Reuniting Melaleuca with its Natural EnemiesMelaleuca (MEL-ah-LUKE-ah) is a noxious weed that invades precious natural areas inFlorida, including the Everglades. It was brought from Australia in the early 1900s for use inlandscaping and development, but the hundreds of natural enemies, including insects anddiseases, that feed on it in its native home were left behind. Without natural enemies inFlorida, melaleuca grows and spreads unchecked, easily outcompeting native vegetation.Because of the threat melaleuca poses to natural areas, it has been placed on the Federaland State Noxious Weed Lists and is now illegal to possess in Florida. For more than adecade, land managers have been fighting this invasive tree with mechanical and herbicidaltreatments. Melaleuca’s natural enemies could provide another treatment option, one that isbiologically based and self-sustaining.

For more information on melaleuca and its management, visit the TAME Melaleuca Web site

http://tame.ifas.ufl.edu

Project Coordinator: Cressida SilversUSDA-ARS Invasive Plant Research Laboratory

Ft. Lauderdale, FL(954) 475-0541

USDA-ARS is an equal opportunity employer. February 2004

Natural Enemiesof Melaleuca

http://tame.ifas.ufl.edu

Enemies2 2/6/04 3:49 PM Page 1

The Invader: MelaleucaWhen melaleuca was introduced outside its nativerange the tree was separated from its coevolvednatural enemies (e.g. predators, parasites, andpathogens). Consequently, it was released fromthe constraints that would otherwise limit its popu-lation. Since its arrival in the U.S. 100 years ago,melaleuca has covered hundreds of thousands ofacres in South Florida.

The Mission: Biological ControlA successfulmethod ofmounting acounterstrike atan invasivespecies is torelease its natural enemieswhere theinvader is foundoutside its homerange. This solution, known

as biological control, does not eradicate the pest,but is intended to decrease populations. Since thesearch for potential biological control agents beganin 1986, over 450 potential agents from Australiahave been examined. Agents approved for releasemust only feed on melaleuca and not harm otherplants or animals. For the melaleuca problem inFlorida, researchers wanted species that wouldfeed on new growth and reduce seed production.Two insects passed the tests and were released todo their work.

State and federal agencies including the SouthFlorida Water Management District, Florida’sDepartment of Environmental Protection, and theUSDA’s Agricultural Research Service cooperatedto release the two biological control agentsdescribed here. While these beneficial insects arenow feeding on melaleuca trees across southernFlorida, it may take several years for them to reachtheir full impact, and it may require additionalagents to keep melaleuca manageable.

U.S. Secretary of the Interior GaleNorton releases psyllids onto amelaleuca tree during the first psyllidrelease event in April 2002.

Agent Number 1: The Melaleuca WeevilScientific name: Oxyops vitiosa

First released in April 1997, melaleuca weevilshave been distributed to over 150 locations.Evidence of their presence includes holes orgouges in buds and leaves. Adults are fairly easyto spot on melaleuca – they are gray-brown, withsix legs and a snout, and larger than a ladybug(up to 3/8 inch). When touched, they tend to “playdead” and fall to the ground.

Adult weevils may live longer than one year, andfemales may produce up to 1,000 eggs. Eggshatch after seven days and spend seven weeks aslarvae (immatures). Larvae grow up to 1/2 inchand are sluglike, and trail thin coils of fecal matter.Larvae are usually gray but might appear yellow attimes. When the larvae are ready to pupate, theycease feeding, crawl or drop to the ground, andspend about four weeks underground in anearthen capsule. Due to this time spent in the soil,weevils do not fare well in permanently floodedhabitats.

Agent Number 2: The Melaleuca PsyllidScientific name: Boreioglycaspis melaleucae

First releasedin April 2002,the melaleucapsyllid (SILL-id)is difficult tosee directlybecause of itssmall size (1/8inch). However,its nymphs(immatures)are easy todetect from thewaxy floccu-lence (whitefluff) that theysecrete onto melaleuca leaves and stems. Thiswax is harmless and washes off with rain. Psyllidscomplete their entire six-week life cycle on themelaleuca tree. Pale to bright yellow eggs are laidon leaves and stems and hatch in about twoweeks. Nymphs take around three weeks todevelop into adults and cause the majority of feeding damage.

The ResultsBoth the weevil and the psyllid attack only themelaleuca tree. Due to their preference for newgrowth, they are most active from late fall throughspring, when melaleuca grows most rapidly inFlorida. Psyllids may also feed on mature leaves,causing them to discolor and drop. While theyhave not been observed killing mature trees, theseagents can cause mortality in melaleuca seedlingsand saplings.

The effects of biological control agents onmelaleuca trees include defoliation, stunting ofgrowth, reduction of flower and seed production,and a brownish or generally unhealthy appear-ance. Research has demonstrated the weevil’sability to cause up to an 80% reduction in flower-ing. Over time, this damage will reduce the spreadof melaleuca stands and the costs related to con-trolling them. Biological control agents are consid-ered the best method for long-term control of suchwidespread invasive weeds, and they are a keycomponent of efforts to restore sensitive ecosys-tems such as the Everglades.

Melaleuca RemovalMelaleuca and other invasive weeds should beremoved to prevent their further spread intoFlorida’s natural areas. Contact your county’sextension office (see http://extension.ifas.ufl.edu)for guidance on removing melaleuca.

Native to Australia, this weevil feeds only on melaleuca.

The melaleuca psyllid makes its homeonly in melaleuca trees. Psyllid nymphsare shown here.

These melaleuca leaves show typical damage caused byimmature (larval) weevils.

It may look like snow, but in South Florida this white waxon melaleuca means one thing: psyllids at work.

Enemies2 2/6/04 3:49 PM Page 2