Giant Salvinia (Salvinia molesta) Invades NC
By: Stratford H. Kay, Ph.D., Aquatic Weed Management Specialist,
North Carolina State University
On October 16, 1998, Mr. Steve Hoyle, Aquatic Weed Management
Research Technician in the Department of Crop Science, discovered
an unusually large and robust floating aquatic fern in a water
garden display at the North Carolina State Fair. His description
of the plant made me suspect that it could be giant salvinia.
I reported the incident to Mr. Gene Cross of the North Carolina
Department of Agriculture and Consumer Services (NCDA&CS),
and the following week he visited the display at the fair and
collected samples of the plant in question. The plant subsequently
has been confirmed as Salvinia molesta. The plant was traced
to an aquatic nursery near Beaufort, NC, where it apparently has
been sold as an ornamental for water gardens for the past two
or three years. As of the date of this note, giant salvinia also
has been found in a dealership and one private water garden in
Wilmington and at one nursery and three dealerships in the Raleigh
vicinity. The discovery of this weed has generated considerable
activity within NCDA&CS, including the issuance of several
stop sale notices at the nurseries and dealerships and training
of field personnel to begin a statewide survey of aquatic nurseries
and water garden and aquarium dealerships.
The big question is exactly what does this mean for North Carolina?
There have been no reports yet of its escape into natural areas
anywhere in North Carolina. Available data indicate that Salvinia
molesta is fairly sensitive to cold, but that leaves beneath the
water's surface, as well as the vegetative reproductive bud, would
be protected and could tolerate substantial cold. Information
from the literature indicates that the male sporocarps produces
non-viable spores, hence, the plant is not able to reproduce sexually.
However, this definitely does not preclude entirely that the
possibility for viable spore production may exist in some clones
or ecotypes. Climatic data for the U.S. indicate that the current
location of Salvinia molesta in Toledo Bend Reservoir (northeastern
Texas) is in plant hardiness zone eight. Hardiness zone eight
extends into portions of southeastern and southern North Carolina
and along the Atlantic coastal counties of the state. Based on
this information, it would appear that there is significant potential
for Salvinia molesta to become well established in some areas
of the eastern and southern coastal plain.
This weed has the potential to over-run most of the coastal swamps,
wetlands, and the Carolina bays wherever there may be permanent,
fresh, standing water. Because water hyacinth has overwintered
for several years in the north-central piedmont of North Carolina
and cold tolerance of Salvinia molesta appears to be similar to
that of water hyacinth, I feel that there is significant potential
for it to become established inland, particularly if a mild winter
occurs. This and the fact that it has been sold openly as a water
garden plant increase the potential for this plant to become a
major noxious aquatic weed here in North Carolina in the near
future.
Serious efforts need to be focused on preventing the further spread
of this weed and on eliminating any escaped infestations as soon
as they may be discovered. The discovery of this plant in water
gardens in North Carolina should serve as a signal to other states
in the Southeast and Mid-Atlantic regions to begin a careful review
of what plants are being sold for use in aquariums and ornamental
water gardens. We need to determine the status of this plant
in the ornamental, water garden, and aquarium trade elsewhere
in the South and Southeast. Attention needs to be directed especially
to mail-order sales houses, some of which are openly advertising
a number of plants that are listed as Federal Noxious Weeds or
are included in state noxious weed listings. Any findings of
Salvinia molesta or other noxious weeds should be reported immediately
to the appropriate regulatory agency in your state.
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