Psyllid and Weevil: Dynamic Duo
Tipping and co-investigator Paul D. Pratt, an ARS entomologist at Fort
Lauderdale, expect the psyllid to complement the efforts of another
weed warrior, the melaleuca leaf weevil, Oxyops vitiosa. The
ARS and Australian scientists pioneered use of this grey-brown, quarter-inch-long
weevil to fight melaleuca in North America.
The hard-working weevil's historic U.S. launch in 1997 capped more
than a decade of scrutiny by the scientists. "The weevil's outdoor
introduction here," Tipping says, "started with our release
of 1,600 at 13 melaleuca-infested sites in south Florida." Today,
millions of the snout-nosed weevils are merrily munching on melaleuca
throughout the Everglades and South Florida.
Eating the silvery leaves of melaleuca saplings "is what this
busy weevil does best," points out Ted D. Center, research leader
at Fort Lauderdale. "Losing leaves stresses melaleuca. That means
the trees don't put as many resources into producing seeds as they would
if they weren't being bothered."
But the weevil most definitely bothers melaleuca. The effects have
been especially noticeable along Florida's west coastfrom Fort
Myers to Naples. There, conditions for the weevil are good. The weather
is dry, soils are sandy, and melaleuca stumps profusely produce what
the weevils like to feast on mostfresh, young foliage. All these
factors favor the Aussie insect's reproduction.
Weevil Thrives at West Coast Sites
The best results have occurred at two locations: first, a cut-over
pasture close to Estero Bay Aquatic Preserve outside Fort Myers and
second, clearings at Picayune Strand State Forest in Naples. Melaleuca
stumps at both locales have sprouted succulent new leaves. The weevil
has reproduced in large numbers and, as a result, has had a greater
impact at the Preserve and the Forest than at any of the other original
release sites.
In contrast, the east coast of South Florida has not had quite the
same fortune. In particular, at the Loxahatchee National Wildlife Refuge
in Boynton Beach, the weevil has not fared well. The refuge doesn't
offer the expanses of dry ground that the weevil needs during at least
part of the year to complete its life cycle. "But wet soils aren't
a problem for the psyllid," explains Pratt, "so the psyllid
should add to the effects of the weevil."
Now, with the help of AmeriCorps internsand funds from the Florida
Department of Environmental Protection and the Dade County Department
of Environmental Resource ManagementARS scientists are moving
the helpful weevils from areas where they have reproduced the most to
other areas where they might also flourish. So far, the scientists and
interns have relocated a total of over 500,000 of the six-legged biocontrol
agents to a half-dozen venues.
"Our goal was to use the weevils to minimize the number of seeds
that melaleuca produces. That, in turn, would limit the spread of this
invasive tree," emphasizes Center. "We are impressed! The
weevils are attacking melaleuca everywhere they find it. And we're crediting
the weevils with cutting melaleuca seed production by 50 to 90 percent."By
Marcia Wood
and Alfredo
Flores, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS
National Program (#304) described on the World Wide Web at http://www.nps.ars.usda.gov.
John A. Goolsby
is with the USDA-ARS Australian
Biological Control Laboratory, 120 Meiers Rd., Indooroopilly, Queensland,
Australia 4068; phone 61-7-3214-2821, fax 61-7-3214-2815.
Gary R. Buckingham
is with the USDA-ARS Invasive Plant Research Laboratory, P.O. Box 147100,
Gainesville, FL 32614; phone (352) 372-3505, fax (352) 955-2301.
Philip W. Tipping,
Paul D. Pratt, and Ted
D. Center are with the USDA-ARS Invasive
Plant Research Laboratory, 3205 College Ave., Fort Lauderdale, FL
33314; phone (954) 475-0541, fax (954) 476-9169.
"Sap-Sucking Psyllid Pesters Pushy Plant" was published
in the November
2002 issue of Agricultural Research magazine.
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