Skip Navigation
PhytoGen / Cotton Agronomy / Effective timing and efficient defoliation techniques maximize yield and fiber quality

DEFOLIATION IN COTTON: USE A ‘TEAM’ APPROACH FOR OPTIMAL APPLICATIONS

Something went wrong. Please try again later...

PhytoGen explains how the TEAM approach to cotton defoliation — Timing, Environment, Application and Materials — delivers effective, efficient results

Cotton defoliation is as much an art as a science. It involves a visual analysis of the crop and knowledge of the defoliation process, summarized by the acronym TEAM: timing, environment, application and materials. Using judgment based on scouting and experience, growers can apply the best practices for cotton defoliation to maximize yield potential and lint quality.

TIMING

There are several ways to determine the best time to apply defoliants. To check the timing, growers will need to visually inspect cotton plants.

  • Heat units (NAWF 5 + 850 DD60s): Most cotton varieties are ready for defoliation once a plant accumulates 850 to 900 DD60s after cutout, determined by 5 nodes above white flower.
  • Percent open boll: Once 60% of the bolls are open, the plant is considered ready for defoliation application.
  • Nodes above cracked boll (NACB): When looking at a plant, count the nodes from the uppermost cracked boll to the uppermost harvestable boll. If the count is 4 or less NACB, the field is likely ready for defoliation.
  • Sharp-knife technique: Take the highest harvestable boll on the plant and cross-section the boll with a knife or PVC cutting tool. The boll should be difficult to cut, with folded cotyledons, no jelly-like substance, and a visible, darkened seed coat. Watch HERE to see PhytoGen team member Blake McClelland demonstrate the sharp knife test.

Use the above methods together to confirm if a field is ready for defoliation. Remember to check each field, as maturity will fluctuate based on varieties and agronomic conditions.

ENVIRONMENT

Assessing the environment and crop condition is the next step. Weather conditions at the time of defoliation, and three to five days following, have significant impact on cotton response.

  • Crop condition: Plants shouldn’t be under drought stress. If defoliants are applied to drought-stressed crops with tough foliage, results will likely be poor.
  • Weather conditions: Cotton harvest aids are most effective when temperature, sunlight intensity and relative humidity are high. A night temperature warmer than 60 degrees F is especially important. For temperatures warmer than 60 degrees F, the rate of leaf drop roughly doubles for each 10-degree rise in temperature. At least one full day of clear weather following application is necessary to optimize leaf drop.

APPLICATION

The third step in the TEAM approach is selecting the most effective application method for defoliants. In cutout or short-statured cotton, a single application typically should be sufficient to remove leaves and open bolls. Rank cotton may require a two-shot approach: one application to open the canopy, followed by a second application to finish defoliation and open bolls.

With either approach, it’s important to remember that defoliants work on contact, so adequate canopy coverage is essential for performance. Use the following tips to ensure proper coverage:

  • Nozzle selection: Hollow cone or flat-fan nozzles provide superior coverage compared to air-induction nozzles.
  • Water volume: 10 gallons per acre by ground and 5 gallons per acre by air are the recommended minimum water volumes.
  • Defoliant labels: Defoliant labels provide information on spray pressure, ground speed, and necessary environmental conditions. Read and follow labels to ensure adequate coverage and product performance.

MATERIALS

The last step of this process is to pick which harvest aid material would be best for the selected cotton field. Because field conditions are highly variable, work with your local team of PhytoGen field agronomists, consultants, retailers and Extension to determine the right defoliant for your situation.

Types of harvest aids:

  • Hormonal defoliants: These increase ethylene synthesis, resulting in leaf drop, and are less likely to cause “leaf stick.”
  • Herbicidal defoliants: These cause leaf injury, resulting in ethylene synthesis and leaf drop.
  • Desiccants: Typically used in stripper cotton, they’re used to dry down plant tissue for harvest.

Once a harvest aid is selected, good field planning will help you stagger applications for a successful harvest. Use these guidelines to aid in field planning and defoliation timing:

  • Do not defoliate all cotton fields at the same time.
  • Apply defoliants 10 to 14 days prior to the anticipated harvest date for each field.
  • Leaf drop should begin about four days after application and be complete in about 10 days. Check fields after application to determine if a second application may be needed.

CONTACT YOUR LOCAL FIELD AGRONOMIST

As you follow the TEAM approach outlined above, our PhytoGen experts are available to help you make the right decisions to drive cotton harvest success. To connect with your local PhytoGen field team member visit PhytoGen.com/Team.

AGRONOMY

Find information on yield and more in the PhytoGen Cottonseed Agronomy Library. 

EXPLORE LIBRARY    

MORE TIPS TO THRIVE