Biological control of melaleuca
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The biological control method uses the tree's natural enemies to keep the trees in check. Two biological control agents, both insects, are currently at work on melaleuca, and they are particularly fond of young seedlings and new leaves. Feeding damage from these two insects is reducing melaleuca reproduction and seedling establishment. You can order biological control insects to release on your property at http://kgioeli.ifas.ufl.edu/biocontrolorder.htm.
Two biological agents has been released thus far. They are the melaleuca weevil (Oxyops vitiosa) and the melaleuca psyllid (Boreioglycaspis melaleucae). Two more agents, the melaleuca bud-gall fly (Fergusonina turneri) and the stem-gall fly (Lophodiplosis trifida) are being planned for future release.
The melaleuca weevil was released in 1997. It has been successful in establishing itself, dispersing from the release site, and eating melaleuca. The larvae feed only on new leaf (young) tissue. Adults prefer new leaves, but will eat mature leaves. One shortcoming of this particular insect is that it requires dry soil for the larvae to pupate. Melaleuca commonly occurs in standing water, and the weevils cannot complete its life cycle from these particular trees.
The young scrape off the living plant tisse from the leaves, and leave behind the waxy cuticle--these look little "windows" on the leaves. Evidence from adult weevils are the oval-shaped holes in the leaves.
The melaleuca psyllid was released in 2002. It has not yet spread across South Florida, but it is well-established and dispersing from its initial release sites. In the areas where it has established, the psyllid has been may be having a greater impact on melaleuca trees than the weevil--to the point of killing small trees.
Immature psyllids are readily detected due to the presence of floculence--a white, waxy substance secreted by the larvae that may deter attacks from predators. Adult psyllids are very small (about the size of a gnat). Besides some death of small trees, the psyllids are reducing flowering and seed production, thinning the tree canopy, and stunting tree growth.
The melaleuca bud-gall fly is being released this year ( 2005 ). This particular insect produces galls on melaleuca stems that preempts flower and seed production. For more information on this species, read the March 2004 issue of Offshoots.
The stem gall-fly is still undergoing host-specificity testing (ensuring it will only eat melaleuca) in Gainesville, FL. No release dates are yet projected.
For pictures of these insects, check out the photo gallery.
