Giant salvinia damaged by Cyrtobagous salviniae,
a weevil whose larvae are extremely effective biocontrol agents against this
water weed. Click the image for more information about it.
story to find out more.
Weevil Wreaks Havoc on Giant
Salvinia By Alfredo Flores
September 7, 2004
Giant salvinia, a free-floating invasive fern sometimes referred
to as one of the worlds worst water weeds, may have met its match, thanks
to the efforts of Agricultural Research Service (ARS) scientists.
In lakes and ponds in Texas and Louisiana, two-foot-thick mats
of giant salvinia, known scientifically as Salvinia molesta, block out
sunlight and use up oxygen, making it hard for some forms of aquatic life to
survive beneath them. Notorious for its presence in slow-moving, quiet,
freshwater systems, its rapid growth and tolerance to environmental stress make
it an aggressive, competitive species. It can quickly take over aquatic
environments, restricting water use and harming local economies dependent on
recreational activities like fishing and waterfowl hunting.
ARS scientists at the
Plant Research Laboratory in Fort Lauderdale, Fla.led by entomologist
Phillip W. Tipping and center director Ted D. Centerhave been getting
good results from releasing a diminutive weevil, Cyrtobagous salviniae,
that loves to consume salvinia. Just one-tenth-inch long, this dark-colored,
long-nosed biological control agent is proving itself effective against S.
The adult female weevil lays her eggs in cavities she creates by
chewing into salvinias rootlike structures, or rhizomes, and the petioles
that attach the leaves to the rhizomes. The larvae that hatch feed on flower
buds before tunneling into the rhizomes, where they inflict the most serious
damage. Interestingly, this highly specific insect feeds only on salvinia of
South American origin, rejecting other closely related salvinia species from
Africa and Europe.
Weevils from Brazil were released in October 2001 at sites in
Texas and Louisiana. Within two years, the salvinia mats almost completely
collapsed, and water bodies formerly choked by the weed are now mostly open
water. As the giant salvinia infestations have declined, so have the
populations of the weevil, thereby striking a balance between the two. The end
result is a permanent suppression of a fearsome weed into an almost
unnoticeable background plant.
about this research in the September 2004 issue of Agricultural Research
ARS is the U.S. Department of
Agricultures chief scientific research agency.