been reported as noxious weeds, including A. angustifolia, A. caracasana, A. denticulata, A. nana, A. nodiflora, A. paronychioides, A. philoxeroides, A. sessilis, A. tenella, and A. triandra. The most important species is alligator weed (A. philoxeroides), a South American aquatic plant that has spread to other continents. It is a weed of many kinds of agricultural crops, it is an invasive species that degrades native habitat, and its dense mats of vegetation clog waterways, slowing shipping and increasing flooding. Alternanthera plants are known to produce allelopathic compounds that injure other plants, including crops. Biological pest control agents now in use to reduce alligator weed infestations include the alligator weed flea beetle (Agasicles hygrophila), the alligator weed thrips (Amynothrips andersoni), and the alligator weed stem borer (Arcola malloi). Uses A. philoxeroides and A. sessilis are eaten as vegetables in parts of Asia. Some Alternanthera are used as ornamental plants. References Amaranthaceae genera