Recent high rainfall in some valleys has seen an increase in regrowth for many cotton fields due to delayed defoliations and picking. Cotton regrowth before harvest can delay picking, reduce picking efficiency, and increase moisture in modules that may negatively affect fibre quality. Regrowth is often a result of warm and wet conditions that allow for cotton to start growing again, as there is no load on the plant from the bolls, as they are now mature.   Nutrients left in the soil also help support new growth.  Effective management involves avoiding regrowth by promoting senescence, timing defoliation, picking optimally, and selecting appropriate harvest aids.

What Causes Regrowth?

• Excess nitrogen: Promotes vegetative growth over senescence.
• Late-season rainfall or irrigation: Triggers hormonal imbalance and fresh vegetative growth.
• Mild weather: Extends the growing season and delays natural crop senescence.
• Delayed picking: Increases the window for regrowth to establish post-defoliation.

Management Strategies

1. Promote Senescence

• Aim for a high boll load to deplete energy stores and reduce regrowth potential.
• Avoid excess nitrogen, especially late-season. Cut off N by mid-flowering.
• Manage irrigation to reach refill point by defoliation. Avoid watering after cutout.

2. Timely Defoliation & Picking

• Use NACB (Nodes Above Cracked Boll) or % open boll to guide defoliation timing.
• Pick as soon as possible after leaf drop to minimise regrowth and fibre exposure.

3. Use the Right Harvest Aids

• Thidiazuron + Ethephon combination: Effective against regrowth and promotes boll opening.
• Ensure adequate spray coverage—harvest aids are non-systemic.
• Desiccants (e.g., diquat, sodium chlorate) can be used post-defoliation if harvesting is delayed, but they:
  • Do not prevent new regrowth.
  • Can increase trash content by leaving dead leaves attached.

Watch the Weather

• Cold nights (<15°C) significantly reduce defoliant performance.
• Warm, sunny days help drive the hormonal response for clean leaf drop.
• Rain soon after defoliation promotes regrowth—adjust timing accordingly.

Consequences of Poor Regrowth Management

• Moist modules: More plant moisture means higher module moisture, risking microbial degradation, staining, and classing penalties.
• Increased leaf trash: Regrowth and poorly senesced crops retain leaves longer.
• Fibre quality loss: Delayed picking can expose lint to weathering, reducing colour grade.
• Operational inefficiencies: Dense regrowth slows pickers and increases contamination (which may affect gin turnout).

Any further questions? Contact your local CSD Extension and Development Agronomist.