Defoliation is the application of chemicals to encourage or force cotton leaves to drop from the plant in order to harvest the crop in a timely manner. Defoliation is a balancing act between killing the leaves and not affecting the leaf. For successful defoliation, the leaf must stay alive long enough to begin the formation of an abscission zone that results in leaf drop. If the leaf is killed too rapidly, the chemical signals are not sent from the leaf to the abscission zone. The result is a leaf that is desiccated and often frozen or “stuck” to the plant, creating unnecessary trash. Cotton defoliation is the goal of harvest preparation for spindle harvested cotton. Desiccation and defoliation may be desired in cotton to be harvested with cotton strippers.

Every season is different and growers must always consider the crop conditions as well as the environmental conditions before deciding on chemicals to use. The chemicals used in a specific defoliation mixture should vary based on conditions and whether boll opening or regrowth inhibition is justified or desired.

Cotton defoliation has at times been described as more art than science. There is some truth to that, but some basic principles do apply to any successful defoliation program. The following interactive learning lesson will highlight some of the science behind the art of cotton defoliation.

Cotton Defoliation Learning Lesson