Melaleuca Madness

This discussion topic submitted by Joseph Shacat (shacatja@po.miamioh.edu) on 7/13/98.

The melaleuca tree: what is this thing, anyway?

In the early 1900Õs, the tree Melaleuca quinquinervia was imported to South Florida from Australia in efforts to beautify and "dry up" the Everglades. With no natural predators in the Everglades, this harty
tree has literally taken over some parts of the everglades. Since its introduction to South Florida, its population has exploded to a point where Melaleuca management has become a primary concern for many
Floridians. Due to several reproduction and survival adaptations of the plant, however, controlling it has been nearly impossible. In the past, control has been limited to physical methods (removal of the trees) and herbicidal methods. Recently, however, biological control was introduced in the form of an Australian beetle that feeds on the plant.

I. Family background
A. Australian family Myrtaceae
1. Over 3000 species in the family
a. Many cultivatedfor human use
b. Also in the family are Eucalyptus (gum) and
Callistemon (bottlebrush)
2. 80 genera in the family
3. 2 major subfamilies
a. Leptospermoideae with capsular fruits
b. Myrtoideae with fleshy fruits
4. Genus Melaleuca has over 200 species
a. M. quinquinervia is the only one found
in S. Florida
B. Physical characteristics of Myrtaceae family
1. Most have numerous stamens on a cup-shaped receptacle with
the ovary below
2. Leaves are simple and entire
3. Plants are usually aromatic

II. Physical characteristics of M. Quinquinervia
A. Common names include cajeput, punk, and broadleaf paperbark tree
B. Spongy, flaking bark
1. Bark is white to cream-colored
C. Longitudinally parallel-veined leaves
1. Grey-green in color
2. Elliptic to lance-shaped
3. 2 - 4.75 inches long
D. Can grow up to 50 feet high
E. Flowers occur at the ends of stems
1. Each flower has:
a. 1 stigma
b. 30 - 40 white stamens
c. 5 white petals
d. 5 sepals
2. Flower spikes can be 1 - 4 inches long
3. Flowers yearround, but heaviest in summer and fall
4. Pollinated by insects
5. Remaning fruit is a woody capsule (.1 - .2 inches long)
a. 200 - 300 seeds per capsule
b. capsules can stay attached for up to 10 years
c. single tree can hold up to 20 million seeds

III. Reproduction
A. Seeds released under stress
1. Includes freezing, draught, fire, herbicide treatment,
breaking the plant
B. Dispersal usually one to one and a half tree lengths
1. 200m once every several years
2. 2 km once in 20 years
C. Moist soil required for germination
D. Seeds are sensitive to drying but can withstand wet conditions
E. Prolific sprouting can occur at the base of a cut or burned tree

IV. Introduction to S. Florida
1906: John C. Gifford, U. of Miami Forestry Professor Planted at home in Biscayne Bay and a nursery in Davie, Broward County

1912: A.H. Andrews released seeds in Estero, Lee County

1936: H. Stirling released seeds by airplane over the Everglades

1940's: Hundreds of thousands of seedlings planted on rim canal of Lake Okeechobee

1950's: Melaleuca in widespread use by landscaping & nursery industry

V. Potential range in S. Florida
A. Grows along roadsides, on ditch banks, along rights-of-way, in lake margins, pastures, pine flatwoods, mesic praries, sawgrass marshes, and cypress stands
1. Also in mangroves (M. Quinquinervia has some
salt tolerance)
2. Displaces cypress in ecotone between pine and cypress
3. Altered hydrologic patterns due to water management opens
up all of S. Florida to exotic species invasion
B. Potential range of the tree includes the entire area south of
Lake Okeechobee
C. Could inhabit the entire Gulf Coast if left uncontrolled

VI. Melaleuca mapping and counting
1977: LANDSAT data was put through digital analysis Results were
unreliable and inconclusive

1981: U.S. Forestry Service found Melaleuca in over 7.6 million acres 40,300 acres of "pure melaleuca" Same test in 1987 yielded 47,000 acres

1984: Feasibility study of photographic remote sensing Would analyze color infrared photography

1992: S. Florida Water Management District analyzed false color infrared photography Found 26,000 acres of mature, monotypic stands over 2.5 acres in size Current Estimates:
1. 388,896 acres of Melaleuca
2. Occurs on 7.7 million acres
3. 47,000 monoculture areas

VII. Controling Melaleuca
A. Potential consequences of uncontrolled Melaleuca
1. 50% reduction in tourism
2. Drive down the prices of pine and cypress mulches
3. Increased difficulties for those allergic to Melaleuca
pollen
4. Beekeeping industry could lose $12.3 million
5. Water management concern due to increased
evapotranspiration of tree as opposed to sawgrass
6. Increased fire risk because Melaleuca burns much hotter
than sawgrass
B. Mechanical control efforts
1. Effective only along canal and utility rights of way
2. Stumps require herbicide treatment
3. Felled trees must be removed immediately to prevent seed
dispersal
4. Wood is used for mulch
a. Wood chips sit for 100 days in piles that can reach
150 degrees to kill seeds
C. Herbicidal control efforts
1. "Girdle" technique using ARSENAL
a. A notch is chopped around the tree
b. ARSENAL is injected into the fresh cut wood
2. Soil application used occasionally, but kills surrounding
vegetation as well
3. Foliar-active herbicides used only in large stands
a. applied from overhead by a plane
b. 700 acres treated by arial herbicide
application in 1997
D. Biological control methods
1. Melaleuca weevil
a. Species Oxyops vitiosa - Melaleuca snout beetle
imported from Australia
b. Feeds on the young leaves and flowers of plants
c. Can kill a seedling up to 10 feet tall
d. Larvae require dry soil to grow, which makes it
ineffective in the Everglades
e. About 8,000 weevils have been dispersed in
S. Florida since April 1997
2. Melaleuca sawfly
a. Feeds on older melaleuca leaves
b. Larvae burrow into the tree bark, allowing for use
in the Everglades
c. Still being researched for possible negative
effects on the habitat

VIII. Melaleuca legislation
A. Designated a Federal Noxious Weed
B. FloridaProhibited Plant
1. This Primarily prohibits commercial trade
C. Many S. Florida communities require removal during real estate
development
D. Proposal HB823 would authorize the private harvesting of
melaleuca on state and federal lands

Bibliography

1. "Bill Steps Up Melaleuca Eradication, Works in Floridians'
Best Interest." Sun Sentinel. Page 8A: February 6, 1996.

2. Bodle, Michael J., Amy P. Ferriter, and Daniel D. Thayer.
"The Biology, Distribution, and Ecological Consequences of
Melaleuca quinquinervia in the Everglades."
Pub. in Everglades: The Ecosystem and its Restoration.
Ed. by Steven M. Davis and John C. Ogden.
St. Lucie Press, Delray Beach, FL: 1994.

3. Conde, Louis F. and Rockwood and Richard F. Fisher.
"Growth Studies on Melaleuca." Pub. in
Proceedings of Melaleuca Symposium. Compiled by R. K. Geiger.
Florida Div. of Forestry: June 1981.

4. Melaleuca Management Plan for South Florida.
Melaleuca Task Force: April, 1990.

5. Santaniello, Niel. "New Leaf-eating Beetle Ready to Bug
Melaleuca." Sun Sentinel. Page 4B, January 10, 1997.

6. Santaniello, Niel. "Munchin' Beetle Will Work For Food:
Melaleuca." Sun Sentinel. Page 1B, June 7, 1998.

7. 97 Everglades Annual Report. South Florida Water Management
District. p. 24. 2159 FCD 1.E 82/1997.


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