Melaleucas in Florida
Having a background in bush regeneration, spending many years pulling weeds out of the Australian bush, I found it strange to hear about Australian natives causing havoc overseas. One such instance is Melaleuca quinquenervia (or paper bark tree) in Florida.
Melaleucas are easily distinguished by the papery bark and spikes of creamy-white to pinkish flowers. The Florida Fish and Wildlife Commission states the trees were introduced into Florida in 1906 as a potential commercial timber and later extensively sold as a landscape ornamental tree and windbreak. It was also planted to dry up the Everglades to decrease mosquito populations and allow for development.
Melaleuca trees posess the qualities that most weeds exhibit which is to grow quickly even out of its natural geographic range where there are no natural predators to keep its numbers under control. This means it does grows well in disturbed wet pine flatwoods, marshes and swamps, so the Everglades provide perfect conditions for the tree to grow, where it is nonnative tree is rapidly displacing native cypress and sawgrass in the Everglades.
The Florida Fish and Widlife Commission regards the managment of Melaleuca as important as it forms dense stands, preventing native plants from growing that are important to wildlife. In the Everglades, melaleuca trees form nearly monospecific forests in formerly treeless sawgrass marshes, disrupting historical water flows. Melaleuca forests also pose a serious fire hazard to surrounding developed areas because of the oils contained within the leaves that create hot crown fires.
According to the University of Florida, there have been three different methods to control the tree which are biological, mechanical and chemical control. For Biological control, three insects were released as biological control agents: the melaleuca weevil (Oxyops vitiosa) released in 1997, the melaleuca psyllid (Boreioglycaspis melaleucae) released in 2002, and the melaleuca stem-gall midge (Lophodiplosis trifida) released in 2008. Although none of these insects will kill mature melaleuca trees, they can significantly reduce tree growth, seed production, and seedling establishment.
Mechanical controls includes heavy machinery such as logging equipment, mowing equipment, and mulchers are sometimes used for melaleuca removal. This method is usually used during land clearing for development and for removal along canals, and roadsides. Mechanical removal is not widely used for melaleuca control in natural areas as it is expensive and generally causes considerable soil disturbance.
Herbicides can be used for killing individuals or large populations of melaleuca trees. To control large, dense stands of mature melaleuca trees, state and federal agencies have applied herbicides by helicopter with the active ingredients glyphosate and imazapyr. To control individual trees, Glyphosate and imazapyr are also applied with handheld equipment to control seedling and sapling trees.
So it appears while the species of plant is different, many countries have the same issue of controlling invasive pests. Even the same methods that are used in bush regeneration in Australia, seem to be used in controlling melaleuca quinquenervia trees in Florida.
Melaleuca bark