Defoliation/desiccation is the final phase in preparing the cotton (Gossypium hirsutum) plant for harvest. Harvest aid chemicals are used in this phase to promote rapid boll opening and to prepare the crop for early harvest. These chemicals are generally classified as herbicidal (injure or stress the leaf stimulating ethylene synthesis. e.g. DEF/Folex) or hormonal (direct effect on the Auxin, IAA e.g. Dropp).