Artificial Diet for Melaleuca Biological Control Agent

Agricultural Research Service scientists have developed a new technique for rearing an Australian weevil that feeds on a weed-like tree now threatening the Florida Everglades.

The tree, called melaleuca, was imported in the late 19th century to help drain the Everglades for agriculture and residential development. Now Melaleuca quinquenervia- -or broad-leafed paperbark tree--infests nearly 500,000 acres of Florida’s wetlands. The tree is so invasive it’s threatening the ecological balance of the Everglades and costs as much as $168 million in annual losses to the local economy.

ARS scientists with the Invasive Plant Research Laboratory in Ft. Lauderdale, Fla., led by entomologist Gregory S. Wheeler, have developed a technique--including an artificial diet--for mass rearing Oxyops vitiosa. This 6- to 9-millimeters-long native Australian leaf weevil has potential as a biological control for melaleuca. In Florida, where it was released in 1997 and 1998 for field trials, O. vitiosa has proved very effective in defoliating existing melaleuca stands and preventing massive seed drops, thus curbing the weed’s spread.

Several diets were tested before researchers found just the right combination of ingredients--including sucrose, glucose, cornstarch, vitamins and minerals--to ensure the weevils’ survival from egg hatch through pupal stage.

Rearing the weevil to its larval stage did not require special conditions. But for the larvae to grow adequately, a substrate had to be developed on which it could develop to its next stage, or pupate. ARS researchers found that a medium consisting of sand, water and an absorbent material like crushed floral foam or peat moss worked best. This composition retains enough moisture and allows for the amount of air exchange necessary for proper pupal development.

O. vitiosa is becoming well established and increasing its range. The artificial-diet-reared weevils have already been released in melaleuca-infested sites throughout south Florida and seem to be performing well.

ARS is the U.S. Department of Agriculture’s principal scientific research agency.

Scientific contact: Gregory S. Wheeler, ARS Invasive Plant Research Laboratory, Ft. Lauderdale, Fla.; phone (954) 475-0541, fax (954) 476-9169, wheelerg@saa.ars.usda.gov