
Leaf-Weevil Proves Successful
Against MelaleucaBy Jesús
García April 28, 2000After being released two years ago by
Agricultural Research Servicescientists, the leaf-weevil Oxyops vitiosa is proving highly effective
at defoliating existing stands of melaleuca saplings and will likely prevent
further spread of this invasive tree. Melaleucaquinquenervia, or broad-leaved paperbark tree,
naturally inhabits areas along the east coast of Australia from the northern
tip of Queensland and parts of Papua New Guinea down to Sydney in New South
Wales. In these areas, the tree is held in check as part of a balanced
environment. This fast-growing tree was imported into Florida in the late 19th century.
Later, it was planted as a way to drain the Everglades and now infests nearly
500,000 acres of wetlands. The tree is widely considered to be transforming the
Everglades from a wet prairie to a closed-canopy swamp forest. Estimates of
annual losses range as high as $168 million. Researchers with ARS
Aquatic
Plant Research Unit in Ft. Lauderdale, Fla., led by entomologist Ted
Center, have sought alternatives to the traditional forms of melaleuca control:
felling of mature trees, removal of saplings by hand, burning, and herbicides.
Infestation is likely to recur after use of these techniques unless follow-up
eradication measures are employed. Biological control is being used to
complement these methods. After extensive testing of the 6- to 9-millimeter-long native Australian
leaf-weevil and its larvae--for more than a decade by ARS scientists in
Australia and Florida--more than 1,550 adult weevils and 6,700 larvae were
released at 13 sites in six counties between the spring of 1997 and June 1998.
ARS researchers have recently found that those populations are now well
established, increasing and beginning to disperse to other infested areas. Every year each melaleuca tree naturally loses 25 to 33 percent of its
leaves. But the leaf-weevil is so proficient at consuming any new leaves that
over time some trees could become completely defoliated. Some are already
exhibiting tip die-back. Ultimately, the weevil will alleviate one of the
biggest problems associated with controlling melaleuca--its ability to disperse
millions of seeds when it dies. Scientific contact: Ted
D. Center, ARS U.S. Aquatic Plant Research Unit, Ft. Lauderdale, Fla.;
phone (954) 475-0541, fax (954) 476-9169, [email protected]. U.S. Department of Agriculture |