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New Mexico State University

Weed Management in Cotton Under the BXN® System

Guide A-234

Richard D. Lee, Extension Weed Scientist
Shane T. Ball, Extension Agronomy Specialist

College of Agriculture and Home Economics New Mexico State University

This publication is scheduled to be updated and reissued 6/04.

Weed management in cotton has taken a new twist with the introduction of transgenic cotton. Some cotton plants have been genetically altered to make them tolerant to a particular herbicide.

One cotton-herbicide system is built around Buctril®  4EC (bromoxynil)-the BXN® System. Research has demonstrated that this system is an effective tool for the management of many broadleaf weeds, including annual morningglory species (Ipomoea spp.), buffalobur (Solanum rostratum), cocklebur (Xanthium strumarium), jimsonweed (Datura stramonium), and spurred anoda (Anoda cristata)-weeds common to many New Mexico cotton fields. In addition, BXN may provide some control of kochia (Kochia sco-paria) and pigweed species (Amaranthus spp.), though the size of the weed is critical in achieving good results.

The marketer of BXN® cotton varieties are Stoneville Texas and Pedigreed Seed. BXN® cotton contains a gene that produces nitrilase, an enzyme that gives cotton the ability to metabolize the bromoxynil herbicide when applied over-the-top to the emerged crop.

Application Information

  • Timing: Broadcast or banded
  • Spray volume: 15 gallons or more
  • Spray pressure: 40 psi or more
  • Spray tips: Flat fan using a 50 mesh screen
  • Use rate: 0.75 to 1.0 pint (16 fl oz) Buctril® 4EC/acre/application
No more than three (3) applications per growing season:
  • First application should be applied early when weeds and cotton are small.
  • Second application should be applied 10 to 14 days following the first.
  • Third application should be made during the bloom stage, but not later than 75 days before harvest.

No more than three (3) pints Buctril®4EC per growing season.

Guidelines, Precautions, and General Comments

  • Use Buctril® 4EC only on cotton that has been genetically modified for this use.
  • The use of a preplant incorporated (PPI) or pre-emergence (PRE) herbicide is recommended to enhance the level of weed management. Buctril® 4EC will not control grass or nutsedge.
  • Do not exceed two (2) applications before the cotton is 12" tall.
  • Make applications to actively growing weeds in the correct stage of growth. Weeds under stress will not respond well.
  • Cultivation should be delayed 5-7 days following application.
  • Tank mixes:

- The addition of MSMA when the cotton is 3" tall will enhance the activity on pigweed.

- Do not tank mix Buctril® 4EC with post emergence grass herbicides (Fusilade DX®, Poast®, Poast Plus®,  and Assure II®). Applications need to be made sequentially. If Buctril® 4EC is applied first, wait at least 7 days before making the grass herbicide application. If the grass herbicide is applied first, then wait  3 days before making the Buctril® 4EC application.

- Do not graze any portion of the crop.

- Do not cut crop for seed or fodder.

Rotation Restrictions

  • Following the 1.0 pint/acre Buctril® 4EC application, wait a minimum of 30 days from the date of application before planting rotational crops.
  • Following the application of more than 1.0 pint/acre Buctril® 4EC, only BXN cotton can be planted in the field the following year. As research is completed, this portion of the crop rotation information may be modified.

New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.

Printed July 1999
Electronic Distribution July 1999