Alternanthera philoxeroides, commonly known as alligator weed, is an emergent aquatic plant. It originated in South America, but has spread to many parts of the world and is considered an invasive species in Australia, China, New Zealand, Thailand, and the United States.
Alligator weed can grow in a variety of habitats, including dry land, but is usually found in water. It may form large interwoven mats over the water or along shorelines. Alligator weed stems are long, branched, and hollow. Leaves are simple, elliptic, and have smooth margins. Alligator weed flowers during the warm months of the year and has whitish, papery ball-shaped flowers that grow on stalks.
When alligator weed invades waterways, it can reduce water flow and quality by preventing light penetration and oxygenation of the water. It can also reduce water bird and fish activity and cause the death of fish and native plants. Alligator weed mats create a favorable habitat for breeding mosquitoes. Alligator weed is also difficult to control.
Insects have been released for the biological control of alligator weed. The most successful and widely used is Agasicles hygrophila commonly called the alligator weed flea beetle; it has been released for biocontrol in Australia, China, Thailand, New Zealand, and the United States. Amynothrips andersoni, the alligator weed thrips, and Vogtia malloi, the alligator weed stem borer, have also been released in the United States.
- "Alternanthera philoxeroides information from NPGS/GRIN". www.ars-grin.gov. Retrieved 2008-08-09.
- Stewart, C.A.; Chapman, R.B.; Frampton, C.M.A. (2000). "Growth of alligator weed (Alternanthera philoxeroides (Mart.) Griseb. (Amaranthaceae)) and population development of Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae) in northern New Zealand.". Plant Protection Quarterly 15 (3): 95–101. ISSN 0815-2195.
- Everitt, J.H.; Lonard, R.L.; Little, C.R. (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press. ISBN 0-89672-614-2.
- University of Florida, Aquatic Weed Management Guide. Biological Control with Insects
- photograph, description and diagram from HerbiGuide
- Species Profile- Alligatorweed (Alternanthera philoxeroides), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Alligatorweed.
- Alternanthera philoxeroides (Mart.) Griseb. Medicinal Plant Images Database (School of Chinese Medicine, Hong Kong Baptist University) (traditional Chinese) (English)