DEFOLIATION TRIAL COMMENTS 

By: Steve M. Brown 

Extension Agronomist-Cotton

The University of Georgia

2003 DEFOLIATION PROJECT SUMMARY

Statistical Summary Page Link

The plots were rated “blind,” meaning without immediate knowledge of specific treatments. 

At some sites, essentially all treatments provided commercially acceptable defoliation and boll opening, confirming the adage, “There is more than one way to skin a cat.”  Moreover, it seems obvious that most entries would perform well – companies have an interest in entering their products at rates and in mixtures expected to perform well.  Gradations of performance are not the purpose of the trials.

It is interesting to note that while many treatments end up the same – leaves off, bolls open – getting there can be quite different.  The visual effects on foliage are very different among the treatments, some being “herbicidal” products that injure the leaf and others being more hormonal in activity, resulting in a change in hormone balance in the leaf/petiole.  In terms of physiological effects on leaves, herbicidal compounds include Aim, DEF/Folex, ET, and Resource; hormonal products include Dropp/Free Fall/Thidiazuron, Harvade, and various ethephon products.

The Bleckley County site was very unusual.  It was defoliated very early in terms of and the site received 4 plus inches of rainfall 4 to 5 days after treatment.  Overall treatment performance was very poor even with some of the “premier” treatments.

Part of the so-called “art” to harvest aid selection is probably related to variation in the field.  Even though these sites were chosen for crop uniformity, as the leaves began to fall and bolls began to open, significant variation became quite obvious, especially in relation to boll opening.  It is interesting to observe variations in plant response (boll opening especially and to a lesser extent defoliation) within the same plot.  Variations may be caused by soil moisture differences, pest management issues, fertility, mechanical injury, etc.  At times, this means observed activity is affected by crop/environment interactions more so than treatment.  Such being true, it is valuable to see defoliation treatments over numerous sites, conditions, and/or replications to form opinions as to what to expect with XYZ treatment.

Within the evaluation period (12 to 13 days maximum), regrowth was inconsequential. 

At 12 to 13 days, the only site almost harvest-ready was the one in Decatur County .

Preconditioning treatments (Folex or Dropp SC + DEF) worked well to remove foliage and expose upper bolls, but within the time of evaluation did not expedite boll opening.  If ever we’ve had a year in which preconditioning was warranted, it has been 2003.