Invasive Exotic Plants

Melaleuca Acreage Down by a Third in Past Decade in South Florida; Credit Goes to Interagency Efforts

MelaleucaThanks to a $25 million, 10-year effort coordinated by several state and federal  agencies, the number of acres of land covered by melaleuca in South Florida has declined by nearly a third.

The recently released "Melaleuca Management Plan: 10 Years of Successful Melaleuca Management in South Florida, 1988-1998" contains this information  plus recommendations from the interagency Melaleuca Task Force. The report was  published by the Florida Exotic Pest Plant Council and edited by Francois B. Laroche, a senior environmental scientist at the South Florida Water Management District.

In 1993, 52 percent of all melaleuca in South Florida was found on public land (252,008 acres), while 48 percent was on private land. Four years later, in 1997, 35 percent of all live melaleuca in South Florida was found on public land (137,181 acres) and 65 percent on private land. A combination of biological, chemical, mechanical, and physical control methods is directly responsible for this reduction.

The most well known feature of this management program has been the introduction  of "biological control agents," or insects, from Australia. Melaleuca spread so quickly in South Florida after its introduction 100 years ago because it had no known natural enemies. In Australia, insects helped keep melaleuca growth in check. The U.S.  Department of Agriculture introduced one of these insects, the snout-nosed beetle, in 1997 in South Florida after a successful eight-year quarantine program (including two years for federal approvals). The beetle already is slowing the spread of new seedlings. More Australian insects are now in the quarantine pipeline.

However, chemical herbicides currently are the most effective technique available for the short term, and large areas of trees can be treated at a reasonable cost. If the other insects are successful as expected, they and the snout-nosed beetle will provide the best and cheapest long-term solution to the overall problem. They also will allow other technologies to be redirected toward eradicating South Florida's many invasive plants.

"We could not have done much of this work without the continued support of the melaleuca eradication program by Congress and the Florida Legislature," said Frank Finch, District executive director. "We also thank all the agencies involved in the task force for their support of eradication on public lands."

Melaleuca's rapid, aggressive expansion has altered thousands of acres in the Everglades by replacing native tree islands, sawgrass marshes, wet prairies, and aquatic sloughs. Mature melaleuca trees commonly form dense stands that virtually crowd out all other native plant and animal species, especially in disturbed areas.  Their growth pattern also allows wildfires to spread more quickly and at a higher temperature.

The Melaleuca Task Force says the uncontrolled expansion of the trees is one of the most serious ecological threats to the biological integrity of South Florida's natural systems. The District created the task force in 1990 in cooperation with the Florida Exotic Pest Plant Council. The group published its first "melaleuca management plan" that year. This current plan, the third edition, includes the technological advances and operational progress that have occurred in the past 10 years.

The task force includes scientists from the Florida Department of Environmental Protection; National Park Service; U.S. Army Corps of Engineers; USDA; U.S. Fish and Wildlife Service; Miami-Dade, Lee, and Palm Beach counties; the University of Florida; the University of Miami; and the District.

The 1999 plan includes the following recommendations:

  1. securing money to import more insects for testing and to build and staff a permanent quarantine facility
  2. continuing control on public lands and increasing focus on other areas needing more melaleuca eradication
  3. using the support of Exotic Pest Plant Council to lobby the state Legislature and Congress to provide more money and enact more laws to manage melaleuca and other pest plants.

In the past eight years, the District budgeted $14,277,794 to fight melaleuca infestations. Approximately 58 percent, or $8,312,794, came from other sources besides District ad valorem funds. These include Florida Power & Light Co. mitigation funds, Surface Water Improvement and Management funds, the Corps,  and a DEP cost-sharing program that provided approximately $5.5 million. SWIM and Corps money is for Lake Okeechobee melaleuca eradication only. At the current level of funding, melaleuca could be eliminated from the water conservation areas and Lake Okeechobee within the next five to 10 years.