Texas Invasives

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Federal Noxious Weed

TDA Noxious Weed

TPWD Prohibited Exotic Species

Invasive Plant Atlas of the US

NOTE:

means species is on that list.

Pistia stratiotes

Water lettuce

Synonym(s):
Family: Araceae (Arum Family)
Duration and Habit: Perennial Herb

Photographer: USDA APHIS Archives, Bugwood.org
Source: USDA APHIS

Description

Water lettuce is very easy to identify as it resembles a floating open head of lettuce. It may be found singly or in abundance. The leaves are light green, thick, hairy and ridged. Flowers are inconspicuous and are only seen upon close examination.

Native Lookalikes: Currently no information available here yet, or there are no native Texas species that could be confused with Water lettuce.

Ecological Threat: Severe infestations block light to the water ecosystem, reduce oxygen levels, increase siltation, reduce suitable fish spawning habitat and restrict water flow and boating traffic. Its infestations can create habitats favorable for the spread of water-borne diseases. It can also influence the size structure of planktonic communities, causing a shrinkage of plankton volume.

Biology & Spread: Reproduces by vegetative offshoots that are connected to the mother plant by stolons, which may be 60 cm in length, as well as by the production of seeds. Seeds germinate on the surface of bottom mud and float to the surface within 5 days. As a tropical plant Pistia does not survive freezing conditions. Though the seeds are able to survive in ice at -5oC for a few weeks, germination does not occur below 20oC.

History: In South and Central America, Africa and South-East Asia it is considered an endogenous species. A record in the Northern Territory of Australia from 1887, where a complement of organisms naturally regulates its population. Since P. stratiotes has not been recorded at nuisance levels in this area, it is highly possible that northern Australia is part of the plant's native range. Hwowever, there is strong evidence linking water lettuce to South America since regionally native insects have strong host associations with water lettuce.

U.S. Habitat: Water lettuce invades lakes, ponds and slow moving streams in tropical, subtropical and warmer temperate regions.

Distribution

U.S. Nativity: Introduced

Native Origin: South America to Africa

U.S. Present: AZ, CA, DE, FL, GA, HI, LA, MD, MS, NC, NJ, NY, PR, SC, TX, VI

Distribution in Texas: Reported from central, east, north and south Texas.

Mapping

Invaders of Texas Map: Pistia stratiotes
EDDMapS: Pistia stratiotes
USDA Plants Texas County Map: Pistia stratiotes

Invaders of Texas Observations

List All Observations of Pistia stratiotes reported by Citizen Scientists

OBS# 17966

OBS# 17846

OBS# 2763

Native Alternatives

Management

Preventive: Do not sell, propagate, or move plants. Thoroughly clean boats and equipment before leaving infested waterways.

Physical/Mechanical: Small infestations can be hand pulled. Water drawdowns can be used to desiccate exposed water lettuce on dry shorelines, but the time needed to effectively dry large mats of plants can be long. Mechanical harvesting can be done but the process should be designed to prevent the spread of water lettuce plantlets to other parts of the water body.

Chemical:Contact herbicides such as Endothall and Diquat will act quickly, while systemic herbicides such as Rodeo act slowly. Take care to minimize impacts of herbicide application on native species. Decaying plant material may cause dissolved oxygen depletion.

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Text References

Cai L, 2006. Impact of floating vegetation in Shuikou impoundment, Minjiang River, Fujian Province. Hupo-Kexue, 18((3)):250-254.

Holm LG, Plucknett DL, Pancho JV, Herberger JP, 1977. The World's Worst Weeds. Distribution and Biology. Honolulu, Hawaii, USA: University Press of Hawaii.

Mbati G, Neuenschwander P, 2005. Biological control of three floating water weeds, Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta in the Republic of Congo. BioControl, 50(4):635-345. http://www.springerlink.com/link.asp?id=102853

Parsons WT, Cuthbertson EG, 2001. Noxious Weeds of Australia. Collingwood, Australia: CSIRO Publishing, 698 pp.

Online Resources

Bugwood Network. 2010. Pistia stratiotes. (http://www.invasive.org/browse/subthumb.cfm?sub=3064).

Germplasm Resources Information Network

https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.41496

https://www.invasiveplantatlas.org/subject.html?sub=3064