Melaleuca Management in Florida
The
South Florida Water Management District's Vegetation Management
Program is responsible for managing invasive plants in 16 counties
in central and southern Florida, an area of 15,673 square miles.
The District manages non-native invasive aquatic and upland plants
in more than 1,800 miles of canals and levees, 500,000 surface acres
of public lakes, over 850,000 acres of Everglades Water Conservation
Areas, and on 250,000 acres of public conservation lands.
Thanks to a $30 million, 15-year effort coordinated by the South Florida Water Management District's Vegetation Management Program and several other state and federal agencies, the number of acres of land covered by the Australian melaleuca tree (Melaleuca quinquenervia) in South Florida has declined by over a third. In 1993, 52 percent of all melaleuca in South Florida was found on public conservation 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 (USDA) began introducing insects in South Florida (only
after they were rigorously screened in quarantine) that can only
feed on melaleuca trees beginning in 1997 to help slow the spread of
new seedlings and saplings. More Australian insects are
now in the quarantine pipeline.
Melaleuca's rapid, aggressive expansion during the first part of the
20th Century altered thousands of
acres in the Everglades by replacing native sawgrass marshes, wet
prairies, and aquatic sloughs with a non-native novel habitat or "a
forest where a forest never existed before." Mature melaleuca trees commonly form very dense stands that virtually
exclude all other native plant species, especially in disturbed
areas. Their growth pattern also allows wildfires to spread
more quickly and at a higher temperature causing higher adjacent
native tree mortality than native plant fires.
Melaleuca trees flowers up to five times per year and any damage to
the tree that cuts water flow to the stems containing seed capsules
(left photo),
such as fires and freezes, will result in seed release. Seeds can
remain viable for 10 years and a single tree can store 2-20 million
seeds.
Because
of this, 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 ones already released, will provide the best
and cheapest long-term solution to the overall problem. They also
will allow other technologies to be redirected toward controlling
South Florida's many other invasive plants.
Melaleuca distribution 1993
"Hack and squirt" herbicide treatment of melaleuca
Fact Sheets and other
Information about Melaleuca in Florida
Melaleuca (Melaleuca quinquenervia)
DEP Weed Alert
[PDF 284 K]
Melaleuca
Management Plan for Florida [PDF
2.6 MB]
Draft invasive
species chapter of the 2006 South Florida Environmental Report now
available
[PDF 2.5 MB]
Links
Ecological Consequences of Invasion by Melaleuca Quinquenervia
in South Florida Wetlands: Paradise Damaged, not Lost
- University of Florida IFAS