIN READ
Replanting Cotton Following Application of Acetochlor and Fomesafen
February 16, 2021
Growers should be aware of the potential of previously applied herbicides to injure replanted cotton.
Cotton can be replanted in fields previously treated with acetochlor and/or fomesafen herbicides, but crop injury could occur.
The value of weed control provided by these products is generally greater than any losses resulting from cotton injury that may occur.
Controlling weeds after replanting should be a priority.
Replant Concerns
Unfavorable weather conditions can damage or kill cotton seedlings, and replanting may be necessary. Herbicide applications made prior to replant should be considered along with plans to maintain weed control after replanting.
Warrant® Herbicide
Warrant® Herbicide is a microencapsulated formulation of acetochlor and can be applied preplant, at-planting, preemergence, and postemergence in cotton. The recommended rate is 1.5 quarts per acre and two applications can be made per season in cotton. The label for Warrant Herbicide states that cotton can be replanted immediately if the crop treated with this product is lost, but crop injury could occur. Conditions that do not favor adequate crop growth or cause stress (cold, wet soils), or under waterlogged conditions from excessive irrigation or rainfall, are usually the cause of crop injury with preplant or preemergence use of this product. However, good crop safety is generally observed with the use of Warrant Herbicide in cotton. Contact your local Technical Agronomist or Extension Agent for local recommendations.
Warrant® Ultra Herbicide
Warrant® Ultra Herbicide is a capsule suspension formulation of microencapsulated acetochlor with fomesafen. The product can be applied preplant, at-planting, preemergence, or post-directed in cotton, but only once in a growing season. Warrant Ultra Herbicide may only be applied at-planting or preemergence to cotton grown in coarse textured soils (sandy loam, loamy sand, sandy clay loam). In heavier or medium to fine textured soils, the product may be applied preplant up to 21 days prior to planting cotton. A minimum of 0.5 inch of rainfall or overhead irrigation is required after application and before planting. Cotton plants are tolerant of preplant or preemergence applications of Warrant Ultra Herbicide when the product is applied at labeled rates and according to application use directions. Cotton can be replanted in fields previously treated with Warrant Ultra Herbicide immediately in fields with coarse textured soils or after a month in fields with medium or fine textured soils.
Fomesafen, a diphenylether herbicide, can cause stunting, foliar necrosis, and possibly some stand loss in cotton.1 The amount of rainfall or irrigation that occurs from planting through emergence can be related to the level of injury that may occur. Although some crinkling or spotting of cotton foliage or stunting may occur, cotton plants usually outgrow these effects and develop normally. Generally, the value of using fomesafen for effective weed control is greater than losses resulting from any crop injury that may occur. Contact your local Technical Agronomist or Extension Agent for local recommendations.
Controlling Weeds after Replanting
Controlling weeds after replanting should be a priority. Within a few weeks after application, Warrant Herbicide and Warrant Ultra Herbicide will begin to lose their effectiveness for preemergence weed control. If Warrant Herbicide was previously applied, Warrant Herbicide or Warrant Ultra Herbicide could be applied preemergence after replanting for residual weed control. If Warrant Ultra Herbicide was previously applied, only one additional application of Warrant Herbicide can be applied after replanting, and no additional applications of Warrant Ultra Herbicide may be applied. Overlapping residual herbicides with different sites of action throughout the season should be used to maintain weed control and for purposes of resistance management.
Source:
1 Main, C.L., Faircloth, J.C., Steckel, L.E., Culpepper, A.S., and York, A.C. 2012. Cotton tolerance to fomesafen applied preemergence. The Journal of Cotton Science 16:80-87.
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