Ligustrum robustum subsp. walkeri (Sri Lankan privet)

Identity

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Preferred Scientific Name

Ligustrum robustum subsp. walkeri (Decne.) P.S. Green

Preferred Common Name

Sri Lankan privet

Other Scientific Names

Ligustrum ceylanicum Decne.
Ligustrum robustum var. walkeri (Roxb.) Bl. Var (Decne) Mansf.
Ligustrum walkeri Decne.
Phillyrea robusta Roxb.

International Common Names

French: troène de Ceylan

Local Common Names

China/Guizhou: guizhou kudingcha
India/Assam: takora; tukra
Sri Lanka: bora; borkungli; iikolee; pungalam; robust privet

EPPO code

LIGWA (Ligustrum robustum subsp. walkeri)

Summary of Invasiveness

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L. robustum subsp. walkeri is one of the most serious invasive species in the Indian Ocean islands of Mauritius and La Réunion where it is having a direct negative impact on forest biodiversity. Seeds in both islands are thought to be dispersed almost entirely by another introduced species, the red-whiskered bulbul, Pycnotus jocosus. It is already one of the dominant species in remnant Mauritian native forests and is expected to become the same in La Réunion if control efforts are unsuccessful.

Taxonomic Tree

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Domain: Eukaryota
Kingdom: Plantae
Phylum: Spermatophyta
Subphylum: Angiospermae
Class: Dicotyledonae
Order: Oleales
Family: Oleaceae
Genus: Ligustrum
Species: Ligustrum robustum subsp. walkeri

Notes on Taxonomy and Nomenclature

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The genus Ligustrum contains around 40 species and is found throughout most of the temperate and tropical Old World except Africa and the coldest regions (Green, 1987), and is a member of the Oleaceae, a medium sized family consisting of around 600 species in 25 genera. The species name relates to its rather robust nature. Recent molecular studies have revealed that Ligustrum and Syringa are closely related and exist in the subtribe Ligustrinae within the tribe Oleeae (Wallander and Albert, 2000). L. robustum contains two accepted subspecies, subsp. robustum and subsp. walkeri. The highly invasive material in the Mascarenes has been identified as belonging to subsp. walkeri, and as such this is covered alone in this datasheet.

The taxonomy and nomenclature of L. robustum subsp. walkeri is very confused. The genus Ligustrum has been the subject of repeated reviews in the past (Green, 1985; Green, 1990; Green, 1995) and the current opinion is that the distinctions between species in Ligustrum are small and some of those used to distinguish southern Indian species are not reliable. Thus, Green (1990) proposes that those species in southern India which had previously been distinguished should be considered as one variable species, Ligustrum perottettii. The taxon introduced to the Mascarenes is believed to be L. robustum subsp. walkeri. This was confirmed using molecular techniques which showed the Sri Lankan L. robustum subsp. walkeri to be identical to the Mascarene introduced material and most similar, but distinct from the southern Indian material when compared with northern Indian material (Shaw and Milne, 1999; Milne and Abbott, 2003).

Description

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L. robustum subsp. walkeri is an evergreen shrub or small tree to 10 m tall; however mature trees were observed with heights in excess of 15 m with trunks greater that 2 m in diameter in Sri Lanka, possibly due to their old age (estimated at over 100 years old). Young stems are lenticelate, glabrous or minutely puberulous. Leaves and petioles are glabrous; lamina lanceolate, glabrous, 3-9 x 5-2.5 cm, margin entire. base rounded or obtuse, attenuate into the petiole; apex acute-attenuate; venation somewhat obscure with 5-7 primary veins per side. Inflorescence terminal, pyramidal, paniculate, many-flowered, scented, 20 cm long, glabrate or minutely puberulous. Calyx campanulate, 1 mm long, more or less entire or with 4 very shallow triangular teeth. Corolla tube, white, 1 mm long, lobes 4, valvate, 2 mm long, more or less reflexed at anthesis. Stamens 2, exserted, filament inserted at top of the corolla tube, 1.5 mm long; anthers narrowly oblong, 1 mm long. Ovary rounded, 0.5 mm; style 1.5 mm long, stigma terminal, more or less fused, elongate. Fruit a berry, ellipsoid, 7-10 x 4-5 mm, bluish-purple when ripe (Dassanayake and Fosberg, 1987).

Plant Type

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Seed propagated
Shrub
Tree
Woody

Distribution

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The genus Ligustrum is found throughout most of the temperate and tropical Old World except Africa (Green, 1987), L. robustum subsp. walkeri is native to India and Sri Lanka, and is found in the hills of peninsular India where it is thought to have originated primarily in the Western Ghats, including the Palani, Nilgiri and Shevaroy Hills, and the high country of Sri Lanka; Kandy, Matale, Nuwara Eliya, Badulla, Mongerala and Ratnapura districts. In contrast, L. robustum subsp. robustum is native to central and north-eastern India, Bangladesh, South East Asia, Sumatra and southern China. L. robustum subsp. walkeri has been introduced to several Indian Ocean islands but is not recorded elsewhere.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020

Continent/Country/Region	Distribution	Origin	Invasive	Reference	Notes
Africa
Mauritius	Present	Introduced	Invasive	Lavergne et al. (1999)	First reported: before 1895
Réunion	Present	Introduced	Invasive	Lavergne et al. (1999)	First reported: 1960s
Asia
Bangladesh	Present			CABI (Undated b)
Cambodia	Present			CABI (Undated b)
China	Present			CABI (Undated a)	Present based on regional distribution.
-Fujian	Present			CABI (Undated b)
-Guangdong	Present			CABI (Undated b)
-Guangxi	Present			CABI (Undated b)
-Guizhou	Present			CABI (Undated b)
-Hubei	Present			CABI (Undated b)
-Hunan	Present			CABI (Undated b)
-Jiangxi	Present			CABI (Undated b)
-Sichuan	Present			CABI (Undated b)
-Yunnan	Present			CABI (Undated b)
India	Present			CABI (Undated b)
-Tamil Nadu	Present	Native		Chandran and Shah (1975)
Indonesia	Present			CABI (Undated a)	Present based on regional distribution.
-Sumatra	Present			CABI (Undated b)
Myanmar	Present			CABI (Undated b)
Sri Lanka	Present, Localized	Native		CABI (Undated)	Original citation: Dassanayake & Fossberg, 1987
Thailand	Present			CABI (Undated b)
Vietnam	Present			CABI (Undated b)

History of Introduction and Spread

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L. robustum subsp. walkeri was introduced to Mauritius in the late 1800s through botanical exchanges between Peradeniya Botanical Garden, Sri Lanka and Curepipe Botanical Garden, Mauritius. It was planted as a hedge in 1895 (Rouillard and Guého, 1990) and was actually propagated in native forests by P. Koenig, the Director of Forests and Gardens, in order to outcompete another invasive species Rubus alciefolius (Anon., 1903; Brouard, 1963). It was also promoted as an excellent plant for establishing in the plantations and gardens of the island (Gleadow, 1904) and for firewood (Sale, 1935). It spread rapidly in Mauritius, and by the 1930s it had already colonized all of the mountain forests (Vaughan and Wiehe, 1937) and had become the dominant species on all exposed mountain slopes and ravines excluding all other species. Now along with other invasive plants, L. robustum subsp. walkeri replaces the natural regeneration of native forest after natural senescence and death of indigenous trees. L. robustum subsp. walkeri has also been introduced to the island of Rodrigues probably as an ornamental hedge plant and has been found bearing fruit alongside rivers (Strahm, 1989), but is only recorded as naturalized, not invasive, possibly because of a lack of bird seed vectors. In Réunion, the species was probably introduced in the 1960s. It was first cultivated as a hedge in Cilaos in 1969 and had become naturalized in the forests in 1975 (Lavergne, 2000). Although it is spreading, the invasion in Réunion is still relatively young and localized, occupying only 3000 ha. It is a recognized threat to native forests and is invading progressively upwards (Lavergne, 1995).

Risk of Introduction

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Given its use as a hedge plant in the tropics it is likely that seed could be collected and distributed to other vulnerable regions by man.

Habitat

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L. robustum subsp. walkeri in its native range is to be found on the edge of forests and along roadsides, riverside embankments as well as in gardens. In forest edges it has access to light but it is capable of growing from heavily shaded forest floors; however, it can be accurately described as hemi-sciaphilous, i.e. a species that establishes in shady sites but requires light to mature. In its non-native range it is able to rapidly establish even in mature native forest following any disturbance event.

Habitat List

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Category	Sub-Category	Habitat	Presence	Status
Terrestrial
Terrestrial	Managed	Managed forests, plantations and orchards	Present, no further details	Harmful (pest or invasive)
Terrestrial	Managed	Disturbed areas	Present, no further details	Harmful (pest or invasive)
Terrestrial	Managed	Rail / roadsides	Present, no further details	Harmful (pest or invasive)
Terrestrial	Natural / Semi-natural	Natural forests	Present, no further details	Harmful (pest or invasive)
Terrestrial	Natural / Semi-natural	Riverbanks	Present, no further details	Harmful (pest or invasive)

Hosts/Species Affected

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L. robustum subsp. walkeri is not a weed of crops or pastures, its main impact being on intact native forest in the Mascarenes and as such threatens many endangered and rare species. Lavergne et al. (1999) identified 47 rare, endangered or vulnerable native Mascarene plant species which were potentially threatened by the L. robustum subsp. walkeri invasion in La Réunion.

Host Plants and Other Plants Affected

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Plant name	Family	Context	References
Cryptomeria japonica (Japanese cedar)	Taxodiaceae	Main

Growth Stages

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Post-harvest, Seedling stage

Biology and Ecology

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Genetics

The chromosome number is n=23 (2n=46), the same for all members of the tribe Oleeae.

Physiology and Phenology

The plant germinates from seed from within the fruit, which is either dropped from the parent tree or after passage through the gut of a bird. Flowering and fruiting occurs twice per year in Sri Lanka but only once in La Réunion where it reaches a peak in September. Seeds are able to survive for months in the soil awaiting favourable germination conditions. Explosive germination and establishment of seedlings follows, especially after disturbance events with an observed average of 189 seedlings/m² in the field (Lavergne, 2000). Seedlings grow faster than most of their competitors in the forest, with an average height increment of 9 cm per year. Trees are often many branched, and resprout vigorously if felled or cut.

Reproductive Biology

L. robustum subsp. walkeri can reach the age of first reproduction at 5-7 years in a forest margin with partial sun exposure. Trees can be self-pollinated in the field with bagged panicles producing a mean of 11.5 fruits containing viable seeds (Lavergne et al., 1999). It is self compatible which is rare in the Oleaceae family (Bradley and Griggs, 1963) and enables a new population to establish around one founder individual. The density of the viable seed bank is estimated to be around 60/m² in La Réunion (Lavergne, 2000). The volume of fruit set is correlated with the amount of light available and can reach a mean of 9000 fruits per mature shoot over 9 months in full light in La Réunion. The nature of the flower panicle is such that generalist insects attracted by the strongly-scented flowers can pollinate it easily. There is little difference in fruit production between plants in the native range as compared to the introduced range. The fleshy fruits are adapted to both short and long-distance transport that results in new foci of infestation by means of bird dispersion. Trees may live for over 100 years.

Environmental Requirements

L. robustum subsp. walkeri is to be found in its native range in wet and intermediate low montane regions often along streams at 450-2000 m altitude (Cronk and Fuller, 1995), from 725-1375 m although rarely below 1000 m in Sri Lanka, and from near sea level in Mauritius to 1700 m on the slopes of Piton de Neige (Lavergne et al. 1999). It prefers sites with high temperature and rainfall such as sholas, dense humid forests with a closed canopy 18-25 m high. The understorey is typically dense with high numbers of epiphytes. It can be found on sandy, well-drained soil in Sri Lanka as well as heavier clay soils whilst it thrives on volcanic soil characterisitics on La Réunion. Invasion often follows a disturbance event be it natural such as a cyclone or man-made. i.e. forest clearances or road building.

Associations

L. robustum subsp. walkeri is a host for the tea shoot hole borer Euwallacea fornicatus (Eichhoff) in its native range in Sri Lanka.

Latitude/Altitude Ranges

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Latitude North (°N)	Latitude South (°S)	Altitude Lower (m)	Altitude Upper (m)
		0	2000

Air Temperature

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Parameter	Lower limit	Upper limit
Absolute minimum temperature (ºC)	3
Mean annual temperature (ºC)	16	24
Mean maximum temperature of hottest month (ºC)	19	26
Mean minimum temperature of coldest month (ºC)	14	23

Rainfall

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Parameter	Lower limit	Upper limit	Description
Mean annual rainfall	1734	2650	mm; lower/upper limits

Rainfall Regime

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Bimodal
Uniform

Soil Tolerances

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Soil drainage

free

Soil texture

heavy
light
medium

Natural enemies

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Natural enemy	Type	Life stages
Epiplema albida	Herbivore	Leaves
Palpita celsalis	Herbivore	Leaves
Rhopobota naevana	Herbivore	Leaves
Thedgonia ligustrina	Pathogen	Leaves

Notes on Natural Enemies

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The hemibiotrophic plant pathogenic fungi Thedgonia ligustrina (Dothideales) is found on L. robustum subsp. walkeri in its native range but it is far from common. The same pathogen is also found infecting Ligustrum ovalifolium in Europe and isolates from Europe are capable of infecting L. robustum subsp. walkeri seedlings from seed collected in La Réunion in laboratory conditions (Shaw et al., 2001). This pathogen arrived accidentally in La Réunion in 2003, probably on imported hedge privet from Europe, and was observed causing severe defoliation in the field in Cilaos, La Réunion (C. Lavergne, pers. comm.). Both Rhopobota naevana and Palpita celsalis were found to be serious pests of Ligustrum robustum subsp. walkeri in Sri Lanka, injuring young growing leaves and stunting growth; however, these species were found to be generalist and not appropriate for biological control.

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

Frequent tropical storms in its introduced range facilitates the transport of seed by water, allowing the colonization of gulleys and other sites below existing infestations.

Vector Transmission (Biotic)

The history of the L. robustum subsp. walkeri invasion in Indian Ocean islands has been followed almost identically by the introduced red-whiskered bulbul, Pycnotus jocosus, a bird that feeds and spreads the berries (Cheke, 1987; Barre et al., 1996). This alien species is the main vector for spread in the Mascarenes.

Intentional Introduction

People are still using L. robustum subsp. walkeri as an ornamental species and it is commonly found as a hedge plant in La Réunion, even in Cilaos where its invasion of the native forest is well publicized. Seeds and seedlings are collected from the forest to plant in gardens.

Plant Trade

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Plant parts liable to carry the pest in trade/transport	Pest stages	Borne internally	Borne externally	Visibility of pest or symptoms
Growing medium accompanying plants	fruits; seeds

Impact Summary

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Category	Impact
Animal/plant collections	None
Animal/plant products	None
Biodiversity (generally)	Negative
Crop production	None
Environment (generally)	Negative
Fisheries / aquaculture	None
Forestry production	None
Human health	None
Livestock production	None
Native fauna	Negative
Native flora	Negative
Rare/protected species	None
Tourism	Negative
Trade/international relations	None
Transport/travel	None

Impact

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Reduced biodiversity and homogenization of the attractive natural environment could lead to a reduction in eco-tourism potential which is a major driving force for the local economy. Cutting and stump treatment of 1 ha of L. robustum subsp. walkeri invasion was estimated at 3243FF (approximately UK£330 or US$500 per ha) for the year 1998-99 (Lecouer, 1997). In 1990-91, 400 ha were treated (Lavergne, 2000), with an estimated cost of almost 1.3 million FF (approximately UK£130,000 or US$200,000) per year for only a limited control effort.

Environmental Impact

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The major impact of L. robustum subsp. walkeri is on the light regime in invaded areas which must have significant effects on ecosystem function, although this has not been quantified.

Impact: Biodiversity

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Although it is difficult to distinguish the impact of an invasive species from human disturbance, the effect of the L. robustum subsp. walkeri invasion in the Mascarenes could be devastating. It is already reducing the number of native species found in forests and threatening a number of rare endemic species in La Réunion. There is a possibility that pollinators are drawn away from native species in favour of the attractive flower panicles of L. robustum thereby reducing their reproductive capability.

Social Impact

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Reduced eco-tourism as a result of reduced biodiversity will have social impacts as yet undetermined.

Risk and Impact Factors

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Invasiveness

Proved invasive outside its native range
Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
Highly mobile locally
Has high reproductive potential

Impact outcomes

Damaged ecosystem services
Ecosystem change/ habitat alteration
Negatively impacts agriculture
Negatively impacts animal health
Reduced native biodiversity

Impact mechanisms

Competition - monopolizing resources
Pest and disease transmission

Likelihood of entry/control

Highly likely to be transported internationally deliberately
Difficult/costly to control

Uses

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Without doubt the main application to which L. robustrum is put to use is as a garden plant since it is generally free of pests and tolerant of the pollution in cities, and is therefore one of the most widely planted of all flowering shrubs. For example, L. lucidum is a common street tree in Mexico City where pollution is a serious factor (Chacalo, 1994). L. robustum wood is hard and used in its native range in house construction, to make tool handles, brooms for separating chaff from wheat, and as a fuelwood and charcoal. The seeds of the related species L .japonicum, L. indicum, and L. ibota can be roasted and used as a coffee substitute (Hora, 1981). Honey bees (Apis mellifera) accounted for up to 99% of all insect visits to L. obtusifolium over a six day period in Korea (Kim and Choi, 1987). Indeed, in part of its native range, L. robustrum subsp. walkeri is quoted as being a major source of pollen and nectar in the Kodai Hills in Tamilnadu, India (Chandran and Shah, 1975).

There is increasing evidence that many Chinese medicinal herbs are promising biological response modifiers in cancer treatment. The extracts of some Chinese herbs have shown the ability to stimulate the bone marrow and improving the peripheral white cell counts in rats. Included in this group is L. lucidum, which may exert anti-tumour effects via augmentation of phagocyte and lymphokine-activated killer cell activities (Lau et al., 1994). Furthermore, extracts from the leaves of L. japonicum have been shown to exhibit inhibitory activity against implanted tumours in mice (Hashi, 1991). The fruits of L. vulgare are also used as a tonic to treat hypertension in Azerbaijan (Willems, 1988).

In China, the leaves of L. robustum are harvested and dried to make an infusion which has the common name of kudingcha, referring to any tea made from a suite of native plant species but L. robustum provides a high flavonoid content (Yu, 1997). In China's southern provinces, mature trees were observed in gardens from which the leaves are harvested to make this tea. China wax is harvested from the coccid Ericerus pela and refined for commercial uses, produced mainly in Sichuan, Yunnan, Guizhou, Hunan and Shanxi, China. The most suitable food-plants for the coccid are L. lucidum and Fraxinus chinensis, both Oleaceae (Li, 1985). The insects and their secretions are harvested and boiled with water to extract the raw wax, while the insect bodies, which settle to the bottom are used as food for swine.

Similarities to Other Species/Conditions

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The taxonomy and identification of L. robustum subsp. walkeri is complex and difficult and under revision, and it can be confused with many Ligustrum species present in the Indian subcontinent, especially when immature and when not in flower or bearing fruit. Examples include L. walkeri, L. roxburghii, L. neilgherrense, L. perottetii and L. confusum. It bears superficial similarity to some species of Ficus but does not produce a sticky sap when wounded. L. robustum subsp. walkeri can be distinguished from the closest relatives namely: L. perottettii, L. confusum and L. compactum (Green, 1990) by a combination of leaf, inflorescence (generally larger and more open panicle) and its smaller more pedicellate flowers, pedicel, calyx and corolla lengths.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control

One of the techniques being tested for controlling L. robustum subsp. walkeri is the encouragement of indigenous species such as Dombeya sp., Monimia sp. and Weinmannia tinctoria as understorey components through silvicultural tending and release (Figier and Souleres, 1991).

Mechanical Control

Mechanical control is difficult since the plant can regenerate vigorously after treatment. In La Réunion a 100 m² plot under native scrub forest which was cut had around 15,000 individuals per ha after two years and 100% of cut individuals had coppiced (Macdonald et al., 1991). Young plants may be hand pulled but older shrubs need to be dug out.

Chemical Control

In invaded and delicate ecosystems, spraying with non-specific chemicals is not an option and accessing L. robustum subsp. walkeri plants on steep slopes is extremely difficult. For the closely related L. sinense, foliar applications of glyphosate are effective, and was susceptible to cut-stump applications of triclopyr or glyphosate. Stems <1.25 cm in diameter are susceptible to basal bark application of triclopyr ester in oil whereas larger stems must be notched or frilled and metsulfuron has been reported as highly effective when applied to the foliage of actively growing plants. Direct stem injection is a potentially useful approach to controlling invasive woody species if access is possible.

Biological Control

There is little predation by browsing animals due to the high levels of ligustrin, a poisonous glycoside, in the foliage (Burrows and Tyrl, 1983). A biological control research programme has identified a suitably specific moth, Epiplema albida, which will be considered as a potential classical biological control agent. The accidental arrival of the plant pathogen Thedgonia ligustrina holds good promise as it is already implicated in heavy defoliation in the field in Cilaos, La Réunion (C. Lavergne, pers. comm.). Numerous insects and fungal pathogens were rejected during the recent classical biological control programme carried out by CABI Bioscience, Egham, UK.

Integrated Control

The most common approach to controlling privet is to cut the tree down and apply a stump treatment chemical to the cut surface. However, as L. robustum subsp. walkeri resprouts vigorously, it is likely to require follow up spray treatments to control subsequent growth.

References

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Anon., 1903. Forest Plantations Annual Report, Mauritius: Woods and Forests Department.

Barré N; Barau A; Jouanin C, 1996. Oiseaux de La Réunion. Paris, France: Les Editions du Pacifique.

Bradley MV; Griggs WH, 1963. Morphological evidence of incompatibility in Olea europaea L. Phytomorphology, 13:141-156.

Brouard NR, 1963. A history of Woods and Forests in Mauritius. Port Louis, Mauritius: Government Printer.

Burrows GE; Tyrl RJ, 1983. Ornamental plants potentially hazardous to cattle. Bovine Practitioner, 18:188-194; [11 colour fig.]; 7 ref.

Chacalo A; Aldama A; Grabinsky J, 1994. Street tree inventory in Mexico City. Journal of Arboriculture, 20, 222-226.

Chandran KS; Shah FA, 1975. Beekeeping in Kodai Hillsa (Tamilnadu, India). Indian Bee Journal, 36:1-9.

Cheke AS, 1987. An ecological history of the Mascarene Islands, with particular reference to extinctions and introductions of vertebrates. In: Diamond AW, ed. Studies of Mascarene Island Birds. Cambridge, UK: Cambridge University Press, 5-89.

Cronk CB; Fuller JL, 1995. Plant Invaders the threat to natural ecosystems. London, UK: Chapman and Hall.

Dassanayake MD; Fosberg FR, 1987. A revised handbook to the flora of Ceylon. New Delhi, India: Amerind Publishing.

Figier J; Souleres O, 1991. The problem of invasion by exotics. Bois et Forets des Tropiques, No. 229:31-34

Gleadow RM, 1904. Report on the forests of Mauritius with a preliminary working plan. Mauritius: Woods and Forests.

Green PS, 1985. Ligustrum robustum subsp. walkeri (Oleaceae). Kew Bulletin, 40:130.

Green PS, 1987. The Oleaceae. In: Dassanayake MDF, ed. Flora of Ceylon, Vol VI. New Delhi, India: Amerind Publishing.

Green PS, 1990. Ligustrum (Oleaceae) in Southern India. Kew Bulletin, 45:693-696.

Green PS, 1995. Taxonomic notes relating to Ligustrum (Oleaceae). Kew Bulletin, 50:379-386.

Hashi M, 1991. Antitumour effects and anti-complementary effects of tree polysaccharides. Bulletin of the Forestry and Forest Products Research Institute, Ibaraki, 121-148.

Hora B, 1981. The Oxford Encyclopedia of Trees of the World. New York, USA: Oxford University Press.

Kim YSC; Choi SY, 1987. Studies on the foraging activity of honeybees (Apis mellifera) on Ligustrum obtusifolium. Korean Journal of Apiculture, 2:101-107.

Lau HHS; Ruckle HC; Botolazzo T; Lui PD, 1994. Chinese medicinal herbs inhibit growth of murine renal cell carcinoma. Cancer Biotherapy, 9:153-161.

Lavergne C, 1995. Contribution a l'étude du troène envahissant à La Réunion. La Réunion, France: Office National Des Forêts & Conseil Régional de la Réunion.

Lavergne C, 2000. Étude de la stratégie du Troène de Ceylan, Ligustrum robustum subsp. walkeri. + La réunion et des caractéristiques du milieu envahi. PhD Thesis. ENGREF, Université de La Réunion.

Lavergne C; Rameau JC; Figier J, 1999. The invasive woody weed Ligustrum robustum subsp. walkeri threatens native forests on La Réunion. Biological Invasions, 1:377-392.

Lecouer N, 1997. Aménagement de la réserve biologique domaniale du Matarum (Cilaos) 1998-2007. Saint Denis, La Réunion, France: Office National des Forêts.

Li CK, 1985. China wax and the China wax scale insect. World Animal Review, No. 55:26-33

Macdonald IAW; Thébaud C; Strahm W; Strasberg D, 1991. Effects of alien plant invasions on native vegetation remnants on La Réunion (Mascarene Islands, Indian Ocean). Environmental Conservation, 18:51-61.

Milne RI; Abbott RJ, 2003. Geographic origin and taxonomic status of the invasive Privet, Ligustrum robustum (Oleaceae), in the Mascarene Islands, determined by chloroplast DNA and RAPDs. Heredity, 92:78-87.

Rouillard G; Guého J, 1990. Le Jardin Botanique de Curepipe. Curepipe, Mauritius.

Sale GN, 1935. Exotics in Mauritius. British Empire Forestry Conference, South Africa, 3-12.

Shaw RH; Djeddour D; Gassmann A, 2001. The Biological Control of Ligustrum robustum subsp. walkeri on the island of La Réunion. Final report, Nov 1997- November 2001. Egham, UK: CABI Bioscience.

Shaw RH; Milne R, 1999. The use of molecular techniques in the classical biological control programme against an in vasive ligustrum species in La Réunion. In: the Xth International Symposium on Biological Control of Weeds, 4-14 July 1999. Bozeman, USA: Montana State University.

Strahm W, 1989. Plant Red Data Book for Rodrigues. Konigstein, Germany: Koeltz Scientific Books.

USDA-ARS, 2003. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

Vaughan RE; Wiehe PO, 1937. Studies on the vegetation of the Mauritius. 1. A preliminary survey of the plant communities. Journal of Ecology, 25:289-342.

Wallander E; Albert VA, 2000. Phylogeny and Classification of Oleaceae Based on RPS16 and TRNL-F sequence data. American Journal of Botany, 87(12):1827-1841.

Willems M, 1988. Quantitative determination of secoiridoid glucosides from the fruits of Ligustrum vulgare by means of HPLC. Planta Medica, 54:66-68.

Yu JP, 1997. The plant resources and its chemical constituents of Kuding Tea in Guizhou Province. Journal of Plant Resources and Environment, 6(2):22-25.

Distribution References

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

CABI, Undated b. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Chandran KS, Shah FA, 1975. Beekeeping in Kodai Hillsa (Tamilnadu, India). In: Indian Bee Journal, 36 1-9.

Lavergne C, Rameau J C, Figier J, 1999. The invasive woody weed Ligustrum robustum subsp. walkeri threatens native forests on La Réunion. Biological Invasions. 1 (4), 377-392. http://www.springerlink.com/(2dmv3a55y2ikkn55bfmksi45)/app/home/contribution.asp?referrer=parent&backto=issue,6,10;journal,24,26;linkingpublicationresults,1:103794,1 DOI:10.1023/A:1010001529227

Links to Websites

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Website	URL	Comment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gateway	https://doi.org/10.5061/dryad.m93f6	Data source for updated system data added to species habitat list.

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Datasheet

Ligustrum robustum subsp. walkeri (Sri Lankan privet)

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