Will a Weevil From Down Under Find Melaleuca Finger-Lickin' Good?
| OCHOPEE, FLA.
Hiking through the Big Cypress National Preserve here, a member of the local native plant society gives a shout and tears out a sapling by its roots. "Melaleuca!" she exclaims derisively.
None of the group recoils in horror from this act of apparently bad environmental manners. Melaleuca is known in Florida as the scourge of the Everglades, a tree considered so offensive that it has been declared a Federal Noxious Weed.
To the untrained eye, a melaleuca tree in the saw grass doesn't set off alarm bells. Nor do the canals slicing through the south Florida peninsula. Yet both are part of the devastating changes made to the natural ecosystems here that have suffered from human intervention.
Called the broadleaf paperbark tree in its native Australia, Melaleuca quinquenervia was brought to Miami in 1906 as an ornamental landscape tree. With its eye-catching, flaky white bark and fuzzy, pointed leaves, the tree didn't seem pernicious.
But melaleuca has gone awry, increasing exponentially through the last great wetlands of south Florida, replacing the unique subtropical vegetation of the tree islands and encroaching upon the saw grass prairies. It has no natural enemies here. Yet.
Scientists from the United States Department of Agriculture (USDA) are awaiting approval to introduce oxyops vitiosa, a weevil that is one of the melaleuca's main enemies in Australia.
"It's still in the process," says Gary Buckingham, a research entomologist for the USDA in Gainesville, Fla. "The petition is being evaluated by various agencies who check for safety to make sure that everything is OK for release."
A grayish brown bug with a snout, the weevil feeds on new leaf growth of the melaleuca and, ideally, will stem the tree's stubborn tide. Its larvae feed on the new leaves of both mature melaleuca trees and seedlings. "It's one of the safest biological controls I've seen," says Ted Center, project leader of weevil research for the USDA.
"It's really a plant that restricts what will feed on it," says Mike Bodle, an aquatic biologist for the South Florida Water Management District. who describes melaleuca as "rancid, oily, and volatile." Mr. Bodle says the weevils are "melaleuca addicts" and, in tests, have not taken to important south Florida crops trees like citrus or mango - or any other plants, for that matter.
Planted as windbreaks and to stabilize the banks of the canals, melaleuca has asserted itself all over the region from Lake Okeechobee south, including the Everglades. It blooms up to five times a year, and saplings can survive under water for months.
A persistent, hardy tree, melaleuca has completely adapted to the Everglades' extreme conditions of flood and drought. Instead of slowing down melaleuca's rampant growth, stresses like fire, drought, frost, and wind breakage cause each tree to release about two million seeds. So far, the tree has taken over half a million of the region's 7.5 million acres.
The tree forms dense forests that crowd out native wildlife habitat like cypress trees and saw grass. In the early 1980s, the melaleuca infestation reached crisis proportions.
"It's difficult to understate the problems this plant is creating in terms of its disruption of natural areas," says Doug DeVries, a supervisory biological technician at Everglades National Park. "In the world of ecology, diversity and richness in plant species is a strong measure of wildlife habitat value."
Unlike Melaleuca alternafolia, whose oil is used for a myriad of products from lotions to vitamins, M. quinquenervia is not considered a valuable tree. It has been used on a limited basis as garden mulch and boiler fuel for sugar refineries. Most "harvesting," however, falls under the label of eradication.
Current removal techniques have proved to be labor-intensive, expensive, and slow. Crews in federal land management areas like Big Cypress National Preserve and Everglades National Park are transported by helicopter to remote infested sites, where they cut down the trees and kill the stumps with herbicide.
Because manual efforts to control melaleuca can't keep up with its rapid growth, the USDA has been studying the weevil for the past eight years along with others of the 100-odd insects that prey on melaleuca in Australia.
"We know we need another biological control to attack the flowers," says Sue Jewell, senior biologist at Loxahatchee National Wildlife Refuge, where stands of melaleuca are a big problem. "It might be enough with two different insects."
Biocontrols have precedents in south Florida. The South American alligator weed has diminished since a biocontrol insect was released in the '80s, and other exotic pest plants - water hyacinth, hydrilla, and water lettuce are also under biological control. "Establishment is the most difficult and sensitive part," Mr. Bodle says. How successfully the weevil spreads will determine the effect it has on the tree.
Scientists want to get started with the weevil. "Based on the data I've seen, it should already have been released," says Mr. DeVries. "It takes several years for a control to build up a population of sufficient size to have an impact."
Craig Johnson of the US Fish and Wildlife Service concurs. "It's time to do the field tests and see how it works in the real environment. We're ready to do the monitoring." Those involved with Everglades restoration hope that nature's balance, in form of a bug from Down Under, will solve what millions of dollars of human and machine labor could not.