Defoliant
A chemical that causes plants to shed their leaves, used to facilitate harvesting or clear vegetation.
Abscission: The regulated process by which a plant sheds leaves, flowers, fruits, or other parts. Defoliants induce the separation process at the base of leaves.
Cotton production: The cultivation and processing of cotton plants for fiber and related products. Preharvest defoliation clears leaves so cotton can be picked more efficiently.
Contact herbicide: A herbicide that damages plant tissues where it directly contacts them. Contact injury can resemble defoliation but does not necessarily activate leaf-abscission processes.
Herbicide drift: The movement of herbicide away from its intended target during or after application. Drift can expose nearby crops, habitats, and people to defoliant chemicals.
Chemical warfare: The use of toxic chemicals to injure, incapacitate, or kill people or to damage the environment. Military defoliation made vegetation-control chemicals part of chemical-warfare history.
Ethylene: A gaseous plant hormone that regulates ripening, stress responses, and the shedding of plant organs. Ethylene signaling can promote leaf drop after defoliant exposure.
Mechanical harvesting: The use of machines to gather crops from fields. Removing foliage helps harvesters collect crops with less leaf material mixed in.
Systemic herbicide: A herbicide absorbed and transported through a plant to affect tissues beyond the application site. Systemic herbicides can kill whole plants rather than merely remove their leaves.
Ecotoxicology: The study of how chemicals affect organisms, populations, and ecosystems. It evaluates defoliant effects beyond the treated plants.
Operation Ranch Hand: A United States Air Force operation that sprayed herbicides over Vietnam, Laos, and Cambodia during the Vietnam War. It was the major military campaign that applied defoliants across Southeast Asia.