When you’re considering the various cotton harvest aids available it’s important to remember the objectives that include defoliation, boll opening, inhibition of regrowth, and weed desiccation. Selecting appropriate cotton harvest aids can be among the toughest, but most important decisions a cotton producer will have to make. There are few products that can accomplish all of the objectives at once. A combination of harvest aids usally are required.
Early defoliation can be critical in maximizing the yield. However, delaying defoliation allows immature bolls to develop, thus increasing the yields. Timing of defoliation impacts characteristics of cotton quality. Defoliating too early or late can negatively impact fiber quality, including micronaire and staple.
Cotton harvest aids usually are either herbicidal or hormonal. Herbicidal compounds like Aim, Def, Folex, Harvade, and ET will injure the plant, reducing auxin levels and stimulating ethylene production. Ethylene will cause the leaf to form an abscission layer and drop from the plant. Examples of hormonal defoliants are Dropp, Freefall, Finish, Cottonquick, and Prep. These promote synthesis of ethylene in the plant.
Boll opening aids such as Ethephon 6, Prep, Super Boll, CottonQuik, and Finish (ethephon) enhance the activity of defoliants and hasten the opening of mature bolls. Thorough coverage is essential as these aids are not systemic. Ideally cotton should be picked 7 to 14 days following application of boll opening aids. Paraquat (Starfire) can enhance defoliation of juvenile growth when applied along with other defoliants but you must pick within 7 days when using paraquat to avoid bark contamination.