|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