Stratford H. Kay
Associate Professor
Crop
Science Department
North Carolina State University
October 2, 2000
Giant salvinia (Salvinia
molesta) first appeared in North Carolina in October 1998 at an
aquatic nursery display at the State Fair. This highly invasive, floating
aquatic
plant subsequently was found in wetland nurseries, water garden dealerships,
and ornamental pools in 19 NC counties, but was not known to exist outside
of cultivation until this summer. Following a tip received in August, 2000
from a commercial aquatic applicator, this weed was found in several ponds
on a golf course in Brunswick Co. In September, 2000 the weed was reported
in two ponds on another golf course at Wilmington. The identity of the weed
at these sites was confirmed by personnel from the North Carolina Department
of Agriculture and Consumer Services (NCDA&CS) and North Carolina State
University (NCSU).
During a pond management workshop
on September 20, 2000 in Kinston, a property owner brought in a live sample
of giant salvinia from a pond in Jacksonville, and another aquatic applicator
reported a large infestation in a swamp pond within a subdivision adjacent
to the Northeast Cape Fear River east of Burgaw. Thursday, September 28,
2000, a joint task force of personnel from NCSU, NCDA&CS, the North Carolina
Department of Environment and Natural Resources Division of Water Resources,
the Cooperative Extension Service office at Wilmington, and the U.S. Army
Corps of Engineers, Wilmington District, visited the sites at Wilmington,
Jacksonville, and near Burgaw. Both ponds at the golf course in Wilmington
were completely covered with giant salvinia, and small patches of plants were
present in a drainage ditch into which the lower pond flowed. Data collected
using GPS equipment indicated that the upper and lower ponds were about 0.25
and 0.5 acres, respectively, and the ditch was 0.1 acre. Both ponds had been
infested for more than two years. The
site in Jacksonville was of much higher concern as flooding two weeks earlier
had washed large masses of giant salvinia from a small pond (0.25 acre) into
the adjacent wetland, which flows into Northeast Creek. Very little salvinia
remained in the pond. A survey of the wetland revealed large mounds of plants
piled against the tree line and smaller patches of live plants on wet soil
up to 100 yards from the pond. A few plants were found within 25 ft. of the
creek in the wetland. Giant salvinia has been in this site since 1999. No
plants were found downstream at this time, but there is concern that flooding
in the fall of 1999 and mid-September 2000 may have washed plants into Northeast
Creek and the adjacent wetlands downstream.
The site currently of greatest concern
is the swamp pond beside the NE Cape Fear River. Property owners here indicated
that this weed has been present for at least three or four years. Giant salvinia
is present in the open water that encircles a swampy wetland. Plants were
visible well back into the trees in the wetland and in a small drainage canal
paralleling the road just east of this site. Some waterhyacinths also were
seen in the canal. The pond, including the encircled wetland, occupies 15
acres, and has been flooded several times. In fall 1999, ten to twelve ft.
of water covered the road next to the pond. Dead salvinia was found hanging
in trees ten to twelve ft. above the ground, where they were stranded during
the flooding following Hurricane Floyd in 1999. This site is only 100 ft.
from the Northeast Cape Fear River, and stranded plants were found in trees
within 30 ft. of the river. It is highly probable that giant salvinia has
been distributed widely downstream into the swamps along the river. Control
of giant salvinia in sites such as this is essentially impossible due to obstructions
preventing herbicide treatment. Surveys of adjacent wetlands will be conducted
during the next two weeks by NCDA&CS. Updates will follow pending the
findings of this survey.