Insect, Pest and Disease Control - Cotton
Defoliation is an often-overlooked process that, if done properly, can pay large dividends. Defoliation is relatively easy in some situations and extremely difficult in others. Defoliation is the application of chemicals to encourage or force cotton leaves to drop from the plant, allowing harvest of the crop in a timely manner. Proper defoliation requires a balancing act between killing the leaves too quickly or not affecting the leaf at all. Successful defoliation requires that the leaf must stay alive long enough to begin the formation of an abscission zone, resulting in leaf drop. Killing the leaf too rapidly results in a leaf that is frozen or “stuck” to the plant, creating unnecessary trash.
"W075-Cotton Defoliation Timing," The University of Tennessee Agricultural Extension Service, , http://trace.tennessee.edu/utk_agexcrop/88