2 Plant Protection Quarterly Vol.17(1) 2002

NameBotanical nameThe generic name Ziziphus is derived from‘zizouf’ (Pareek 1983) or ‘ziziphon’ (Par-sons and Cuthbertson 1992), the Arabicand Greek names respectively of the treeZ. lotus or the fruit thereof. An alternative,though not original, spelling of the genericname is Zizyphus. The specific name‘mauritiana’ derives from the island ofMauritius where the species was perhapsfirst formally collected.

Common nameIn Australia, Ziziphus mauritiana Lam. iscommonly referred to as chinee apple(Anderson 1993), presumably after its ap-parent association with early Chinese set-tlers. Internationally, it is probably betterknown as Indian jujube or by itsBaluchistani (Indian) name ber (Pareek1983). Under a taxonomic arrangementthat equates Z. mauritiana to Z. jujuba Lam.non Mill., the common names Chinese ju-jube, Chinese ber or Chinese date couldalso be applied (Walker et al. 1990, Parsonsand Cuthbertson 1992). The wide geo-graphic area over which the plant eitheroccurs naturally, is under cultivation orhas naturalized, means that many lan-guages other than English have their owncommon names for Z. mauritiana (Pareek1983).

TaxonomyThe genus Ziziphus Mill. belongs to thefamily Rhamnaceae which contains about50 genera and some 900 species (Watsonand Dallwitz 1995). Ziziphus consists ofabout 170 species (Liu and Cheng 1995),most of which are native to tropical andsubtropical regions of Africa, Eurasia,Australia and the Americas. Liu andCheng (1995) identified two sections.Members of Section Ziziphus are distin-guished by their glabrous leaves andshoots, their deciduous fruiting branch-lets, and are found mainly in temperateregions. Members of Section Perduranshave pilose leaves and shoots, persistentfruiting branchlets and occur mostly in the

tropics and subtropics. This Section wasfurther sub-divided into two seriesCymosiflorae and Thyrsiflorae on the basisof the type of inflorescence and the char-acteristics of the endocarp. Ziziphusmauritiana was included in the seriesCymosiflorae. The classification of Liu andCheng (1995) is apparently similar to thatof Schirarend (1991), who divided the ge-nus into three distinct groups of species onanatomical and biogeographical grounds.

Three members of the genus Ziziphusare currently found in Australia. Ziziphusquadrilocularis F.Muell. and Z. oenopoliaMill. (sometimes spelled Z. oenoplia, e.g.Brock 1993) are native to Australia. Theformer is endemic, occurring only in theNorthern Territory and the Kimberley Re-gion of Western Australia (Wheeler et al.1992) while the latter is found in Queens-land and the Top End of the Northern Ter-ritory (Forster 1991, Brock 1993) as well asin India, Sri Lanka and tropical Asia(Pareek 1983). Ziziphus mauritiana Lam.

is not native to Australia. The IndexKewensis assigns Z. mauritiana and Z.jujuba to the same species but Chatterjeeand Randhawa (1952) hold that the twoare distinct. There is also disagreementregarding the taxonomic affinities ofthe many domesticated varieties of theZ. mauritiana–Z. jujuba complex (Pareek1983).

DescriptionThe following description of Z. mauritianain Australia was compiled from Pareek(1983), Anderson (1993), Parsons andCuthbertson (1992) and personal observa-tions.

General descriptionZiziphus mauritiana grows as a shrub orsmall tree 6–8 m tall, with a canopy up to10 m in diameter. Large plants tend tohave only a few or a single main stem andare densely branched, with the outer endsof the branches often reaching down to theground (Figure 1). Smaller plants are gen-erally shrubbier (Figure 2). Branches arezig-zagged with a leaf and thorn at eachangle. The thorns are generally curvedand usually between 0.5 and 2 cm long.The bark on older and larger trunks andbranches is generally rough, dark, andsomewhat furrowed while the bark onyoung stems is often greenish, quitesmooth but covered with fine, short hairs.The leaves are alternate, oval to round,glossy green above, and pale beneath witha covering of fine white to rusty hairs.Flowers are arranged in cymes borne inthe axils of the leaves (Vashishtha andPareek 1979). Individual flowers are small(5–8 mm in diameter) and whitish to paleyellow. Each consists of five triangular

The Biology of Australian Weeds39. Ziziphus mauritiana Lam.

A.C. Grice, CSIRO Sustainable Ecosystems, Private Bag, PO Aitkenvale,Queensland 4814, Australia. Email: tony.grice@cse.csiro.au

Review

Figure 1. Large established Ziziphus mauritiana have spreading canopiesand usually one to three main stems.

Plant Protection Quarterly Vol.17(1) 2002 3

sepals and five membranous petals, en-closing five stamens and a two- or three-celled ovary with a short style that termi-nates in two or three stigmas. The ovarydevelops into a sub-globular drupaceousfruit with a single stone that contains usu-ally one, sometimes two or three seeds.When mature, the fruit is 2–5 cm in diam-eter and yellow or reddish (Figure 3). The

flesh of the fruit is pale coloured and pal-atable. Individual seeds of Z. mauritianaare oval-shaped, approximately 8 mmlong and weigh 46.9 ± 2.0 mg (mean ± s.e,n = 50) (Grice 1996, Figure 3).

Distinguishing Australian Ziziphus taxaThe three species of Ziziphus that arefound in Australia can be readily distin-

guished from one another.Ziziphus oenopolia has leavesthat are green on both upperand lower surfaces and its fruitis a 2-celled drupe of about 10mm diameter that is blackwhen ripe. It is a straggly shrubthat grows to a maximumheight of 3 m (Brock 1993).Ziziphus mauritiana and Z. quad-rilocularis have leaves that arewhite or rusty on the lower sur-face. The former produces a2-celled drupe that is yellow toreddish when ripe and 20–50mm diameter. The fruit of Z.quadrilocularis is 4-celled, red,purple or black when ripe and10–18 mm in diameter. It growsas a shrub or tree up to 12 mhigh in coastal vegetation andmonsoon vine thicket (Bentham1863, Wheeler et al. 1992). Allthree species have stipularspines though those of Z. quad-rilocularis tend to be less persist-ent than those of the other two.

Distinguishing Ziziphus fromother taxaZiziphus mauritiana is readilydistinguished from specieswith which it occurs in Aus-tralia, including other thorny,invasive shrubs of northernAustralia such as Prosopis spp.(mesquite), Acacia nilotica (L.)Willd. ex Delile (prickly acacia),A. farnesiana (L.) Willd. (mi-mosa bush) and Parkinsoniaaculeata L. (parkinsonia). Al-though each of these speciesalso has thorns, their leaves aredivided. They also have inflo-rescences characteristic of theirrespective families, with eitherglobular heads (Acacia spp.),cylindrical spikes (Prosopisspp.) or large, bright yellow in-dividual flowers (P. aculeata)and pod-type fruits. The wide-spread, native Petalostigmapubescens Domin. (quininetree), whose range overlapsthat of Z. mauritiana, bears a su-perficial resemblance to it, hav-ing glossy, round leaves, smallcream-coloured flowers andglobular, orange fruits, but itlacks thorns.

HistoryZiziphus spp., variously referred to Z.mauritiana or Z. jujuba, have long been val-ued because they produce nutritious fruitsunder arid and semi-arid conditions. Thespecies has been under cultivation inChina and India for perhaps 4000 yearsand it has been domesticated to the pointwhere several hundred varieties havebeen developed (Pareek 1983). In its ca-pacity as a horticultural plant it has beenspread widely around the world, mostnotably in tropical, sub-tropical and semi-arid Asia and northern Africa. The historyof this early spread has not been docu-mented.

Ziziphus mauritiana has been present inthe Australian region since the mid-1800s.A specimen tree was being grown in aNorth Adelaide garden in 1842 (Parsonsand Cuthbertson 1992) but it was not re-ported from northern Australia until 1863,when it was recorded on islands in theTorres Strait. The first herbarium speci-mens from Australia were collected in theTownsville region in 1916 (Parsons andCuthbertson 1992). It was probably intro-duced to northern Australia because of itshorticultural values under semi-arid andwet-dry tropical conditions. Many of thelocations where the plant currently occurswere early mining settlements in northernQueensland. The common name chineeapple probably derives from its associa-tion with Chinese gold diggers. There islittle or no information available on thegeographical origin of the Z. mauritianathat became naturalized in Australia, oron the history of infestations in differentareas. An early attempt was made to growthe species commercially near Kununurra(Noel Wilson, Agriculture WA, Kunun-urra, personal communication) and, morerecently, Z. jujuba was advocated as hav-ing potential for cultivation in semi-aridregions of Australia (Walker et al. 1990).

DistributionNativeThe long history of human exploitationand cultivation of Z. mauritiana means thatthere is some doubt as to the details of thenative range of this species. Hooker (1875)records that Z. jujuba occurs wild and is‘extensively cultivated… …throughoutIndia to Ceylon [Sri Lanka]’. Pareek (1983)reported that the native range of Z. jujubawas in ‘Burma and British India’. Ander-son (1993) states that Z. mauritiana is na-tive to southern Asia and eastern Africa.Parsons and Cuthbertson (1993) describethe species as being a native of ‘easternAfrica, the Indian Ocean islands andsouthern Asia’ and state that it ‘occursnaturally… throughout the Indian sub-continent and Sri Lanka… through Burma[Myanmar] into China’.

Figure 3. The seeds (bottom) of Ziziphusmauritiana are protected by a woody endocarp(centre) inside a fleshy fruit (top) thatpromotes dispersal by animals.

Figure 2. Smaller established Ziziphusmauritiana are usually erect, multi-stemmedshrubs.

4 Plant Protection Quarterly Vol.17(1) 2002

Introduced – worldwideZiziphus mauritiana has been dispersedvery widely as a result of its use for horti-culture. Pareek (1983) reported that it is orwas cultivated in Afganistan, Iran, Syria,Burma [Myanmar], Australia, the USA,Italy, France, Spain, Portugal and northAfrica. Many or all of the populations ofZ. mauritiana in east Africa (Zimbabwe,Mosambique) (Exell et al. 1966) and tropi-cal west Africa (Senegal, Sudan, Guinea,Cote d’Ivoire, Niger, Nigeria) (Hutchin-son and Dalziel 1958, Evrard 1960) arepossibly introduced. The species was in-troduced to the Philippines (Merrill 1912)and parts of the Caribbean region (Neth-erlands Antilles) (Boldingh 1913).

Introduced – AustraliaThere are numerous infestations of Z.mauritiana across northern Australia (Fig-ure 4). It is most common and widespreadin north Queensland, where infestationsare scattered across about 150 000 ha (Dale1981). Many of these are of low density. In1977 the species was reported as presentin seven of the 15 pastoral districts ofQueensland (Burke, Cook, Leichhardt,Mitchell, North Kennedy, Port Curtis,Wide Bay) (Kleinschmidt and Johnson1977), but mostly as widely scatteredpopulations. This was portrayed in a 1988distribution map, highlighting the factthat most infestations are in the vicinity oftowns that developed with mining in theearly 1900s (James 1995). These towns in-clude Chilligoe, Mungana, Croydon,Forsayth, Ewan, Woolgar, Mt. Surprise,Ravenswood, Cloncurry, Longreach,Bowen and Rockhampton. The species isespecially prevalent in the Townsville-Charters Towers district. A similar patternof occurrence is found in the NorthernTerritory, with infestations around AliceSprings and Darwin, in the upper part ofthe Daly River catchment near Katherine,in the Roper River catchment and at nu-merous other locations in the Top End.Some of these infestations consist of only afew scattered plants (Parsons andCuthbertson 1992; Andrew O’Farrell,NTDPIF, Alice Springs, personal commu-nication). The species also occurs in thevicinity of various townships in the northof Western Australia, including Broome,Derby, Kununurra and various Aborigi-nal communities in the Kimberley region(Noel Wilson, Agriculture WA, Kunun-urra, personal communication).

The current broad spread of Z. maurit-iana across northern Australia suggeststhat the species is capable of greatly ex-panding its range. Bioclimatic analysis us-ing CLIMEX (Peter Mackey, QueenslandDepartment of Natural Resources, Bris-bane, personal communication) indicatesthe species could expand its range to in-clude a large proportion of the wet-drytropics and semi-arid areas of northern

Figure 4. Ziziphus mauritiana is presently distributed in widely scatteredinfestations across northern Australia. After Parsons and Cuthbertson(1992), Thorp and Lynch (2000), Wilson, O’Farrell and Horrocks (personalcommunication).

Figure 5. Potential distribution of Ziziphus mauritiana in Australia asdetermined using the program CLIMEX (Mackey, QDNR, personalcommunication). The Ecoclimatic Index (EI) indicates climatic suitability.EI > 50 indicates a climate that is very favourable for long-term survival.

Australia. The model predicts a zone ofhigh potential abundance covering muchof eastern Queensland. Areas of lowerhabitat suitability are predicted to coverthe northern half of the Northern Terri-tory and the Kimberley coast of WesternAustralia (Figure 5). An independent pre-diction of the potential distribution of Z.mauritiana, developed using the climate-modelling program CLIMATE (Thorp andLynch 2000), yielded a broadly similarpattern. However, it suggested that therewas a lower probability of the species be-coming a problem in the Top End of theNorthern Territory and the northern Cape

York Peninsula, but a higher probabilityof infestations developing in north-west-ern South Australia (Thorp and Lynch2000). Both predictions of potential distri-bution should be interpreted with somecaution.

HabitatZiziphus mauritiana is widely spreadacross the sub-humid and semi-arid tropi-cal and sub-tropical regions of Australia.Average annual rainfall of this broad zoneranges from 470–1200 mm (James 1995).The species grows on a very wide varietyof soil types including cracking clays,

Plant Protection Quarterly Vol.17(1) 2002 5

solodic soils and deep alluvials (James1995). Especially in the drier parts of itsrange, Z. mauritiana grows best in wetterparts of the landscape, including riparianzones. Ziziphus mauritiana frequently oc-curs where the soil and/or vegetation hasbeen severely disturbed, for example, bymining, heavy grazing, tree clearing androad construction. However, the mecha-nisms underlying these associations havenot been elucidated so it is not possible toreadily discern the roles of habitat factors,exogenous disturbance and the history ofintroduction, naturalization and invasion(Grice et al. 2001).

Growth and developmentMuch of the literature on Z. mauritiana re-lates to its cultivation as a horticulturalspecies rather than to its behaviour as awild plant. This literature frequently re-fers to specific cultivars. Pareek (1983) listsat least 65 cultivars that are grown in In-dia. By contrast, there has been relativelylittle research on the species as a weed.

MorphologyToky and Bisht (1993) reported that theabove- and below-ground biomasses of6-year-old Z. mauritiana were approxi-mately 8.5 and 2.5 kg respectively, yield-ing a root:shoot ratio of approximately 0.3.However, these were plantation trees thathad been irrigated in their first year andthe technique of manually excavatingroots from the soil probably overlookedmany of the finer roots and so probablyunder-estimated the root:shoot ratio.

In a pot experiment in which neitherwater nor soil nutrients were limiting,90 day-old seedlings of Z. mauritiana hadshoots over 30 cm high, tap roots over 70cm long and total plant dry weights of 4–5g (Sellers 1996). By the time these plantswere 30 days old, they were able to sproutfollowing decapitation above the cotyl-edonary node (Sellers 1996). Seedlingsgrowing under field conditions typicallyexhibit much slower growth rates.

Throughout the life of the plant, thespecies is characterized by a marked ca-pacity to sprout following damage to theshoot, even if that damage involves com-plete removal of the shoot (Grice et al.1999). The zone from which sprouting oc-curs extends to about 20 cm below the soilsurface.

PerennationZiziphus mauritiana is a long-lived species.Individual plants can live for at leastseveral decades although there are no ac-tual measurements of age. Where infesta-tions have not been controlled mechani-cally or chemically, stands contain veryfew large standing dead individuals, evenwhere many large mature individuals arepresent. This suggests that many currentinfestations probably have not existed for

longer than the potential life span of theplant. Growth data from Lansdown Re-search Station (near Townsville, Queens-land) suggest that it would take approxi-mately 20 years for a plant to reach aheight of 350–400 cm, though considerablevariation around this value can be ex-pected as plants will no doubt grow fasteror slower depending on seasonal condi-tions and their position in the landscape(Grice unpublished, Figure 6).

PhysiologyThe capacity of Z. mauritiana to sprout fol-lowing complete removal of the shoot sug-gests that the species maintains substan-tial stores of non-structural carbohydratesin the root system, but these have not beenquantified. It is also recognized as beingsalt-tolerant to the point where it has beenidentified as having potential for the rec-lamation of saline soils (Pareek 1983). Re-search in Zimbabwe indicated that, al-though the species exhibits a capacity forosmotic adjustment to low levels of soilmoisture, it often avoids drought stress byaccessing water deep in the soil profile(Arndt et al. 2000).

Various medicinal benefits have beenattributed to preparations derived fromthe leaves, roots, bark or fruits of Ziziphusspp. but there has been no systematicanalysis of their biochemical basis (Pareek1983). A pentacyclic triterpenoid, zizy-beranalic acid, has been isolated from thebark and roots of Z. jujuba (Kundu et al.1989). Five peptide alkaloids, includingfrangulanine and adouétine, and thebenzylisoquinoline alkaloid, coclaurine,have been isolated from the bark of the

roots (Otsuka et al. 1974). The seeds of Z.jujuba contain the saponins, jujuboside Aand jujuboside B (Kawai et al. 1974).

PhenologyZiziphus mauritiana exhibits a distinct an-nual phenological cycle that is linked tothe wet-dry climate cycle of its northernAustralian range. In the Townsville re-gion, the plant begins to produce new foli-age in the latter months of the dry season(September–October) though the timing ofleaf initiation is somewhat variable, withearly rains promoting growth. Floweringbegins in January or February, fruit beginsto develop in large numbers in March, andripening occurs between May and June.Seed dispersal takes place between Julyand September. Leaf fall begins in theearly part of the dry season so that, fromMay until September, most plants havefew leaves and those that are retained aregenerally senescent (Figure 7). This gen-eral pattern may vary slightly, both geo-graphically across northern Australia andfrom year to year (Grice 1998). In northernIndia, leaf fall takes place toward the endof the dry season (between April andJune), new leaves are initiated with theadvent of the monsoon (July), and fruitsmature in February-April. The timing ofleaf production, leaf senescence and fruitmaturity vary across the Indian sub-conti-nent, with earlier fruit set where wintersare shorter and milder (Pareek 1983). Thespecific triggers for these phenologicalevents have not been examined in Aus-tralia but Pareek (1983) argues that thetiming of growth, flowering and fruit ma-turity are largely temperature dependent.

y = 11.701x + 1.4393R2 = 0.819

y = 21.045x - 73.075R2 = 0.9142

y = 24.444x - 120.37R2 = 0.9357

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20Age (years)

Hei

ght

(cm

)

Figure 6. Relationships between the age and height of Ziziphus mauritianaare based on measurements of height increments over a four-year period ofplants growing at Lansdown Research Station. Linear relationships for eachof three height classes were linked by interpolation. Height classes were:■■■■■ height <1 m; ¡ 1 m < height <2 m; ▲▲▲▲▲ height >2 m (Grice unpublished).

6 Plant Protection Quarterly Vol.17(1) 2002

ReproductionFloral biologyThe time required to reach reproductivematurity will vary depending on the envi-ronment in which the plant is growing.The relationship between plant size andreproductive maturity is such that plantsless than one metre high are unlikely toflower or set seed (Grice 1996). Growthdata from Lansdown Research Stationsuggest that it would typically take plants9 years to reach this size, though this esti-mate is based on the assumption thatgrowth rates recorded for plants up 100cm high are valid from the time seedlingsemerge from the soil (Figure 6, Grice un-published).

Insects are the main pollinators of flow-ers of Z. mauritiana. The stamens are at-tached to a nectar-producing disk andthe pollen itself is sticky. Flowering Z.mauritiana attract a high level of insect ac-tivity (Diptera, Coleoptera, Lepidopteraand Hymenoptera) (Pareek 1983). Largeshrubs can produce many thousands offlowers in a single season. Individualflowers are short-lived and many appearnot to be pollinated (Vashishtha andPareek 1979).

Seed productionThe number of seeds produced per plantincreases with increasing plant size.Plants between 1 and 2 m high were re-ported to produce on average less thanfive fruits per season whereas plants over2 m high averaged over 80 fruits per sea-son (Grice 1996). Individual large plantsmay produce 5000 or more fruits in a sin-gle season (Grice 1998). At one site, whereplants over 300 cm high made up less than4% of the total population, it was esti-

mated that this height class produced 60–90% of fruits (Grice 1998). Most fruits con-tain a single seed.

Seed dispersalOn a global scale, humans have been amajor dispersal agent of Z. mauritiana,transporting seeds to many parts of theworld for commercial or casual horticul-ture. Likewise, within Australia, humanshave played an important role in spread-ing this species, either directly or indi-rectly. At a national scale, direct humandispersal has probably played a key rolein the establishment of most infestationsthat exist today, with naturalization oc-curring locally from plants sown forcasual horticulture.

On the other hand, local dispersal hasbeen facilitated by the fact that the fleshyfruits of Z. mauritiana are consumed by avariety of animals and the seed is pro-tected by the woody endocarp. Becausethe fruits and the woody endocarp that itcontains are relatively large, some smalleranimals are probably not important dis-persal agents. This is true of birds that con-sume the flesh but either do not removethe fruit from the parent tree or simplydrop it beneath the canopy. Species thathave been observed to feed in this way in-clude pale-headed rosellas (Platycercusadscitus Latham) and red-winged parrots(Aprosmictus erythropterus Gmelin) (Grice,personal observation). Pied currawongs(Strepera graculina Shaw) and channel-billed cuckoos (Scythrops novaehollandiaeLatham) are relatively large birds that oc-cur within the current range of Z.mauritiana and may play a role in its dis-persal. Intact endocarps containing viableseeds have been removed from the drop-

pings of Australian bustards (Ardeotisaustralis J.E.Gray) (Grice, personal obser-vation). This species is capable of movinglong distances across areas that providepotential habitat for Z. mauritiana (March-ant and Higgins 1993). Emus (Dromaeusnovae-hollandiae Latham) can also be con-sidered as potential dispersers of Z.mauritiana, being capable of swallowingthe fruit whole and passing the endocarpsintact (Noble 1975).

In Australia, domestic, feral and nativemammals play a major role in dispersingseeds of Z. mauritiana. In the Townsville(north east Queensland) region, intactendocarps containing viable seeds havebeen collected from the dung of domesticcattle, feral pigs and the native agile wal-laby (Macropus agilis J.E.Gray). Cattle dis-perse very large numbers of seeds. Indi-vidual dung pats collected during thefruiting season from Lansdown ResearchStation, contained up to 240 intact endo-carps with an average of 17 endocarps perdung pat. This means that cattle could po-tentially disperse very large numbers ofviable seeds across any paddock that con-tains a seed source. New infestationscould develop when herds of cattle carry-ing large numbers of seeds are moved topaddocks that were formerly free of Z.mauritiana. Furthermore, large numbers ofcattle are often transported long distancesand animals carrying seed could therebyinitiate new infestations many hundredsof kilometres from a seed source (Grice1998). Cattle are likely to be the most im-portant dispersal agent wherever they arepresent.

Feral pigs harvest fruits either from theground or from low hanging branches.Significant numbers of intact endocarpscan be found in their droppings (Grice1998). Feral pigs can disperse seeds acrosscattle-proof fences. While feral pigs tendto remain within home ranges, these mayextend over more than 30 km2 (Caley 1997,Saunders and McLeod 1999) and someanimals do occasionally move several tensof kilometres (Saunders and Bryant(1988).

Physiology of seeds and germinationThe woody endocarp imposes dormancyon the seed that it encloses. Less than5% of fresh seeds that remain enclosedwithin the endocarp will germinate if thefruit has not been consumed by an animal.For seeds from which the endocarp hadbeen removed, germination percentagesincreased to 56% (Grice 1996). However,seeds from fruits that had been consumedby cattle or pigs yielded germinationpercentages around 70–90% even whenthey remained within the endocarp (Grice1996). Removal of the endocarp fromfruits that had been consumed by walla-bies resulted in increases in germinationfrom 7 to 46% (Grice 1996), implying that

0

50

100

150

200

250

O N D J F M A M J J A S

Rai

nfal

l (m

m)

BudsExpanding

Full leafBuds

Anthesis

InitiationMaturation

Dispersal

SenescenceLeaf fall

Fruit

Flowers

Leaves

Figure 7. The annual phenological cycle of Ziziphus mauritiana (after Grice1998).

Plant Protection Quarterly Vol.17(1) 2002 7

ingestion by wallabies does not greatly in-fluence germinability.

Soil stored seed has lower germin-ability than fresh seed and buried seed haslower germinability than surface storedseed (Grice 1996). Germination percent-ages of surface stored seed was 31% after6 months, and 20% after 12 months. Bur-ied seeds had germination of 7% after both6 and 12 months (Grice 1996).

Seedling establishmentIn spite of the species’ adaptations for ani-mal-aided dispersal, a large proportion ofseeds remain close to the parent plant.This is indicated by the distribution offreshly fallen fruits relative to the loca-tions of large fruit-producing plants. Atthe time of fruit fall, there was an averageof 158 (s.d. = 134) fruits m-2 on the soil sur-face beneath the canopies of large plants(height between 230 and 450 cm) but only7 (s.d. = 5) m-2 in a one metre wide zonejust outside the drip line. At greater dis-tances from the drip line there were fewerthan 0.05 fruits m-2 (Grice 1996). Similarpatterns were documented for juvenile(height <1 m) plants. They were found ataverage densities of 0.45 m-2 beneath thecanopies of large trees, compared with<0.03 m-2 at distances more than 2 m fromthe drip line (Grice 1996).

The large size of the endocarp that en-closes the seeds of Z. mauritiana suggeststhat most seeds are likely to remain closeto the soil surface until they either germi-nate or die and decompose. At LansdownResearch Station, emergence has been ob-served following typical wet season rainsin January and February. These timingssuggest that germination can occur when-ever soil moisture levels are adequate butthe strongly summer-dominant rainfall ofnorthern Australia will dictate that mostgermination takes place between Decem-ber and March (Grice 1998). Four cohortsthat were monitored at Lansdown Re-search Station emerged in February 1995,January 1996, February 1997 and January1998 (Grice unpublished data)

Seedlings suffer high mortality ratesover their first dry season following emer-gence (Grice, 1998). All of the more than500 seedlings monitored in the February1995 and January 1996 cohorts mentionedabove died within 400 days of emergenceand less than 5% survived for more than150 days. These seedlings experiencedpoor wet seasons in 1995-1996 and 1996-1997. By contrast, 1.2% of the January 1998cohort survived for over 1000 days, and2.5% of the February 1997 cohort survivedfor at least 1400 days (Figure 8, Grice un-published data).

Population dynamicsAn understanding of the population dy-namics of naturalized populations of Z.mauritiana in Australia must be pieced

together from information that is availableon the history of its invasion, the growthand mortality rates of established plantsand patterns of seedling survival. The to-tal area currently occupied by Z. maurit-iana in Australia is surprisingly small(probably less than 200 000 ha; Dale 1981;Noel Wilson, AGWEST, Kununurra, per-sonal communication; Andrew O’Farrell,NTDPIF, Alice Springs, personal commu-nication) given the fact that the species hasbeen present in northern continental Aus-tralia at least since the early twentieth cen-tury. In comparison, rubber vine (Crypto-stegia grandiflora (Roxb.) R.Br.), which hasbeen in Australia for approximately thesame period of time, was estimated to bebroadly distributed across 350 000 km-2

(Humphries et al. 1991) and to heavily in-fest about 700 000 ha (Tomley 1995). Simi-larly, prickly acacia (Acacia nilotica), whichwas introduced to Australia in the 1890sand actively promoted as a shade and fod-der tree in the 1920s, covers more than7 000 000 ha (Mackey 1997). These com-parisons suggest that population growthrates of Z. mauritiana are relatively low.

Extrapolation from measured growthrates of individual Z. mauritiana indicatethat even in the climatically more favour-able portions of the species’ current Aus-tralian range, it takes 9–12 years for aplant to grow to a size where it is capableof producing even moderate numbers offruits in a season (Grice 1996). This ex-trapolation is supported by the few meas-urements that are available from seedlingsof known age. Five seedlings thatemerged in February 1997 averaged lessthan 10 cm high in December 2000 whenthey were approximately 4 years old.

Likewise, six seedlings that emerged inJanuary 1998 averaged less than 4 cm highwhen they were measured in December2000 at approximately 3 years old (Griceunpublished data). These low growthrates, combined with the species’ modestdispersal ability, explain why even after100 years in northern Australia, Z. maurit-iana remains somewhat patchily distrib-uted and apparently spreading out onlyslowly from the numerous sites at whichit was introduced. Especially in the drierparts of its introduced range, major re-cruitment events are likely to be episodicin response to wetter-than-average sea-sons (Archer et al. 1994, Grice et al. 1999).

ImportanceBeneficialIt is noteworthy that much of the literatureon Z. mauritiana relates to the species’value for horticulture, whether for com-mercial or casual purposes, most notablyon the Indian sub-continent. Pareek (1983)reports that, in India, it has conventionallybeen regarded as a ‘poor man’s fruit’. Thefruits are a rich source of vitamins C, Aand B and are used in a variety of ways.The wood is exploited for furniture andnumerous medicinal properties have beenattributed to various parts of the plant.In Australia, human exploitation of Z.mauritiana is largely restricted to casualharvesting of fruits from naturalized trees.Trees attributed to Z. jujuba have beengrown in an experimental orchard atMerbein, Victoria (Walker et al. 1990).

DetrimentalIt is perhaps only in Australia that the spe-cies has achieved overt status as a weed.

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200 1400Age (days)

% a

live

Figure 8. Survival (%) of seedlings of Ziziphus mauritiana that emerged atLansdown Research Station ●●●●● in February 1995, ■■■■■ January 1996, ▲▲▲▲▲ February1997 and ¡ January 1998 (Grice 1998, Grice unpublished).

8 Plant Protection Quarterly Vol.17(1) 2002

Ziziphus mauritiana has been associatedwith many of the deleterious effects thathave been linked to other exotic shrub spe-cies that invade extensive grazing lands orecologically similar areas that are used forother purposes. The species can form rela-tively dense thickets that are implicated inreducing livestock carrying capacitythrough loss of grass cover. However, thiseffect has not been quantified for Z.mauritiana. The same is true for other ef-fects that are generally associated with theinvasion of pastoral lands by woody spe-cies, such as impeding mustering and in-hibiting stock access to water. The species’thorny nature is another of its disadvan-tages.

Likewise, the environmental impacts ofZ. mauritiana have not been assessed. Thefact that native birds and mammals ex-ploit the fruits of this exotic shrub and socontribute to its dispersal indicates thatthe species has been incorporated into thefood webs of the ecosystems that it has in-vaded. Another example of this concernsthe use of the seeds of Z. mauritiana by thered-tailed black cockatoo (Calyptorhynchusbanksii Latham). Unlike other species thatexploit the flesh of the fruit, this bird spe-cifically targets the seeds contained withinthe woody endocarp, harvesting themfrom the plant, from the soil surface andfrom cattle dung (Grice 1996). In one sur-vey, an average of 34% and up to 65% offruits on individual trees were harvestedby black cockatoos. The species thus actsas a significant seed predator (Grice 1998).In many places where Z. mauritiana hasspread, it forms a shrub layer within for-merly open eucalypt woodlands. Else-where, it colonizes areas from which thenatural tree stratum has been cleared. Thespecies thus contributes to dramaticchanges in the structure of native vegeta-tion in northern Australia.

Actual and potential costs to Australia.The invasion of Australia by Z. mauritianais still in its early stages and, in manyplaces where it already occurs, infesta-tions are of low density, sometimes con-sisting of very scattered individuals. Totalloss of pastoral production, therefore, issmall compared with that attributed toother invasive shrubs in northern Aus-tralia, such as prickly acacia and rubbervine. There has, however, been no quanti-tative assessment of the losses due to Z.mauritiana. The main costs associated withthe presence of Z. mauritiana are those at-tributable to control activities. Should thepotential distribution of Z. mauritiana inAustralia be realized, the costs of controlwould increase accordingly.

LegislationZiziphus mauritiana is a declared plantthroughout Queensland where it is classi-fied P3, meaning that numbers and/or

distribution must be reduced throughoutthe state or parts thereof. Throughoutmost of the Northern Territory, the speciesis classified Class A and Class C, meaningthat the species cannot be introduced andmust be eradicated. The species is not adeclared weed in Darwin City, Palm-erston, Litchfield Shire and the AliceSprings region. It is a declared plant inWestern Australia, being classified P1 andP5 for the Kimberley Region, meaning, re-spectively, that it cannot be introducedand must be controlled on public lands. Inthe remainder of the state it is classified P1and so cannot be introduced. Z. mauritianais not a declared plant in other states (Par-sons and Cuthbertson 1992).

Weed managementControlling existing infestations of Z.mauritiana must depend almost entirely onmechanical and chemical techniques.Within each of these broad categoriesthere are several options available. Singletreatments are unlikely to eradicate an in-festation. The species’ seed dispersal abil-ity, seed longevity and sprouting capacitymean that, even when the best availabletechnique is applied, follow-up action willalways be required. Follow-up actionshould locate and treat any plants thatwere overlooked in a first pass, that recov-ered from the initial (or subsequent) treat-ment, or that emerged from soil storedseed or from seeds transported to the areaafter it was treated. Preventing spread atproperty, catchment and regional scales isalso vital.

HerbicidesSeveral registered chemicals are availablefor the control of Z. mauritiana in Aus-tralia. They can be effectively applied us-ing a range of application techniques.Triclopyr/picloram or triclopyr can be ap-plied as a basal bark spray to intact indi-vidual plants in a 1:60 herbicide:dieselmixture when the plants are activelygrowing. It is important that the mixturepenetrates all the crevices on each stem upto a height of 40 cm for stems of 15 cm di-ameter or less, but up to 100 cm for largerstems. Alternatively, the same herbicidemixtures can be applied to cut stumps atany time of year. Stumps should be cut asclose to the ground as possible and herbi-cides applied within 15 seconds (James1995). The method should give kill rates ofover 90% when used correctly. Obviously,both basal bark and cut stump applica-tions of herbicides require that plants betreated individually, and the use of eithertechnique can be made more difficult bythe spiny lower branches and the multi-stemmed character of many plants.

Triclopyr/picloram can also be appliedin a high volume spray mixture of 0.35 Lherbicide:100 L of water to treat activelygrowing regrowth. This treatment may be

most appropriate as a follow-up to me-chanical clearing of dense infestations.Soil application of picloram-triethanol-amine at 35–45 g m-2 can also be used totreat dense infestations, with the advan-tage that it is not necessary to treat plantsindividually. This treatment should be ap-plied prior to rain. The limitation of thistechnique is that it cannot be used in thevicinity of desirable trees or shrubs. Ageneral recommendation is that such re-sidual herbicides are not used within adistance of twice the height of desirabletrees (James 1995).

A trial conducted in north-easternQueensland examined the efficacy ofkarbutilate, tebuthiuron and hexazinone.To achieve 90% kill, 4 kg ha-1 and 16 kgha-1 of karbutilate were required on sandyloam and clay soils respectively. Similarpatterns were recorded with tebuthiuron,with 2.5 kg ha-1 and 3 kg ha-1 required onsandy loam and clay soils respectively.Hexazinone was not effective. Several ofthese treatments caused severe damage topastures (Bolton 1990).

Mechanical optionsMechanical treatment methods must takeinto account the capacity of Z. mauritianato sprout from the stem base. When theabove-ground portion of a plant is killedby either fire or mechanical treatment,sprouting occurs from undamagedmeristems in the below-ground portion.Generally, these meristems are locatedwithin 20 cm of the soil surface. For a me-chanical treatment to be effective, eitherthese meristems must be removed me-chanically or the mechanical treatmentmust be followed by herbicide applicationto the sprouting shoots. Z. mauritiana can-not be killed by breaking shoots off atground level.

Dense infestations can be bulldozedbut, unless the shoot is cut off at least 25cm below ground level, many individualswill sprout. A cutter bar or blade-ploughcan be used to cut plants off below groundlevel. It is necessary to check for regrowthafter an initial mechanical treatment andapply herbicides as a basal bark treatmentto any surviving plants (James 1995).

FireZiziphus mauritiana sprouts rapidly andvigorously after it has been burned. Veryfew plants are killed by fire. Mortality islargely restricted to plants that are lessthan 50 cm high at the time of the fire andeven for that height class mortality after asingle fire is less than 20% (Grice 1997).Mortality rates of larger plants after a sin-gle fire are much lower (<5%) (Grice 1997).Repeated burning has a greater impact onZ. mauritiana than a single fire. Five an-nual late-dry-season fires caused 44%mortality of plants that were under 1 mhigh, while three biennial late-dry-season

Plant Protection Quarterly Vol.17(1) 2002 9

fires caused 29% mortality. The sametreatments did not kill plants over 2 mhigh (Figure 9, Grice unpublished data).Fire does kill seeds of Z. mauritiana that areon the soil surface during a fire, with mor-tality rates of over 90% where the soil sur-face litter is consumed (Grice and Brown1996). Post-fire sprouting may be eitherfrom the base of the plant or from buds onthe trunk or branches. The position of theregrowth (i.e. whether from basal orcanopy sprouts) depends upon the inten-sity of the fire and the size of the plant atthe time of the fire. In general, plants un-der 150 cm high mostly sprout from basalmeristems whereas those over 150 cmhigh produce either only canopy sproutsor a combination of basal and canopysprouts (Grice 1997). Herbaceous fuelloads of the fires referred to here werearound 5000 kg ha-1 (Grice 1997).

These results suggest that there are nopractical fire regimes that will control ex-isting infestations of Z. mauritiana thoughannual burning may curtail recruitment.However, annual burning is unlikely to beacceptable from either commercial or en-vironmental perspectives. A major con-straint to using fire is fuel availability, andin pastoral areas, any destocking periodthat is required to facilitate the accumula-tion of fuel or allow pastures to recoverwill impose an economic cost (Grice 1997).

Grazing management systemsDomestic cattle are an important dispersalagent for Z. mauritiana (Grice 1996, 1998)so their management is important for re-tarding the invasion process. Cattle mobil-ity and paddock sizes in northern

Australia are such that, if a paddock con-tains both a seed source and cattle, Z.mauritiana has access to the entire paddockthrough cattle-aided dispersal. Thismeans that cattle-aided dispersal of seedsof Z. mauritiana cannot be managed atscales below the paddock level. On theother hand, cattle-aided dispersal be-tween paddocks can be managed by care-fully timing the movement of cattle. Cattleshould not be moved from infested pad-docks to weed-free paddocks when Z.mauritiana are fruiting. Alternatively, cat-tle that have had access to fruit of Z.mauritiana could be confined to a smallweed-free area, either holding yards or asmall holding paddock, before beingmoved to weed-free paddocks. The with-holding period would need to be 10 daysor more (Lunter 1988) to ensure that anyviable seeds had been voided. Moreover,any yards or holding paddocks that wereused in this way would have to be moni-tored for at least two years and any emerg-ing Z. mauritiana controlled.

Similar strategies should be applied tothe transport of cattle between properties.This should entail either not transportingcattle from areas where Z. mauritiana isfruiting, or imposing a 10-day withhold-ing period. Ideally, the withholding pe-riod should be imposed before the cattleleave an infested property so that both thetransport route and the destination prop-erty are protected. Vendor declarationsconcerning cattle access to fruits ofZ. mauritiana or other cattle-dispersedweeds, such as prickly acacia and mes-quite (Prosopis spp.) could be useful in thisregard.

Although the leaves of some Ziziphusspp., including Z. mauritiana are nutritiousfor livestock (Pareek 1983), it is unlikelythat they make a significant contributionto cattle diets or that browsing has a sig-nificant impact on the growth or survivalof established plants. On the other hand,there is the possibility that over-grazing ofperennial grasses would facilitate the pro-liferation of Z. mauritiana by freeing seed-lings from competition. In pot experi-ments, competition from the introducedstoloniferous Indian couch grass (Bothrio-chloa pertusa (L.) A.Camus) reduced bothgrowth and survival rates of seedlings ofZ. mauritiana (Sellers 1996).

Commercial exploitationAlthough Z. mauritiana is an importanthorticultural crop in many parts of south-ern Asia, especially India, the species isnot currently utilized commercially inAustralia. Some moves were made in theTownsville region to exploit the plant forwood chips and to this end special dispen-sation was provided by the QueenslandDepartment of Natural Resources to har-vest a declared plant. However, it seemsthat this effort has not been sustained. Onthe other hand, the fruits of Z. mauritianaare still casually exploited for their fruitthat are either eaten fresh or prepared asjams etc. This exploitation conceivablypresents some risk of spread of Z.mauritiana.

Natural enemiesNative insects. No published data areavailable on the native Australian insectsthat exploit Z. mauritiana.

Classical biological control. Biologicalcontrol of Z. mauritiana has not been at-tempted. The literature relating to insectsand pathogens that exploit the species hasbeen oriented to circumventing damage toplants cultivated for their fruits in Asia.Between them, Pareek (1983), Jothi andTandon (1995), Patil and Patil (1996) andVyas (1996) list at least 30 insect speciesthat feed on Z. mauritiana (Table 1). Thesecome from several insect Orders and feedon various parts of the host plant, includ-ing leaves, stems and fruits (Table 1). It isnot clear from these lists how host-specificthe various species are. Some, such as thefruit flies Dacus correctus Bezzi (=Bactroceracorrecta Bezzi) and D. dorsalis Hendel,are probably generalist feeders althoughCarpomyia vesuviana Costa is reported to bemonophagous (Sohi et al. 1990). A numberof insect species, and the mite Larvacarustransitans Ewing (Sharma 1992), do suffi-cient damage to cultivated plants to becommercially significant in India (Lakraand Singh 1983, Vyas 1996).

Various fungal pathogens have alsobeen reported as attacking Z. mauritiana inIndia. These include powdery mildew

0

20

40

60

80

100

94 95 96 97 98 99Year

Sur

viva

l (%

)

Figure 9. Survival (%) of Ziziphus mauritiana subjected to either annual orbiennial burning, or left unburned (Grice and Brown 1995, Grice 1997,Grice unpublished). o annually burned large plants, ¡ biennially burnedsmall plants, ▲▲▲▲▲ annually burnt small plants. ■■■■■ represents unburnt smalland large plants as well as biennially burned large plants each of whichsuffered no mortality. Small plants were <1 m high, large plants were >1 mhigh.

10 Plant Protection Quarterly Vol.17(1) 2002

Table 1. Insects and mites reported to feed on Ziziphus mauritiana in India.

Species Family: Order Impact

Larvacarus transitans Ewing Phytoptipalpidae: Acarina stem-gallingCassida sp. Chrysomelidae: Coleoptera leaf-feedingOocassida cruenta Fabr. Chrysomelidae: Coleoptera leaf-feedingCrinorrhinus crassirostris Faust Curculionidae: Coleoptera leaf-feedingMyllocerus Schönherr sp. Curculionidae: Coleoptera leaf-feedingXanthochelus superciliosus Curculionidae: Coleoptera leaf-feedingAdoretus pallens Semenov & Medvedev Coleoptera: Scarabaeidae leaf-feedingAdoretus versutus Harold Coleoptera: Scarabaeidae leaf-feedingHypothenemus areccae Hornung Scolytidae: Coleoptera stem-boringCarpomyia vesuviana Costa Tephritidae: Diptera fruit-feedingDacus dorsalis Hendel Tephritidae: Diptera fruit feedingDacus correctus Bezzi

(=Bactrocera correcta Bezzi) Tephritidae: Diptera fruit feedingMachaerota spp. Machaerotidae: Hemiptera sap-suckingPlanococcus citri Risso Pseudococcidae: Hemiptera sap-suckingPlanococcus lilacinus Ckll Pseudococcidae: Hemiptera sap-suckingNipaecoccus viridis Newstead Pseudococcidae: Hemiptera sap-suckingMacropulvinaria cf maxima Green Coccidae: Hemiptera sap-suckingDrepanococcus chiton Green Coccidae: Hemiptera sap-suckingSaissetia sp. Coccidae: Hemiptera sap-suckingMonosteria minutula Montandon Tingidae: Hemiptera sap-suckingPerissopneumom ferox Newstead Margarodidae: Hemiptera sap-suckingMaconellicoccus hirsutus Green Pseudococcidae: Hemiptera sap-suckingSystasis sp. Eulophidae: Hymenoptera leaf-feedingTonica ziziphi Stainton Oecophoriade: Lepidoptera leaf webberAchaea janata L. Limacodidae: Lepidoptera leaf-feedingIndarbela quadrinotata Walker Metarbelidae: Lepidoptera bark-feedingTarucus theophrastus Fabricius Lycaenidae: Lepidoptera leaf-feedingLycaenids sp. Lycaenidae: Lepidoptera leaf-feedingEuproctis fraterna Moore Lymantriide: Lepidoptera leaf/fruit feedingThiacidas postica Walker Noctuidae: Lepidoptera leaf-feedingMeridarchis scyrodes Meyrick Carposonidae: Lepidoptera fruit-borerFlorithrips traegardhi Trybom Thriptidae: Thysanoptera leaf-feeding

(Oidium sp.), sooty mould (Cladosporiumzizyphi P. Karst and Roun., Cercospora spp.,Isariopsis indica var. zizyphi P.C.Gupta andMadaan, and the leaf rust Phakopsorazizyphi-vulgaris (Henn.) Dietel (Morton1987). The continued interest in Ziziphusspp. for commercial fruit production inAustralia may counter any considerationof the potential for biological control.

Strategic managementThe control of Z. mauritiana must rely moststrongly on the use of chemical and me-chanical techniques to treat existing infes-tations and on property, catchment andregional hygiene protocols and practicesto minimize the risk that new infestationswill develop. The character of land useacross the current and potential range ofZ. mauritiana in Australia dictates that, inmost areas, the resources available to con-trol species like Z. mauritiana will alwaysbe very limited relative to the size of theproblem. This demands an efficiency ofcontrol effort. Particular infestationsshould be treated using the most appro-priate technique or integrated combina-tion of techniques. On the other hand, thecase of Z. mauritiana is made somewhatmore tractable that it would otherwise beby the apparently relatively slow rates of

spread and population increase.Actions to counter Z. mauritiana should

be strategically organized, meaning thatappropriate measures should be appliedat times and places that gain the greatestbenefit for the costs involved (Grice 2000).An important component of a strategymust be practices and protocols for mini-mizing the risk of cattle-aided transport ofseed. Movement of cattle should be timedto avoid the main fruiting period of Z.mauritiana or cattle should be withheld inyards or holding paddocks until they areseed-free. At the property level, infesta-tions should be prioritized for treatment.Paddocks that have only a few Z. maurit-iana should be treated as highest priority.If resources are not available to treat all theplants in a paddock at the one time, effortshould be concentrated on the largest in-dividuals to more effectively reduce thetotal seed output of the infestation. Withina paddock, outlying, isolated individualsmay not be any more important than cen-tral individuals in contributing to popula-tion increase (Grice 1998). Managersshould be alert for the forerunners of newinfestations in previously clean paddocksand treat them as soon as they are located.

At the catchment scale, some popula-tions, because of their size, structure, fe-

cundity or location, may be more likelythan others to expand or contribute to theestablishment of new infestations (Grice1998). For example, large healthy indi-viduals growing in a riparian zone willprobably be more significant than indi-viduals growing in upland areas becauseof their more prolific seed production, thepossibility of down-stream transport ofseeds, and the concentration of cattle inlower parts of the landscape. Likewise,upstream infestations should be given pri-ority over downstream infestations.

AcknowledgmentsI thank Noel Wilson (AGWEST, Kunun-urra), Andrew O’Farrell (Weeds Branch,NT Department of Primary Industries andFisheries, Alice Springs) and PaulHorrocks (QDNR, Charters Towers) forinformation on the distribution of Z.mauritiana in Western Australia, theNorthern Territory and Queensland re-spectively. Peter Mackey (Queensland De-partment of Natural Resources, Brisbane)provided the CLIMEX map of the poten-tial distribution of Z. mauritiana. CathyLockett helped compile a list of insects re-ported from Z. mauritiana and, along withIan Radford and Dane Panetta, providedhelpful comments on a draft manuscript.

ReferencesAnderson, E. (1993). ‘Plants of central

Queensland’. (Queensland Departmentof Primary Industries, Brisbane).

Archer, S. (1994). Woody plant encroach-ment into southwestern grasslands andsavannas: rates, patterns and proxi-mate causes. In ‘Ecological implicationsof livestock herbivory in the West’, edsM. Vavra, W. Laycock, and R. Peiper,pp. 13-68. (Society for Range Manage-ment, Denver, Colorado).

Arndt, S.K., Wanek, W., Clifford, S. andPopp, M. (2000). Contrasting adapta-tions to drought stress in field-grownZiziphus mauritiana and Prunus persicatrees: water relations, osmotic adjust-ment and carbon isotope composition.Australian Journal of Plant Physiology 27,985-96.

Bentham, G. (1863). ‘Flora Australiensis: adescription of the plants of the Austral-ian Territory’. (Lovell Reeve and Co.,London).

Boldingh, I. (1913). ‘Flora voor de Neder-landsch West-Indische Eilanden’.(Druk van J.H. de Bussy, Amsterdam).

Bolton, M.P. (1990). Control of chinee ap-ple, Ziziphus mauritiana, with residualherbicides. Proceedings of the 9th Aus-tralian Weeds Conference, pp. 403-6.

Brock, J. (1993). ‘Native plants of northernAustralia’. (Reed, Chatswood).

Caley, P. (1997). Movements, activity pat-terns and habitat use of feral pigs in atropical habitat. Wildlife Research 24,77-87.

Plant Protection Quarterly Vol.17(1) 2002 11

Chatterjee, D. and Randhawa, G.S. (1952).Standardised names of cultivatedplants in India. 1. Fruits. Indian Journalof Horticulture 9, 24-36.

Dale, I. (1981). Chinee apple (Ziziphusmauritiana) in north Queensland. Inter-nal Report, Biological Section, Queens-land Department of Lands, Sherwood.

Evrard, C. (1960). Rhamnaceae. Comiteexecutif de la Flore du Congo Belge etle Jardin Botanique de l’Etat. Flore duCongo Belge et du Ruanda-Urundi.Publications de L’Institute Nationalpour L’Etude Agronomique du CongoBelge IX, Bruxelles, pp. 429-52.

Exell, A.W., Fernandes, A. and Wild, H.(1966). ‘Flora Zambesiaca: Mozam-bique, Malawi, Zambia, Rhodesia,Bechuanaland Protectorate’, Volume 2,Part 2. (Crown Agents for OverseaGovernments and Administrations,London).

Forster, P.I. (1991). Zizyphus oliganthaMerr. & Perry is a synonym of Z.oenopolia (L.) Mill. (Rhamnaceae).Austrobaileya 3, 563-4.

Grice, A.C. (1996). Seed production, dis-persal and germination in Cryptostegiagrandiflora and Ziziphus mauritiana, twoinvasive shrubs in tropical woodlandsof northern Australia. Australian Journalof Ecology 21, 324-31.

Grice, A.C. (1997). Post-fire regrowth andsurvival of the invasive tropical shrubsCryptostegia grandiflora and Ziziphusmauritiana. Australian Journal of Ecology22, 49-55.

Grice, A.C. (1998). Ecology in the manage-ment of invasive rangeland shrubs: acase study of Indian jujube (Ziziphusmauritiana). Weed Science 46, 467-74.

Grice, A.C. (2000). Weed management inAustralian rangelands. In ‘Australianweed management systems’, ed. B.M.Sindel, pp. 429-58. (R.G. and F.J.Richardson, Melbourne)

Grice, A.C. and Brown, J.R. (1996). Fireand the population ecology of invasiveshrubs in the tropical woodlands. In‘Frontiers of population ecology’, edsR.B. Floyd, A.W. Sheppard and P.J. DeBarro, pp. 589-97. (CSIRO, Canberra).

Grice, A.C., Radford, I.J., and Abbott,B.N. (2001). Regional and landscape-scale patterns of shrub invasion intropical savannas. Biological Invasions 2,187-205.

Grice, A.C., Walker, L., and Whiteman, L.(1999). An invasive rangeland shrubresponds rapidly to top removal. In‘People and rangelands: building thefuture’, Proceedings of the VI Interna-tional Rangeland Congress Inc.,Townsville, eds D. Eldridge and D.Freudenberger, pp. 591-3.

Hooker, J.D. (1875). ‘The flora of BritishIndia, Volume 1, Ranunculaceae toSapindaceae’. (L. Reeve and Co.Ashford, England).

Humphries, S.E., Groves, R.H., andMitchell, D.S. (1991). Plant invasions ofAustralian ecosystems: a status reviewand management directions. Kowari 2,1-116.

Hutchinson, J. and Dalziel, J.M. (1958).‘Flora of west tropical Africa’, Volume1, Part 2. (Crown Agents for OverseaGovernments and Administrations,London).

James, P. (1995). Chinee apple. In ‘Exoticwoody weeds and their control in northwest Queensland’, ed. N. March, pp.37-9. (Queensland Department ofNatural Resources, Cloncurry).

Jothi, B.D. and Tandon, P.L. (1995).Present status of insect pests of ber inKarnataka. Current Research, Universityof Agricultural Sciences 24, 153-5.

Kawai, K., Akiyama, T., Ogihara, Y., andShibata, S. (1974). A new sapogenin inthe saponins of Ziziphus jujuba, Hoveniadulcis and Bacopa monniera. Phytochem-istry 13, 2829-32.

Kleinschmidt, H.E. and Johnson, R.W.(1977). ‘Weeds of Queensland’.(Queensland Government Printer, Bris-bane).

Kundu, A.B., Mondal, D.N., Dey, A.K. andBanerji, A. (1989). Zizyberanalic acid, apentacyclic triterpenoid of Zizyphusjujuba. Phytochemistry 28, 3155-8.

Lakra, R.K. and Singh, Z. (1983). Oviposi-tion behaviour of ber fruitfly, Carpomyiavesuviana Costa and relationship be-tween its incidence and ruggedness infruits in Haryana. Indian Journal of Ento-mology 45, 48-59.

Liu, M.J. and Cheng, C.Y. (1995). A taxo-nomic study on the genus Ziziphus.Acta Horticulturae 390, 161-5.

Lunter, M.G. (1988). ‘The role of cattle inthe spread of chinee apple (Ziziphuzmauritiana)’. (University of Wagenin-gen, The Netherlands).

Mackey, A.P. (1997). The biology of Aus-tralian weeds 29. Acacia nilotica ssp.indica (Benth.) Brenan. Plant ProtectionQuarterly 12, 7-17.

Marchant, S. and Higgins, P.J. (1993).‘Handbook of Australian, New Zea-land and Antarctic birds, Volume 2,Raptors to Lapwings’, pp. 636-47. (Ox-ford University Press, Melbourne).

Merrill, E.D. (1912). ‘A flora of Manila’.(Department of the Interior, Bureau ofScience, Manila).

Morton, J. (1987). ‘Fruits of warm cli-mates’. (Julia Morton, Miami, Florida).

Noble, J.C. (1975). The effects of emus(Dromaius novaehollandiae Latham) onthe distribution of the nitre bushNitraria billardieri DC. Journal of Ecology63, 85-118.

Otsuka, H., Ogihara, Y. and Shibata, S.(1974). Isolation of coclaurine fromZizyphus jujuba by droplet counter-cur-rent chromatography. Phytochemistry13, 2016.

Pareek, O.P. (1983). The Ber. (IndianCouncil of Agricultural Research, NewDehli).

Parsons, W.T. and Cuthbertson, E.G.(1992). ‘Noxious weeds of Australia’.(Inkata Press, Melbourne).

Patil, P. and Patil, B.V. (1996). Insect pestsof ber in North Karnataka. South IndianHorticulture 44, 113.

Saunders, G. and Bryant, H. (1988). Theevaluation of a feral pig eradicationprogram during a simulated exotic dis-ease outbreak. Australian Wildlife Re-search 15, 73-81.

Saunders, G. and McLeod, S. (1999). Pre-dicting home range size from the bodymass or population densities of feralpigs, Sus scrofa (Artiodactyla: Suidae).Australian Journal of Ecology 24, 538-43.

Schirarend, C. (1991). The systematicwood anatomy of the Rhamnaceae Juss.(Rhamnales). 1. Tribe Zizipheae. IAWABulletin 12, 359-88.

Sellers, E.A. (1996). Responses of chineeapple (Ziziphus mauritiana Lamk.) tocompetition and decapitation. HonoursThesis, James Cook University,Townsville.

Sharma, A. (1992). Seasonal incidence ofLarvacarus transitans on Zizyphus inRajasthan. Annals of the Arid Zone 31,231-2.

Sohi, A.S., Sohi, A.S. and Sandhu, G.S.(1990). Unusual occurrence of Carpomyiavesuviana Costa during monsoon in thePunjab. Journal of Insect Science 3, 188.

Thorp, J.R. and Lynch, R. (2000). The de-termination of weeds of national sig-nificance. (National Weeds Strategy Ex-ecutive Committee, Launceston).

Toky, O.P. and Bisht, R.P. (1993). Above-ground and below-ground allocation inimportant fuelwood trees from aridnorth-western India. Journal of Arid En-vironments 25, 315-20.

Tomley, A.J. (1995). The biology of Aus-tralian weeds 26. Cryptostegia grandi-flora R.Br. Plant Protection Quarterly 10,122-30.

Vashishtha, B.B. and Pareek, O.P. (1979).Flower morphology, fruit set and fruitdrop in some ber (Zizyphus mauritiana)cultivars. Annals of Arid Zone 18, 165-9.

Vyas, H.N. (1996). Pest complex ofZizyphus mauritiana Lamark. Crop Re-search 11, 216-8.

Walker, R., Sykes, S. and Possingham J.(1990). Fruit crops with potential inAustralia: the Chinese date. Agricul-tural Science 3, 35-7.

Watson, L. and Dallwitz, M.J. (1995). Thefamilies of flowering plants: descrip-tions and illustrations. URL http://muse.bio.cornell.edu/delta/rhamnaceae.

Wheeler, J.R., Rye, B.L., Koch, B.L., andWilson, A.J.G. (1992). ‘Flora of the Kim-berley region’. (Department of Conser-vation and Land Management, Como,Western Australia).