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Title: From Invasive to Fixed-in-Place: the Transformation of Melaleuca quinquenervia in Florida

Author
item Tipping, Philip
item Pratt, Paul
item Center, Ted

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2007
Publication Date: 1/8/2008
Citation: Tipping, P.W., Pratt, P.D., Center, T.D. 2008. From Invasive to Fixed-in-Place: the Transformation of Melaleuca quinquenervia in Florida. International Symposium on Biological Control of Weeds. 642.

Interpretive Summary: Melaleuca quinquenervia once spread unimpeded across the south Florida landscape. The complete lack of top down regulation of its growth and reproduction resulted in its rapid spread into pine flatwoods, cypress domes, sawgrass prairies, and hardwood hammocks. Recruited seedlings reached reproductive maturity as soon as two years and were promoted further by natural perturbations such as fires which caused more seed releases and disproportionately damaged native plant species. The inevitable outcomes were landscape level melaleuca monocultures with huge canopy held seedbanks with tremendous reproductive potential. At its height Melaleuca infested about 0.61 million ha throughout Florida. Recognition of the problem prompted large scale chemical and mechanical control efforts starting in the 1990’s which checked the expansion of these infestations on public lands. The first biological agent, Oxyops vitiosa, was introduced in 1997 and the second, Borelioglycaspis melaleucae, in 2001. These natural enemies, especially O. vitiosa, have transformed both the habit and reproductive capacity of melaleuca to a point where the essential nature of the problem has been redefined. It is now clear that the capacity of melaleuca to invade and dominate new habitats has been severely constrained by biological control. Currently, new organisms are under development to target melaleuca populations in continuously flooded habitats which have been less impacted by the current agents.

Technical Abstract: Melaleuca quinquenervia (melaleuca) once spread unimpeded across the south Florida landscape, infesting 0.61 million ha at its height. The complete lack of top down regulation of its growth and reproduction resulted in its rapid spread into pine flatwoods, cypress domes, sawgrass prairies, and hardwood hammocks. The first biological agent, Oxyops vitiosa, was introduced in 1997 and the second, Borelioglycaspis melaleucae, in 2002. These natural enemies, especially O. vitiosa, have transformed both the habit and reproductive capacity of melaleuca. Plants attacked by O. vitiosa grow slower (9.1 cm yr-1 vs 96.1 cm yr-1); produce many more tips (4.2 tips cm height-1 vs 2.8 tips cm height-1) resulting in a shorter, bushier plant; produce fewer seed capsules (0.006 capsule clusters cm tree height-1 vs 0.343 capsule clusters cm tree height-1), resulting in 97.5% less seed per tree. Existing tree densities have declined 35.4% since 2002 when not protected from these natural enemies while protected areas increased by 9.4%. In another study, melaleuca was able to recruit only 2.4% of its previous density of seedlings/saplings. It is now clear that the capacity of melaleuca to invade and dominate new habitats has been severely constrained by biological control.