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Click drainages to open a larger map in a new window.
Map indicates recorded presence in at least one site within the drainage (USGS Hydrologic Unit 8)
but does not necessarily imply occurrence throughout.
Salvinia molesta (giant salvinia) has been recorded, since 1995, from over 90 locations in 41 freshwater drainage basins of Texas, Louisiana, Mississippi, Alabama, South Carolina, North Carolina, Georgia, Florida, Arizona, California, Virginia, and Hawaii.
Time Series Map: Salvinia molesta
Distribution summaries, highlights, and updates follow:
South Carolina
1995
Broad-St. Helena Drainage: Salvinia molesta first recorded outside of cultivation in the United States (Johnson 1995). The 1.5 acre infestation at a private pond was chemically removed within a year, before plants had spread locally. Absent for over five years, this site is considered eradicated.
2004
July Approximately two acres of giant salvinia were found infesting two private ponds and their associated canals at Delta Plantation. Plants escaped from a nearby ornamental water garden after being purchased from a Savannah nursery. This is the second record of Salvinia molesta in the state and the second occurrence in the Broad-St. Helena drainage. The infestation is located only a few miles east of the Savannah National Wildlife Refuge and is currently undergoing herbicide treatment [S. deKozlowski s.n. (FLAS)].
Texas
1998
May Salvinia molesta first collected in Texas at a schoolyard demonstration pond in Houston [Ronald Jones s.n. (TAES)].
June First found naturalized in Texas at farm ponds near Tomball (R. Jones, pers. comm.). In November, heavy rains washed plants into a local creek.
July Farm pond near Garwood found blanketed with Salvinia molesta.
September Floating giant salvinia was detected at Toledo Bend Reservoir, 186,000 acre impoundment of the Sabine River on the Texas-Louisiana border (J. Hyde, pers. comm.).
November Reports were confirmed of Salvinia molesta in oxbows, canals and tributaries of the Lower Sabine River (C. D'Arbonne, pers. comm.).
December Initial discovery at Swinney Lake, a 13 acre dammed portion of the Swinney Marsh Complex on the Lower Trinity River (K. McDowell, pers. comm.).
1999
March Salvinia molesta recorded at Sheldon Lake State Park, in an old fish hatchery pond.
April August The summer season found new occurrences at impounded creeks and private stock ponds in, including one reaching the north central border, near Flower Mound (C. Owens, pers. comm.). New infestations were in the southeast near Houston, Lovelady, Franklin, Friendswood, Alvin and Mont Belvieu. In Mont Belvieu twin reservoirs encompassing close to 50 infested acres flooded into nearby rice irrigation canals, which themselves drain into Cedar Bayou (R. Helton, pers. comm.).
Late August Salvinia molesta was discovered at Lake Texana, a 11,000 acre impoundment of the Navidad River (L. Hartmann, pers. comm.). The source was traced to a private pond two miles upstream, that had flooded into Sandy Creek, a tributary of the reservoir.
2000
April Thirty-five acres discovered in Lake Conroe, a 21,000 acre impoundment on the West Fork San Jacinto River, just north of Houston.
July Fourth public reservoir impacted by giant salvinia in Texas. Twenty-five acres were identified in Sheldon Reservoir, Sheldon Lake State Park, near Houston.
October Champion Lake, an 800 acre forested impoundment on the west side of the Lower Trinity River and a relatively new acquisition for the USFWS confirmed with Salvinia molesta.
2001
June A new Salvinia molesta occurrence at a private pond in Splendora fills a distribution gap in the salvinia hotspot of southeast Texas. A now contiguous block comprises eleven separate drainage units hosting Salvinia molesta populations.
December Four public reservoirs, six rivers or streams and twenty-five ponds have been confirmed with Salvinia molesta in Texas. This year populations were significantly smaller on Toledo Bend and the other public reservoirs, however herbicide treatment was still necessary. The most concentrated infestation still exist in the Lower Trinity River bottom land, Libery County, Texas, just north of Interstate 10, at the Swinney Marsh area.
2002
September Salvinia molesta appears at a outdoor learning center at League City Intermediate School, Galveston Co. Apparently not introduced with other plants, its origin at the 9 month old pond is unknown (R. Jones, pers. comm.).
2003
March Salvinia molesta discovered in a private pond in Channelview, TX just east of Houston in the Buffalo-San Jacinto drainage. The landowner reports that the plant has been present in her private pond for almost a year, and became suspicious about the identity of the aquatic plant when it began to spread rapidly throughout her pond. S. molesta is presently established and abundant in this new location. (R. Jones, pers.comm.).
October Salvinia molesta was confirmed at a private, 6 acre pond in Center, Texas, approximately 28 km west of Toledo Bend Reservoir. Texas Parks and Wildlife chemically treated the infestation in late October and will monitor the pond over the winter months (H. Elder, pers. comm.). This is the second occurrence of giant salvinia in Shelby County, Texas.
2004
July Giant salvinia appears for a second time in Fort Bend County and in the Lower Brazos drainage. The new infestation in Smithers Lake is approximately 25 miles southeast from the first county occurrence. Smithers Lake, a cooling reservoir for a local power plant, will undergo herbicide treatments (R. Jones, pers. comm.).
Louisiana
1998
July A handful of plants collected at Bayou Teche in Breaux Bridge are suspected to have been carried in on a boat trailer launched at the Breaux Bridge ramp [Martha Griffis (nwrc) # 2830]. The plants were mature, sporocarp bearing and of the mat-forming stage, additional plants were not observed. Surveys and repeated visits failed to located Salvinia molesta in Bayou Teche and the species is not considered as having been established there (C. Dugas, pers. comm.).
September Salvinia molesta first discovered on the Louisiana side of Toledo Bend Reservoir, a 186,000 acre impoundment of the Sabine River on the Texas-Louisiana border.
1999
September Plants escape into canals from a pond at a small diked swamp near Houma [David Rosen 887 (NO)]. Despite continued herbicide efforts this infestation spread by Dec. 2001 to drainage ditches and a crawfish pond on the neighboring wet pasture (C. Dugas, pers. comm.).
2000
October Neighboring private ponds west of Lafayette found infested. Herbicide may have controlled by Nov. 2001.
2001
November Salvinia molesta new to Cameron Parish, at marsh ponds and a canal leading to the ship channel north of Cameron (C. Dugas, pers. comm.). Helicopter survey found the infestation extending 6.5 miles east down the canal and within one half mile north and south of the canal, in marsh ponds.
2003
January December’s storms in southern Louisiana caused extremely high flood conditions that washed Salvinia molesta out of the Cameron Canal and into an extensive marsh system that could easily affect hundreds of acres. 9 Jan.
2004
December Giant salvinia was confirmed in the Jefferson Davis Parish after an alert landowner reported giant salvinia from his farm ponds in Fenton. Louisiana Department of Wildlife and Fisheries found two small ponds blanketed with Salvinia molesta, while the third pond had only a few scattered plants along the shoreline. Although the pathway of the plants is uncertain, officials are deciding among several options for attacking the infestation (C. Dugas and S. Schales, pers. comm.).
Florida
1999
February Positive identification of giant salvinia in a Naples canal followed months of chemically treating a population believed to be Salvinia minima [Jacqueline Smith s.n. (FLAS)]. Salvinia molesta is suspected to have been occurring in the Airport Rd. canal for approximately three years. In September 2000 heavily infested retention and irrigation ponds draining the canal were discovered to be the source of reoccurring plants (J. Smith, pers. comm.).
2000
January Salvinia molesta was found at a 5 acre subdivision pond, also in Naples, where a few plants were spotted just days after being placed there by a resident.
2001
November All Naples sites continue under chemical control measures, no plants observed at this time.
2002
January Salvinia molesta reappears at the Airport Rd. canal in Naples. Plants were found several miles north of previous occurrences but below the junction with the Immokalee Rd. canal (M. Brodie and V. Vandiver, pers. comm.).
2003
June A heavy abundance of Salvinia molesta found again at the Airport Rd. canal, Naples. Plants ranging to the size of a silver dollar grow snagged in alligatorweed (Alternanthera philoxeroides) ¼ mile north of previous occurrences (V. Vandiver, pers. comm.).
2004
June Salvinia molesta discovered in the Golden Gate Canal, Naples (M. Brodie, pers. comm.). This new location is separate from, but just a few miles south of the Airport Road canal, a site where plants have both flourished and diminished for at least five years.
Alabama
1999
March Salvinia molesta identified at a 7 acre golf course pond in Auburn [William Bryant s.n. (UNA)] is suspected to have been occurring since 1997 (M. Masser, pers. comm.).
July Flooding dispersed giant salvinia below the Auburn golf course into two impounded tributaries of Sougahatchee Creek.
August Giant salvinia recorded from a 3.8 acre pond north of Seale.
December Plants carried upslope from the Seale site to a neighbors pond, probably transported by animals such as raccoons or turtles (J. Zolcynski, pers. comm.).
2000
August Plants not found in the 1999 ponds following systemic herbicide treatment.
October Salvinia molesta was discovered at a pond near Montgomery and chemically treated the following day. (J. Jernigan, pers. comm.).
2001
February Salvinia molesta confirmed at an Auburn University pond, again in the Sougahatchee drainage, where plants survived the coldest winter in eight years (W. Moore Jr., pers. comm.).
2002
November Plants have not returned at previously reported, chemically treated ponds in the eastern portion of the state. However, giant salvinia remains following herbicide treatment and scouring rains at the Auburn University pond (J. Jernigan, pers. comm.).
Hawaii
1999
April A rapidly expanding infestation of Salvinia molesta at Enchanted Lake , Kailua, on the island of Oahu (Robert Bourke, Oceanit Laboratories), was feared to threaten the nesting habitat of three endangered water birds, the Hawaiian coot (Fulica alai), the Hawaiian gallinule (Gallinula chloropus sandvicensis) and the Hawaiian stilt (Himantopus mexicanus knudseni). Repeated volunteer efforts to mechanically remove Salvinia molesta from Enchanted Lake appear to have abated the infestation in the freshwater portion of this oligohaline lagoon. By December 2000 the population was substantially reduced.
April Small (<1 acre) infestations also found in 1999 at taro patches and at Lake Wilson, Oahu (Fred Kraus, pers. comm.).
2001
March New occurrences of Salvinia molesta found at streams on Oahu Island. Inaole Stream at Bellow's Airforce Base hosts a population 30 ft. wide and 500 ft. long (M. Anderson, pers. comm.).
August Left untreated, giant salvinia at Lake Wilson, a public reservoir in Wahiawa, has increased substantially to form dense mats extending several meters off the shoreline and rafts in open water.
2003
February A small patch of Salvinia molesta was discovered a few years ago in Lake Wilson and today it completely covers the 300-acre lake. A city-state-federal task force decided this month to try to remove the noxious weed using an amphibious excavator, but so far little progress has been made. Now, the State Department of Agriculture has decided to aid the excavation efforts by applying the herbicide Rodeotm. The herbicide application has begun as officials look for new areas on the lake to continue their excavation efforts. (courtesy of Michael Smart, pers. comm. and photos courtesy Army Corps of Engineers)
May Salvinia molesta continues to cause problems for Hawaii. It has been found in two new locations on the Oahu Island, where Oahu populations are apparently spreading. New localities exist at Kawainui Marsh in Kailua and around a flood control dam at Ho'omaluhia Botanical Garden in Kaneohe. More importantly, giant salvinia has recently been introduced to the big island of Hawaii island where it now occurs at Waiakea Pond in Hilo (M. Wilkinson, pers. comm.).
Mississippi
1999
April Giant salvinia recorded near Moselle [Milton Henderson s.n. (IBE)] at a 1/4 acre spring fed pond and escaped in the ditch below the pond. The water surface had been covered since 1998, a population developing from four plants released by the owner (P. Butler, pers. comm.). The pond has received extensive herbicide treatment.
2003
July MDWFP Fisheries Biologist Tom Holman finds no sign of Salvinia molesta after repeat annual surveys of the pond near Moselle. The site was chemically treated in 1999 and the population is believed to have been eradicated (D. Riecke, pers. comm.).
2004
August Salvinia molesta discovered in Petal, MS, where mature plants are abundant in a 40 + acre marshy bottomland lake system. The area is precariously close to the lower Leaf River and its associated oxbow lakes. Lake system, early 2004 Lake system, summer 2004
Arizona/California
1999
August Salvinia molesta was first observed on the Lower Colorado River at Imperial National Wildlife Refuge, bordering Arizona and California. Thousands of free floating plants were estimated in the river, an occurrence suspected as resulting from water release from a nearby canal (A. Velasco, USFWS memos, 6 & 16 Aug. 1999). A multi-agency survey of the Colorado River and associated backwaters and canals (ranging from Parker Dam to Imperial Dam) delineated the infestation as originating on the California side of the Colorado River, in the Palo Verde Irrigation District Drain (PVID). The PVID system flows into the Old Colorado River channel before entering the Colorado River. The survey found giant salvinia in the Colorado River from the PVID outflow downstream to Imperial Dam (C. Minckley, pers. comm.; Map: Salvinia molesta Survey Results, Bureau of Reclamation, Aug. 1999).
September Public information campaigns proved successful when a resident reports Salvinia molesta from the San Diego River. An 8 ft. diameter patch of giant salvinia was found in a ponded portion of the San Diego River, San Diego County. This infestation was outside of the flow of the seasonal river and was eliminated with herbicides before contaminating the main stream (R. O'Connell, pers. comm.).
2001
November Repetitive herbicide application (as much as 16 times per year) in the Palo Verde Irrigation District Drain in hand with the removal of salt cedar (Tamarix sp.) harboring Salvinia molesta in underbrush, has resulted in markedly decreased numbers of plants along regions of the California drain.
Federal refuges on the Colorado River below the drain have halted herbicide spraying this year. Mats and floating plants continue to persist there.
2003
February Salvinia molesta is continuing its southward spread in the Lower Colorado River. A local citizen and her son found plants this month along the muddy shoreline of the Colorado River near Yuma, AZ. The plants were scattered and occassional; however, they were especially large, fully mature and bore sporocarps.
Georgia
1999
August Edie Creek, a tributary of the Upper Ocmulgee River, holds infestation first noticed at a small farm impoundment.
December Plants had spread downstream to a larger open-ended impoundment along the creek (F. Ellis, pers. comm.). Salvinia molesta found at subdivision ponds north east of Atlanta, also in the Upper Ocmulgee drainage. Below the ponds, a single plant was found in an unnamed tributary of the Yellow River (B. Mauldin, pers. comm.).
2001
November Salvinia molesta not found to persist in Georgia. Although some sites had received herbicide treatment in December 1999, cold winter temperatures are believed to be the real force in this apparent elimination (S. Robinson, pers. comm.).
2003
July Salvinia molesta discovered in the Lower Ogeechee drainage of eastern Georgia in a private pond in Bryan County. The small, spring fed pond was densely covered with a thick layer of plants. GA Department of Natural Resources has already begun to treat the infestation with herbicides. A few plants were also observed below the dam but none were found in a survey of the stream below the infested pond [R. Martin and T. Hendrickx, pers. comm.; Ramon Martin s.n. (FLAS, GA)].
2004
June Salvinia molesta discovered new to the Canoochee drainage, at a 9-acre private pond near Claxton. Georgia DNR believes the giant salvinia was unintentionally introduced with water hyacinth, Eichhornia crassipes, purchased from a Savannah store. The pond is now infested with an abundance of mature plants [T. Will and R. Martin, pers. comm.; T. Will s.n. (FLAS, GA)].
2005
March Giant salvinia, associated with water hyacinth, was found blanketing the surface of a 0.6 acre pond in Macon, Georgia. Georgia DNR found no plants downstream in a recent survey; however they are concerned because the pond drains into Lake Tobesofkee, a 1750 acre recreational reservoir (M. Gray, pers. comm.).
North Carolina
2000
September Salvinia molesta discovered at independent sites in three drainage basins of southeastern North Carolina. Infestations reported by Stratford Kay:
- Northeast of Burgaw, in a swamp slough located 100 yards (30m) from the Northeast Cape Fear River. Flooding from hurricanes in 1999 left plants stranded in trees 12 ft. (3.6m) above ground at this site.
- Jacksonville, scattered in bottomland woods near a creek draining the New River, after heavy rain washed plants from a resident's pond.
- Wilmington, blanketing golf course ponds on the Cape Fear peninsula.
2001
October Populations over wintering and surviving well (D. Patterson, pers. comm.).
2002
May Preparation of voucher specimens by S. Kay documented Salvinia molesta persisting at all three sites in North Carolina (Kay s.n. NCSC; FLAS).
July New site, a private pond in Hubert, Onslow Co., was confirmed and chemically treated.
August Late summer finds Salvinia molesta suddenly spreading well beyond the original slough site and deeper into the swamp near Burgaw, on the Northeast Cape Fear River drainage, Pender Co. (D. Horkavy and S. Kay, pers. comm.).
2003
July A new population of Salvinia molesta was found in a marshy area just 2 miles south of the golf course on the Cape Fear peninsula where plants have been persisting since 2000. North Carolina has decided to tackle all their populations of S. molesta with extensive herbicide treatments. Progress is being made, but NC officials know that this is not going to be an easy task (W. Batten, pers. comm.).
2004
July Salvinia molesta makes its sixth appearance in North Carolina, this time in Sampson County. This discovery marks a new drainage in North Carolina lying adjacent to previous drainages with Salvinia molesta infestations. Plants were found in a small, private pond near Delway where the landowners had placed them after purchasing them from a local garden center a few years back. Giant salvinia now covers almost 25% of the pond and North Carolina officials are working on its eradication (W. Batten, pers. comm.).
Virginia
2004
August Salvinia molesta is new to Virginia, making its first appearance at a private pond in Shenandoah County, near the town of Strasburg. The small, (0.3 acre) spring fed pond is blanketed with Myriophyllum aquaticum (parrot feather) and giant salvinia. Surrounding streams were surveyed for plants that may have escaped the pond, but no plants were found. VA DCR and local volunteers will try to manually remove the plants before resorting to chemical treatment (C. Hutto, pers. comm.).
Contributor Acknowledgments
Authors: C.C. Jacono, M. M. Richerson
Updated: 19 April 2005
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