Federally Listed Aquatic Noxious Weeds (Selected)
| Species | Common Name | Year Listed (Aquatic) | Native Range |
|---|---|---|---|
| Hydrilla verticillata | Hydrilla | 1976 | Asia |
| Eichhornia azurea | Anchored water hyacinth | Listed | South America |
| Salvinia molesta | Giant salvinia | Listed | Brazil |
| Salvinia auriculata, S. biloba, S. herzogii | African / South American salvinias | Listed | South America / Africa |
| Hygrophila polysperma | Indian swampweed | Listed | South & SE Asia |
| Limnophila sessiliflora | Asian marshweed | Listed | Asia |
| Caulerpa taxifolia (Mediterranean strain) | Killer algae | Listed | Aquarium origin |
List is illustrative; for the current authoritative list, see USDA APHIS.
Top Invasive Aquatic Plants in the U.S.
| Species | Growth Form | States Affected | Primary Impact |
|---|---|---|---|
| Hydrilla | Submerged | 30+ | Displaces natives; blocks navigation; alters fish habitat |
| Water hyacinth | Floating | 20+ (mainly Southern U.S.) | Surface coverage; oxygen depletion; flow blockage |
| Eurasian watermilfoil | Submerged | 45+ | Dense canopies; recreation interference; native decline |
| Giant salvinia | Floating fern | Gulf states + spreading | Surface mats up to 3 ft thick; rapid clonal growth |
| Curly-leaf pondweed | Submerged | 45+ | Early-season surge; mid-summer die-off triggers algae blooms |
| Alligator weed | Emergent/floating | 15+ (mainly Southern U.S.) | Shoreline encroachment; mat formation in slow waters |
| Common reed (Phragmites) | Emergent | 48+ | Wetland conversion; biodiversity loss |
Regulatory Framework — Quick Reference
Key Quotable Facts
- Hydrilla was the first aquatic plant federally listed as a noxious weed in the United States (1976).
- The aquarium and water-garden trade is the single largest documented pathway for aquatic plant introduction in the U.S.
- Boat trailers, live wells, and bait buckets are the leading secondary spread pathways between waterbodies.
- Once established, eradication of submerged invasive plants is rare; most state programs aim for long-term suppression below ecological-injury thresholds.
- Federal and state noxious-weed listings do not overlap completely — a species may be regulated at the state level but not federally, and vice versa.
Related Resources on AquaticWeed.org
Ten-Year Lake Management Plan: Lake Wingra, WI
Lake Wingra, a 342-acre urban lake in Madison, WI, developed a comprehensive 10-year management plan coordinating the City of Madison, University of Wisconsin, and adjacent neighborhood associations. The plan addressed Eurasian watermilfoil, curly-leaf pondweed, and purple loosestrife through an integrated approach including targeted herbicide treatment, mechanical harvesting, native plant restoration, and public education.
Key outcome: The structured multi-agency planning process secured consistent funding across multiple budget cycles, a key advantage over ad hoc management. Native plant restoration efforts showed measurable progress in designated restoration zones within three years of initiation.
- U.S. Geological Survey — Nonindigenous Aquatic Species Database https://nas.er.usgs.gov/
- U.S. Army Corps of Engineers — Aquatic Plant Information System (APIS) https://apis.erdc.dren.mil/
- USDA APHIS — Federal Noxious Weed List https://www.aphis.usda.gov/plant-pests-diseases/weeds/noxious
- U.S. EPA — Aquatic Pesticide Use & NPDES Permits https://www.epa.gov/npdes/pesticide-permitting
- Pimentel et al. (2005) — Update on environmental and economic costs of invasive species in the U.S., Ecological Economics 52(3): 273–288. https://www.sciencedirect.com/science/article/abs/pii/S0921800904003027
- Rockwell, H.W. (2003) — Summary of a Survey of the Literature on the Economic Impact of Aquatic Weeds, Aquatic Ecosystem Restoration Foundation. https://www.aquatics.org/publications.html
The ecological impact section helped our team explain to county commissioners why early intervention matters. The oxygen depletion data alone secured funding for our early-detection monitoring program.
Donna Whitfield State Wildlife Biologist, GA · Okefenokee regionWe used the integrated management framework from this site to structure our Eurasian watermilfoil control program. After three seasons we've reduced lake-wide coverage by 78% on our 340-acre water body.
Susan Thibodeau Lake District Manager, MN · Crow Wing County