Biological control of the Australian broadleaved paperbark, melaleuca
The Australian native broadleaved paperbark tree, Melaleuca quinquenervia (Mytaceae), is an invasive weed in the United States, particularly Florida. It was introduced into Florida in the early 1900s as an ornamental tree and to help dry up sections of the Everglades for development. Since then it has greatly expanded its range forming dense monocultures and causing extensive environmental and economic damage. It threatens the Everglades National Park, and its management is a critical part of the Everglades restoration project. It changes the hydrology of landscapes, displaces native vegetation, degrades wildlife habitat, creates fire hazards and causes human health problems.
Melaleuca in Florida, photo courtesy of ABCL
In its native range this tree is widespread along the east coast of Australia from Sydney in New South Wales to Cape York Peninsula in Queensland where it is usually found in swamps, along margins of rivers and in other wetlands. The most extensive stands can be found near the Queensland/New South Wales border.
Since 1986, ABCL has been conducting surveys in Australia to find potential biological control agents of M. quinquenervia. More than 450 insect herbivores have been collected from this tree and its close relatives in the M. leucadendra complex. After host specificity testing by ABCL and USDA-ARS stateside collaborators, four insect species from Australia have been released in Florida: a foliage-feeding weevil, Oxyops vitiosa (1997); a sap-sucking psyllid, Boreioglycaspis melaleucae (2002); a gall fly, Fergusonina turneri (2005); and a gall-forming midge, Lophodiplosis trifida (2008). All agents except F. turneri have established at field sites. Thus far, the weevil has been most effective and together with the other insects is having a dramatic effect on the populations of the paperbark tree. Tree densities have been reduced and flowering has decreased by up to 95% at some sites.
More agents may be required, and ABCL is currently evaluating several new agents including a bud foliage feeding weevil, Haplonyx multicolor, a gall-forming midge, Lophodiplosis trifida, and a gall-forming scale insect, "Sphaerococcus" ferrugineus.
Melaleuca Lophodiplosis indentata, photo courtesy of CSIRO
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