Disodium methylarsonate (DSMA), the disodium salt of methylarsonic acid, is an organoarsenic compound primarily used as a post-emergence herbicide for controlling annual grasses in cotton fields, turf, and non-crop areas. It functions by disrupting amino acid synthesis in target plants, leading to growth inhibition and death. Due to its arsenic content, DSMA is toxic to humans, animals, and the environment, necessitating strict regulatory controls, protective handling, and proper disposal. It also has limited industrial applications as a biocide, in wood treatment formulations, and as an intermediate in the synthesis of other organoarsenic compounds for specialized uses.