Giant Salvinia Attacked by Tiny
Weevil By Marcia
December 18, 2001
A fern with a reputation as one of the worlds worst
aquatic weeds is showing up in ponds, lakes and reservoirs from North Carolina
to Hawaii. When conditions are right, giant salvinia--Salvinia
molesta--forms dense mats that can double in a few days.
Sometimes more than 2 feet thick, the mats block out sunlight
that other plants need and use up oxygen that fish, insects and other aquatic
dwellers require. The weed also ruins conditions for fishing, boating and
waterskiing and clogs irrigation and electrical generating systems.
Service scientists in the United States and Australia are working to stop
this pest. Researchers based at ARS laboratories in Fort Lauderdale, Fla., and
in the Brisbane suburb of Indooroopilly, Australia, are leading new studies of
the genetic makeup and appetite of a tiny, salvinia-eating weevil.
The object of their attention is a dark-colored,
one-tenth-inch-long weevil known as Cyrtobagous salviniae, obtained from
another salvinia species, Salvinia minima, or common salvinia, that
grows in Florida.
The C. salviniae weevil has earned kudos internationally
for holding salvinia in check, according to Ted D. Center, director of the
Invasive Plant Research Laboratory in Fort Lauderdale and Gainesville. The
helpful insect has already been used--with great success--in more than 13
Philip W. Tipping and other researchers at the Fort Lauderdale
lab have collected more than 800 salvinia weevils from common salvinia in
Florida. They turned the weevils loose in an east Texas pond and lake and in a
reservoir on the Texas-Louisiana border.
The scientists have begun to make additional releases. For this
work, however, they are using weevils collected from Australia rather than from
Florida. In Australia, the weevils provided dramatic and rapid results in
battling salvinia. The weevils that the researchers have set free at
salvinia-infested sites are descendants of weevils collected by the team that
ARS colleague John A. Goolsby leads in
ARS researchers are the first in the United States to use an
insect to attack salvinia.
ARS is the U.S. Department of
Agricultures chief scientific research agency.