Authors: Michael S. Batcher, eds. Mandy Tu and John M. Randall, Global Invasive Species Team, The Nature Conservancy
- Melia azedarach is a deciduous tree growing to 50 ft. (15.2 m) in height and 2 ft. (0.6 m) in diameter.
- The leaves are alternate, bi-pinnately compound, 1-2 ft. (0.3-0.6 m) in length and turn golden-yellow in fall.
- Flowering occurs in the spring, when showy, lavender, 5-petaled flowers develop in panicles.
- Fruit are hard, yellow, marble-sized, stalked berries that can be dangerous on sidewalks and other walkways. Seeds are spread by birds.
- Ecological Threat
- Melia azedarach invades disturbed areas and is commonly found along roads and forest edges. It has the potential to grow in dense thickets, restricting the growth of native vegetation. Melia azedarach is native to Southeast Asia and northern Australia. It was introduced into the United States in the mid 1800s for ornamental purposes.
DESCRIPTION AND DIAGNOSTIC CHARACTERISTICS
Melia azedarach is a small to medium-sized shrub or tree in the mahogany family (Meliaceae). Branches of chinaberry are stout, with purplish qk and dotted with buff-colored lenticels. Leaves are twice to three-times compound, alternate, and puberulent to glabrous. Leaflets are 2-8 cm long, serrate or crenate, dark green above, often with sparse hairs along the veins and lighter green and generally smooth below. The inflorescence is a panicle from leaf axils and from leafless nodes on the lower part of the new growth. The perfect flowers are 5-parted. Sepals are green, 1.5-2 mm long. Petals are pinkish lavender, ligulate, 1-1.3 cm long. Stamens are united into a cylindrical, dark purple tube, 6-8 mm long, cut at the apex into 15-25 slender teeth. Each flower has ten anthers. Flowers are fragrant. The fruit is a stalked, one-seeded drupe that is greenish yellow to yellowish tan, globose, and 1-1.5 cm in diameter.
M. azedarach is distinguished from other members of the Meliaceae in the southeastern U.S. by the nature of its compound leaves, and by its drooping, persistent clusters of yellowish fruits. M. azedarach is not easily confused with any other plants in its introduced North American range (K. Burks, personal communication).
M. azedarach is an invader of disturbed habitats, and is highly resistant to insects and other pathogens . M. azedarach has a high fruit and seed output, and the fruits are consumed by birds which then disperse the seeds. M. azedarach leaf litter has been evaluated as a potential soil amendment that can increase mineralizable nitrogen and increase soil pH in acidic soils. Extracts of the plant have been used for various medical purposes, including the treatment of viral infections such as herpes.
The most effective means of control are cut-stump and basal bark applications of triclopyr-based herbicides. Dilute foliar treatments with triclopyr-based herbicides provide less effective control and require large volumes of herbicide solution.
M. azedarach is native to Southeast Asia and northern Australia. In the New World, it is commonly cultivated as a shade or reforestation tree, and has escaped to the wild throughout tropical America, from the southeastern U.S. and Mexico to Argentina, and to some Caribbean islands (including Puerto Rico). In North America, M. azedarach is established from Virginia, south through Florida, and west to eastern Texas. Reported occurrences of M. azedarach in North America include: Alabama, Arizona, Arkansas, California, Delaware, Florida, Georgia, Hawaii, Louisiana, Maine, Mississippi, Missouri, New Mexico, New York, North Carolina, Oklahoma, Sonora, South Carolina, Tennessee, Texas, Utah, and Virginia.
IMPACTS AND THREATS POSED BY Melia azedarach
M. azedarach can invade disturbed and relatively undisturbed areas, and by doing so, it can decrease native biodiversity. M. azedarach has numerous defenses against insects and other plant pathogens, giving it a competitive advantage over many native species. Its leaf litter can increase the pH of soils and add nitrogen, significantly altering soil chemistry. M. azedarach is a prolific seed producer, and birds readily disperse its seeds. This invasive plant can also successfully reproduce vegetatively, forming dense thickets. These characteristics contribute to its becoming established throughout much of the southeastern United States, and negatively impacting native populations of plants and animals. M. azedarach occurs primarily in disturbed areas, but it has begun to invade relatively undisturbed floodplain hammocks, marshes, and upland woods in Florida. In Texas, riparian woodlands and upland grasslands have also been extensively invaded by M. azedarach.
M. azedarach invades along road rights of way, fencerows, and other disturbed areas. It has also been found in upland grasslands, woodlands, and riparian areas in the southeastern U.S. and in southwestern Africa.
BIOLOGY AND ECOLOGY
Little has been written on the ecology of M. azedarach. Based on general descriptions of habitat, it is likely that M. azedarach requires open sun, is not shade tolerant, and is adapted to a wide range of soil moisture conditions. In South Africa, M. azedarach has spread along streambanks and can often be found along roadsides.
Horticultural references indicate that M. azedarach is fast growing. It can reach 6-8 meters in height within four or five years. Maximum height can be 12-16 meters. M. azedarach is highly tolerant of heat, drought, and poor soil conditions, and can quickly provide dense shade.
In comparative studies of plant growth in India, M. azedarach completed most growth during the initial dry part of the growing season, indicating that it uses reserves from the preceding year for growth. M. azedarach also has a shallow root system, generally within the top 70 cm of the soil, and allocates most of its photosynthate into aboveground shoots.
The leaf litter of M. azedarach can significantly increase the ash alkalinity (an estimate of organic anion content) of the soil, which results in an overall increase in pH of the soil. Leaf litter of M. azedarach was also effective in reducing aluminum levels in soil. Decaying M. azedarach leaf litter can enhance the soil concentration of mineralizable nitrogen by an amount comparable to nitrogen-fixing legumes.
M. azedarach flowers and fruits when it reaches the size of a shrub. In North America, flowers are produced in the spring. Fruits are long-maturing, large in number, and persist past leaf fall. The fruits are poisonous to humans and to some other mammals. Birds, however, eat and disperse the fruits and seeds, but may sometimes gorge themselves to intoxication.
Seeds of M. azedarach are highly tolerant of desiccation, surviving to 3.5% moisture content. The seeds can remain viable for prolonged periods, up to at least 26 months.
M. azedarach also reproduces vegetatively by forming root suckers. This ability can often result in dense monotypic thickets.
M. azedarach is often planted as an ornamental shade tree. Several compounds from Chinaberry have been isolated for medical purposes. Meliacine, a peptide isolated from leaves of M. azedarach, exhibits potent activity against herpes simplex type 1 (HSV-1). M. azedarach has also been used as an abortifacient, an antiseptic, a purgative, a diuretic, an insect repellent, etc..
Potential for Restoration of Invaded Sites
M. azedarach has a high degree of reproductive vigor, a wide range of adaptability to different soil conditions, has numerous defenses against pests and predators, and produces copious amounts of bird-dispersed seeds. If controlled during the early stages of establishment, the potential for successful management is high. The potential for large-scale restoration of wildlands where M. azedarach has already become established, however, is probably low.
The best control of M. azedarach, as reported by land stewards/managers, occurs with the use of chemical methods. Manual/mechanical methods as well as the potential for biological control of M. azedarach, is limited. No studies were found which determined if prescribed fire would help in the control of this species.
M. azedarach has the ability to send root and stem suckers from underground storage organs. Mechanical methods of control may therefore be ineffective in controlling the spread and extent of chinaberry.
The control method of choice is a basal bark application of triclopyr (brand names Garlon®, Pathfinder II®, and others). A 10% solution of Garlon® 4 works when applied as a 20 cm (8-inch) band near the base of the trunk. According to Greg Jubinsky from the Florida Bureau of Aquatic Plant Management, a 10 cm (4-inch) band of Pathfinder II® (a pre-mixed 18% solution of triclopyr) at the base of the trunk is also effective. Jubinsky reports that a cut stump treatment of 8% Garlon® 4 or Pathfinder II® is also nearly 100% effective. A foliar treatment using a 1% solution of Garlon® 3A provides good control, but high volumes of the solution must be applied.
No biocontrols for M. azedarach have been identified.
Control efforts must be repeated and monitored for three to five years following the initial treatment, to ensure the control of chinaberry. In natural areas management, monitoring programs will likely combine changes in abundance of M. azedarach with changes in abundance of desirable native species or changes in community attributes that are the targets of management. Such programs should have explicit objectives that can be measured and that are meaningful from both a biological and management standpoint. These objectives may vary depending on the abundance of M. azedarach and other invasives. For instance, the objective of managing a forest with 40% cover of M. azedarach may be to reduce M. azedarach cover to 20%. On the other hand, an appropriate management goal for a site with 10% cover of M. azedarach may be to prevent an increase of more than 10% total cover (20% total). In addition, increasing regeneration of native species may be an important objective. Monitoring the status of other conservation targets, such as invertebrates dependent on specific nectar sources, may be more important than tracking invasive plant species abundance. In general, the objectives of monitoring should track those of management.
In terms of effort (number of plots established and monitored), transects or long, linear plots are more effective in providing sufficient statistical power to determine change than square or broadly rectangular quadrats. Analyses of plant species composition and abundance can be simplified by (1) collecting data on abundance of dominant species; (2) collecting data on all species and pooling data on less abundant species; and (3) pooling data on species by placing them in guilds (invasive grasses, invasive legumes, native grasses, etc.).
While generally a research technique, measuring change, or lack thereof, in control (unmanaged) areas can be an effective way of assuring that changes detected in treated areas are actually the result of the treatment and not of other factors such as limited rainfall or a wildfire. In forest communities that are in early successional stages or recently disturbed, declines in abundance of the M. azedarach may occur over time without management.
M. azedarach has a distinct signature on color-infrared aerial photography, which may make this an appropriate tool for monitoring the spread of M. azedarach stands.
The following research topics need attention: 1) What are the mechanisms of M. azedarach invasion and spread in a variety of fragmented forest landscapes? 2) What is the light environment of disturbed forests and the corresponding tolerance limits for M. azedarach reproduction and survival? 3) What are the effects of M. azedarach thickets on herb layer species? 4) To what extent are deer a factor in fostering invasion by M. azedarach? 4) Which if any insects or pathogens are effective at limiting M. azedarach abundance in its native range? 5) What roles do logging and other forestry practices play in the successful spread of M. azedarach? 6) How could forestry operations be carried out to prevent invasion by M. azedarach? 7) Which species replace M. azedarach when control succeeds? 8) Do prescribed burns reduce or eliminate M. azedarach and encourage regeneration of native species in forest types that are fire-influenced?
Work is needed on more efficient control methods, especially where cutting is used. Standard tools such as weed whackers, brush hogs and other equipment are not designed for cutting this species or for use inthe kinds of habitat it invades.
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- ↑ Valladares, G., M.T. Defago, S. Palacios, and M.C. Carpinella. 1997. Laboratory evaluation of Melia azedarach (Meliaceae) extracts against the elm leaf beetle (Coleoptera: Chrysomelidae). Journal of Economic Entomology. 90(3): 747-750. 3.0 3.1
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- ↑ Noble, A.D., I. Zenneck, and P.J. Randall. 1996. Leaf litter ash alkalinity and neutralization of soil acidity. Plant and Soil. 179(2):293-302. 6.0 6.1 6.2
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