Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Rubus armeniacus
(Himalayan blackberry)

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Datasheet

Rubus armeniacus (Himalayan blackberry)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Rubus armeniacus
  • Preferred Common Name
  • Himalayan blackberry
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • R. armeniacus is a perennial shrub native to Armenia. It was introduced outside of its native range as a cultivated crop for the production of sweet fruits. It soon escaped cultivation and has since naturalized...

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Pictures

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PictureTitleCaptionCopyright
Rubus armeniacus (Himalayan blackberry); fruits and foliage. Oregon, USA. July, 2004.
TitleFruits and foliage
CaptionRubus armeniacus (Himalayan blackberry); fruits and foliage. Oregon, USA. July, 2004.
Copyright©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); fruits and foliage. Oregon, USA. July, 2004.
Fruits and foliageRubus armeniacus (Himalayan blackberry); fruits and foliage. Oregon, USA. July, 2004.©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); infestation, showing flowers and foliage. Oregon, USA.
TitleInfestation
CaptionRubus armeniacus (Himalayan blackberry); infestation, showing flowers and foliage. Oregon, USA.
Copyright©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); infestation, showing flowers and foliage. Oregon, USA.
InfestationRubus armeniacus (Himalayan blackberry); infestation, showing flowers and foliage. Oregon, USA.©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); infestation. USA.
TitleInfestation
CaptionRubus armeniacus (Himalayan blackberry); infestation. USA.
Copyright©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); infestation. USA.
InfestationRubus armeniacus (Himalayan blackberry); infestation. USA.©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); foliage and canes. Georgia, USA.
TitleFoliage and canes
CaptionRubus armeniacus (Himalayan blackberry); foliage and canes. Georgia, USA.
Copyright©Karan A. Rawlins/University of Georgia/Bugwood.org - CC BY-NC 3.0 US
Rubus armeniacus (Himalayan blackberry); foliage and canes. Georgia, USA.
Foliage and canesRubus armeniacus (Himalayan blackberry); foliage and canes. Georgia, USA.©Karan A. Rawlins/University of Georgia/Bugwood.org - CC BY-NC 3.0 US
Rubus armeniacus (Himalayan blackberry); flowers and foliage. Oregon, USA. June, 2005.
TitleFlowers and foliage
CaptionRubus armeniacus (Himalayan blackberry); flowers and foliage. Oregon, USA. June, 2005.
Copyright©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); flowers and foliage. Oregon, USA. June, 2005.
Flowers and foliageRubus armeniacus (Himalayan blackberry); flowers and foliage. Oregon, USA. June, 2005.©Eric Coombs/Oregon Department of Agriculture/Bugwood.org - CC BY 3.0 US
Rubus armeniacus (Himalayan blackberry); seeds from fruits. Note scale. USA.
TitleSeeds
CaptionRubus armeniacus (Himalayan blackberry); seeds from fruits. Note scale. USA.
Copyright©Julia Scher/Federal Noxious Weeds Disseminules/USDA APHIS ITP/Bugwood.org - CC BY-NC 3.0 US
Rubus armeniacus (Himalayan blackberry); seeds from fruits. Note scale. USA.
SeedsRubus armeniacus (Himalayan blackberry); seeds from fruits. Note scale. USA.©Julia Scher/Federal Noxious Weeds Disseminules/USDA APHIS ITP/Bugwood.org - CC BY-NC 3.0 US

Identity

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Preferred Scientific Name

  • Rubus armeniacus Focke

Preferred Common Name

  • Himalayan blackberry

Other Scientific Names

  • Rubus discolor Weihe and Nees
  • Rubus hedycarpus subsp. armeniacus (Focke) Erichsen
  • Rubus macrostemon f. armeniacus (Focke) Sprib.
  • Rubus procerus auct. PJ Müll. ex Boulay

International Common Names

  • English: Armenian blackberry; Himalaya berry; Himalayan giant blackberry
  • French: ronce d'arménie

Local Common Names

  • Czech Republic: ostružník sladkoplodý
  • Denmark: armensk brombær
  • Finland: armeniankarhunvatukka
  • Germany: armenische Brombeere; armenische Brombeere; Gartenbrombeere; himalaya Brombeere
  • Italy: rovo a peli rossi
  • Netherlands: dijkviltbraam
  • Poland: jezyna kaukaska
  • Sweden: armeniskt björnbär

Summary of Invasiveness

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R. armeniacus is a perennial shrub native to Armenia. It was introduced outside of its native range as a cultivated crop for the production of sweet fruits. It soon escaped cultivation and has since naturalized in many temperate areas around the world. R. armeniacus can reproduced both vegetatively and by the production of seed, which can be transported to new locations after ingestion by birds. This species is highly invasive and can form impenetrable thickets which have a negative impact on native flora and fauna. A PIER risk assessment gave this species a high risk score of 24 (PIER, 2015). In addition to this, it has been reported as highly invasive in Central Europe (von Raab-Straube and Raus, 2015) and has been identified as one of the 10 most problematic invasive plants or bryophytes in Sweden (Torbjorn et al., 2015) and noted as a threat to vegetation in Pannonian sandy habitats in Hungary (Király et al., 2014).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Rosales
  •                         Family: Rosaceae
  •                             Genus: Rubus
  •                                 Species: Rubus armeniacus

Notes on Taxonomy and Nomenclature

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The Rubus genus is large and very complex consisting of more than 750 species. The occurrence of polyploidy, hybridization and apomixis all contribute to the huge complexity of its taxonomy. R. armeniacus is considered to be a member of the broad R.fruticosus L. aggregate.

R. armeniacus has two frequently used, but incorrect, synonyms that cause much confusion, R. procerus and R. discolorR. procerus is not a valid name for R. armeniacus, but rather a synonym of R. praecox (Ceska, 1999; The Plant list, 2013; USDA-ARS, 2015). An explanation for this confusion is that R. armeniacus has been mistaken for R. praecox and thus confused for R. procerus (Jones, 2004). Similarly, R. discolor is not a valid name for R. armeniacus and is in fact a synonym of R. ulmifolius (Ceska, 1999; The Plant List, 2013; Spjut, 2015). With much of the taxonomic confusion found in literature referring to Rubus species found in North America, Ceska (1999) cites two botanists specializing in Rubus species, J Holub and HE Weber. Both these botanists support that the two synonyms are not valid, noting that R. praecoxand R. ulmifolius are two species endemic to Europe.

The consequence of the common erroneous usage of both R. procerus and R. discolor is that much of the information in the literature on R. armeniacus is confounded by voluminous references to the above two ‘synonyms’. For example, R. discolor has been incorrectly declared a weed or noxious weed in a number of states in the USA (USDA-ARS, 2015) and numerous academic publications refer to the three Rubus species as synonyms (e.g. Caplan and Yeakley 2006; Clark and Jasiekuk, 2012). Many publications also use the common name Himalayan blackberry when referring to both R. discolor and R. armeniacus.

It is also sometimes unclear in the literature whether the authors are referring to R. armeniacus or other closely related taxa (Francis, 2014). For example, R. armeniacus is sometimes mistakenly referred to as R. frucitosus when it is only one of several species composing the R. frucitosus aggregate (Jones, 2004).

Much of the information in this datasheet is sourced from publications that explicitly specify R. armeniacus but in some cases information pertaining to R. discolor when referred to as Himalayan blackberry or a synonym of R. armeniacus is used.

Description

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R. armeniacus is a perennial woody shrub in which individual canes can reach 6-12 m horizontally and 3 m vertically. Leaves are toothed and typically compounded with five leaflets but atypically or on fruiting branches can be tri- or unifoliate. Leaf blades are 3-12 cm long, ovate to orbicular and dark green in colour. Flowers are white to rose coloured and have five transversely arranged petals. The flowers form in groups of three to 20 in terminal panicles. The fruit are less than 2 cm aggregates of black, shiny, roundish drupelets. Each drupe contains a single, hard, flattened seed (Soll, 2004; Francis, 2014; Ensley, 2015).

Plant Type

Top of page Broadleaved
Perennial
Seed propagated
Shrub
Vegetatively propagated
Woody

Distribution

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R. armeniacus is present in parts of Eurasia and is considered as native only to Armenia and possibly also northern Iran. It has become widely cultivated and naturalized in many parts of the world. It is established or naturalized along the Western and East-Central USA: from California to British Colombia on the West Coast and middle sections in the east, from Delaware to Virginia. It is also reported to be well established in Hawaii and much of central and western Europe (Francis, 2014). It is reported to be naturalized and one of the most common blackberry species in several Western European countries including Germany and the Netherlands. Ceska (1999) reports that it is a common garden escape in nearly all European countries. It is noted that the species is still spreading in Europe and there has been some speculation that it has potential to become invasive in this region (Allen 2003; Loos and Keil, 2006).

The species has been reported as present in Australia, New Zealand and South Africa (Francis, 2014). This has been confirmed for New Zealand, however, its presence in Australia and South Africa is contested due to taxonomic confusion. It is possible that the species is not present and has been mistakenly referred to as R. frucitosus as it belongs to the R. frucitosus aggregate, or as in the USA, the species has been mistaken for R. procerus. In Australia, species from the R.fruticosus aggregate are present and recognized as invasive but R. armeniacus has not been recognized as a species from this group of national significance (NSW Department of Primary Industries Weed Management Unit, 2009). This is also the case in South Africa (Molewa, 2014). Evans and Weber (2003) recently identified the R. fruticosus aggregate in Australia as a biotype of R. anglocandicans. The authors provide a full description and illustration of R. anglocandicans and assert that it is separate from R. armeniacus and that R. armeniacus has not in fact been recorded present in Australia.

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.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

ArmeniaPresentNative Not invasive USDA-ARS, 2015

Africa

South AfricaPresentIntroducedFrancis, 2014

North America

CanadaPresentIntroduced Invasive USDA-NRCS, 2015
-British ColumbiaPresentIntroduced Invasive ISSG, 2015
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroduced Invasive USDA-NRCS, 2015
-AlaskaPresentIntroduced Not invasive Klein, 2011Pacific Maritime
-ArizonaPresentIntroduced Invasive USDA-NRCS, 2015
-ArkansasPresentIntroduced Invasive USDA-NRCS, 2015
-CaliforniaPresentIntroduced Invasive USDA-NRCS, 2015
-ColoradoPresentIntroduced Invasive USDA-NRCS, 2015
-DelawarePresentIntroduced Invasive USDA-NRCS, 2015
-HawaiiPresentIntroduced Invasive PIER, 2015Reported as R. discolor (synonym of R. armeniacus) on Maui and Oahu Islands
-IdahoPresentIntroduced Invasive USDA-NRCS, 2015
-IllinoisPresentIntroduced Invasive USDA-NRCS, 2015
-KentuckyPresentIntroduced Invasive USDA-NRCS, 2015
-MassachusettsPresentIntroduced Invasive USDA-NRCS, 2015
-MissouriPresentIntroduced Invasive USDA-NRCS, 2015
-MontanaPresentIntroduced Invasive USDA-NRCS, 2015
-NevadaPresentIntroduced Invasive USDA-NRCS, 2015
-New JerseyPresentIntroduced Invasive USDA-NRCS, 2015
-New MexicoPresentIntroduced Invasive USDA-NRCS, 2015
-OhioPresentIntroduced Invasive USDA-NRCS, 2015
-OregonPresentIntroduced Invasive USDA-NRCS, 2015
-PennsylvaniaPresentIntroduced Invasive USDA-NRCS, 2015
-TennesseePresentIntroduced Invasive USDA-NRCS, 2015
-UtahPresentIntroduced Invasive USDA-NRCS, 2015
-VirginiaPresentIntroduced Invasive USDA-NRCS, 2015
-WashingtonPresentIntroduced Invasive USDA-NRCS, 2015

Europe

Bosnia-HercegovinaPresentIntroduced Invasive Raab-Straube and Raus, 2015
Czech RepublicIntroduced Invasive Trávnícek and Zázvorka, 2005Naturalized
DenmarkPresentIntroduced Not invasive European Botanic Gardens Consortium, 2014
FrancePresentIntroduced Not invasive Mercier, 2012
GermanyPresentIntroducedKollmann, 1998Recorded as potentially invasive
HungaryPresentIntroducedKirály et al., 2014Recorded as potentially invasive
IrelandPresentIntroduced Not invasive Allen, 2003
ItalyPresentIntroduced Not invasive Hammer et al., 2004
MacedoniaPresent Not invasive Cvetkovic and Rizovski, 1973Reported as R. discolor (synonym of R. armeniacus)
NetherlandsPresentIntroduced Not invasive Haveman et al., 2014
NorwayPresentIntroducedGederaas L Salvesen I Viken A, 2007Recorded as potentially invasive
PolandPresentIntroduced Not invasive Boratyn'ska, 1995
SlovakiaPresentIntroduced Not invasive European Botanic Gardens Consortium, 2014
SwedenPresentIntroducedTorbjorn et al., 2015Recorded as potentially invasive
SwitzerlandPresentIntroduced Invasive Wittenberg, 2005
UKPresentIntroduced Not invasive Allen, 2003Noted as aggressive, common and increasing rapidly

Oceania

AustraliaPresentIntroducedFrancis, 2014Contested by Evans and Weber, 2003
-QueenslandPresentIntroduced Invasive PIER, 2015
-South AustraliaPresentIntroducedAtlas of Living Australia, 2015
-TasmaniaPresentIntroducedAtlas of Living Australia, 2015
New ZealandPresentIntroducedFrancis, 2014

History of Introduction and Spread

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R. armeniacus is not from the Himalayas as the common name would suggest, rather it originates from Eurasia and is considered to be native only to Armenia. It was first introduced beyond its native range for its tasty fruits. In 1835 it was introduced to Germany by Booth, who named it R. fruticosus fr. maximo and it became the most frequently cultivated blackberry in Europe. It was first introduced to North America by Luther Burbank in 1885 and to New Zealand and Australia before 1885 (Ceska, 1999). The species is a common garden escape with dispersal aided by water, birds and small mammals.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Canada USA 1945 Escape from confinement or garden escape (pathway cause) Yes Ensley (2015)
Germany Armenia 1835 Horticulture (pathway cause) Yes Ceska (1999) First introduced by Booth
USA 1885 Horticulture (pathway cause) Yes Ceska (1999) First introduced by Luther Burbank

Risk of Introduction

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This species and many other blackberry species are well recognized as problematic across the globe. R armeniacus was intentionally introduced into a number of areas for its production of fruits where it has since escaped cultivation. This species has received a high risk score by PIER, (2015) and features on a number of national and regional invasive species lists, including in North America. Anecdotal and official awareness of the risks will likely limit the risk of further introduction. Nevertheless, this species can produce a large number of seeds which are readily dispersed into new areas by water, birds and small mammals and can also spread locally by vegetative growth.

Habitat

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R. armeniacus occurs mainly in areas with an average annual rainfall greater than 760 mm, at altitudes from near sea level up to 1800 m (Francis 2014; Bugwood Wiki, 2015). It tolerates a wide range of soil types but is limited to temperate and continental climates (USDA-NRCS, 2015).

The species is commonly found in disturbed areas such as along railway lines, roadsides and fence lines (DiTomaso et al., 2013). It is also often found in sites following fire as it is well adapted to colonize recently burnt sites (USA Forestry Service, 2015). It is abundant in riparian zones, edges of wetlands and other areas that experience occasional flooding such as irrigation channels.

Habitat List

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CategoryHabitatPresenceStatus
Littoral
Coastal areas Present, no further details Harmful (pest or invasive)
Terrestrial-managed
Cultivated / agricultural land Present, no further details Harmful (pest or invasive)
Disturbed areas Principal habitat Harmful (pest or invasive)
Managed grasslands (grazing systems) Present, no further details Harmful (pest or invasive)
Rail / roadsides Principal habitat Harmful (pest or invasive)
Terrestrial-natural/semi-natural
Natural forests Present, no further details Harmful (pest or invasive)
Riverbanks Principal habitat Harmful (pest or invasive)

Biology and Ecology

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Genetics

The chromosome number for R. armeniacus was reported as 2n = 28 (Thompson, 1995).

Reproductive Biology

R. armeniacus reproduces both vegetatively and by the production of seed. Vegetative reproduction is the dominant form and occurs in several ways. The canes can root at the tips and form daughter plants when touching the ground. Roots can sprout at the tips and both root and cane cuttings can establish new plants. It has been reported that a single cane cutting can form a thicket of 5 m in diameter in less than two years (Soll, 2004).

Thickets have been reported to produce between 7,000-13,000 seeds /m2. Seeds remain viable for several years and germination has been reported as slow (Cal-IPC, 2015). The seed coat is impermeable and the embryo remains dormant until it breaks (Ensley, 2015). Ingestion by birds or mammals and long warm periods followed by long cold periods aid germination. It has been reported that seed germination requires more than about 50% of full sunlight (Cal-IPC, 2015). As a result seed viability and seedling recruitment is limited by shading present in mature thickets (Soll, 2004).

Physiology and Phenology

R. armeniacus is predominantly evergreen but does die back with colder temperatures. Seeds germinate in spring and once seedlings are established much of the subsequent reproduction is vegetative. Growth and spread of the species has been reported to be rapid (Caplan and Yeakley, 2006). During spring there are usually four live canes originating from an individual root crown. Two of the canes are primary and two are one year old. The canes do not flower in their first year and grow between 2-10 m in length. Flowering occurs in their second or even third years (Francis, 2014). Flowering begins in spring and fruits ripen in midsummer. In the winter the fruiting canes senesce while the first year canes produce branches and will set fruit the following year (Jones, 2004).

Population Size and Structure

This species tends to form dense thickets that exclude other vegetation, thus forming near monocultures. The thickets can reach densities of up to 525 stems (canes) /m2 and the individual canes can reach 6-12 m horizontally and 3 m vertically.

Associations

In California R. armeniacus has been reported to be a host for the bacteria Xylella fastidiosa which causes Pierce’s disease in grapes (Caplan and Yeakley, 2006). It is also a host to the leafhopper Homalodisca vitripennis, which carries the bacteria and facilitates the spread of the disease (Calflora, 2015).

Environmental Requirements

R. armeniacus is found in temperate environments, from coastal estuaries to inland upland sites as high as 1,800 m above sea level (Stannard, 2014). The species has been reported to tolerate temperatures as low as -18°C and as high as 37°C. It tolerates a wide range of soil types, growing in fine, medium and coarse textured soils that are acid to alkaline. The species tolerates occasional flooding with both fresh and brackish water. The mean annual rainfall for its distribution is 760 mm, however, in drier climates it is confined to riparian zones or alongside artificial waterways (Francis, 2014). A field study of the species adaptive capacity to drought demonstrated that it is capable of both rapid water use when water is widely available and effective at water acquisition when it is in short supply (Yeakley and Caplan, 2008). R. armeniacus prefers full sunlight but also grows well under light canopies. It does not, however, grow well under dense canopies (Washington State Noxious Weed Control Board, 2015).

Climate

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ClimateStatusDescriptionRemark
BS - Steppe climate Tolerated > 430mm and < 860mm annual precipitation
BW - Desert climate Tolerated < 430mm annual precipitation
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Tolerated Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
31-47

Air Temperature

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Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -18
Mean annual temperature (ºC) 5 20
Mean maximum temperature of hottest month (ºC) 21 32
Mean minimum temperature of coldest month (ºC) -4 7

Rainfall

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ParameterLower limitUpper limitDescription
Mean annual rainfall760mm; lower/upper limits

Rainfall Regime

Top of page Uniform
Winter

Soil Tolerances

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Soil drainage

  • free
  • impeded
  • seasonally waterlogged

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • infertile
  • saline
  • shallow

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Phragmidium violaceum Pathogen Leaves to genus Chile, Australia, New Zealand Rubus species

Notes on Natural Enemies

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In 2005 a rust fungus, Phragmidium violaceum, infecting R. armeniacus was reported in Oregon, USA. This was the first report of the fungus in the USA and has since been recorded in British Columbia, Canada (Callan et al., 2011). The rust is native to wild blackberries in Africa, the Middle East and Europe. The disease causes leaf-spots and blights on leaves of R. armeniacus. Heavily infected leaves become defoliated. This pathogen and also affects buds, unripe fruit and growing parts of the cane (Peters, 2012). 

Means of Movement and Dispersal

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Natural Dispersal

R. armeniacus is often found along waterways suggesting that natural dispersal of the seeds along waterways is common. Seed dispersal is also assisted by gravity. Vegetative reproduction, where the canes take root via the tips has been reported to result in dispersal distances of up to 3 m from the parent plant (Ensley, 2015).

Vector Transmission

Animals and birds eat the fruit and seed, thereby contributing to both long and short distance dispersal, depending on the animals’ range. A study across 91 islands in the Gulf Islands of British Columbia, Canada and the San Juan Islands of Washington state, USA, confirmed that birds play a key role in spreading R. armeniacus (Bennett et al., 2011).

Accidental Introduction

Given that new plants can establish from cane and root cuttings, it is likely that accidental dispersal occurs when plant material is cut and carried and accidentally deposited on new sites.

Intentional Introduction

Like many Rubus species, R. armeniacus has been intentionally introduced into a number of countries for its production of fruit.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Escape from confinement or garden escapeCommon garden escape Yes Ceska, 1999
HorticultureFirst introductions were for horticultural purposes Yes Ceska, 1999

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Plants or parts of plantsRoot and cane cuttings can establish new plants Yes Soll, 2004
WaterSeeds Yes Ensley, 2015

Impact Summary

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CategoryImpact
Cultural/amenity Negative
Economic/livelihood Positive and negative
Environment (generally) Positive and negative

Economic Impact

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The removal of R. armeniacus in areas where it is invasive and poses an ecological threat results in significant economic costs. For example it has been referred to as the most widespread and economically disruptive noxious weed in western Oregon, USA (Oregon Department of Agriculture, 2015). There is a lack of quantitative analysis on what these costs amount to but estimates for North America are in the order of millions of dollars (Peters, 2012).

The species has been known to interfere with agriculture and forestry activities and has been reported to be a vector of the bacterial pathogen, Xylella fastidiosa, which causes Pierce’s disease in grapevines (Ensley, 2015).

Environmental Impact

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The specie can outcompete many native North American species and degrades natural ecosystems. It has the tendency to form dense thickets making it difficult for shade intolerant species to survive. For example in the USA, Douglas fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa) and Oregon white oak (Quercus garryana), are particularly susceptible to competition from R. armeniacus (Soll, 2004). A study from Oregon suggests that without control of R. armeniacus and other invasive species present in riparian ecosystems, the overall biodiversity of these areas could be adversely affected (Fierke and Kauffman, 2006). The dense thickets can limit movement of large animals, for example, stopping them from reaching water and foraging areas (Soll, 2004).

On the other hand, when established, R. armeniacus thickets provide habitats and a source of food for many birds and both small and large mammals. Honey bees have also been reported to frequently visit the flowering species. It has however been noted that thickets of R. armeniacus are not a good substitute for diverse vegetation such as in native forests and in riparian zones (Soll, 2004).

Social Impact

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The fruits are commonly collected by berry pickers in both Europe and the USA. In the Pacific Northwest of the USA, this species is an important part of rural culture with many business names referring to the blackberry (Stannard, 2014). In the USA and Canada, the species has also been reported to host the rust causing fungus Phragmidium violaceum, which has caused severe economic loss to commercially grown blackberries during the 2005 season in Oregon (Johnson and Mahaffee, 2010).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Is a habitat generalist
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Highly mobile locally
  • Fast growing
  • Has high reproductive potential
  • Gregarious
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
  • Has high genetic variability
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Negatively impacts agriculture
  • Negatively impacts forestry
  • Negatively impacts animal health
  • Reduced native biodiversity
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - shading
  • Competition
  • Hybridization
  • Rapid growth
  • Produces spines, thorns or burrs
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately

Uses

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Economic Value

R. armeniacus is valued for its large fruit and is cultivated in Europe for both domestic and commercial fruit production. The wild fruits are often harvested and are suitable for canning, freezing or eating fresh (Stannard, 2014).

Environmental Services

R. armeniacus has been cultivated along fences and trellises to create impenetrable barriers (Francis, 2014). Beneficial associations with native bees, bumble bees (Bombus species) and hummingbirds (Trochilidae family) for the pollen and nectar were reported in California (Calflora, 2015). The fruits from R. armeniacus provide food for many birds and small mammals such as the coyote (Canis latrans), red foxes (Vulpes vulpes) squirrels (Sciuridae family) and black bears (Ursus americanus). A number of animals also rely on the thickets for shelter. In North America, especially during the winter months, deer (Cervidae family), elk (Cervus canadensis), rabbits (Leporidae family), porcupines (Erethizontidae species), beavers (Castor species) and mountain beavers (Aplodontia rufa) have been reported to consume leaves, buds, twigs and the cambium (Klein, 2011; Francis, 2014).

Uses List

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Environmental

  • Boundary, barrier or support

Human food and beverage

  • Fruits

Similarities to Other Species/Conditions

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As the taxonomic confusion suggests R. armeniacus is easily confused with other species. It can be difficult to distinguish between species in the R. fruticosus aggregate, of which R. armeniacus belongs. R. laciniatus (cutleaf blackberry) is also a closely related species.

Prevention and Control

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Control

Cultural Control and Sanitary Measures

R. armeniacus tends to invade disturbed sites such that protecting native species and the dense planting of shade producing shrubs or trees can provide control (Soll, 2004; Bugwood wiki, 2015).

Physical/Mechanical Control

A range of physical control methods focused on mechanical removal of both the vegetation and roots are available. These include hand pulling, hand hoeing, cutting, burning, goat grazing, digging and removal with machines such as disking or ploughing. Each method has reported advantages and disadvantages and several methods are often used in combination. For example, hand pulling is most suitable when the plants are in seedling stage. Cutting and burning both effectively remove the above ground part of the plant but must be repeated multiple times over a number of years because the root crown will continue to re-sprout. Burning does not prevent re-sprouting from the root crowns either and has been reported to provide good conditions for seedling germination (Ensley, 2015). However, in wetlands, cutting to ground level has proven effective as without the supporting canes, roots are reportedly unable to survive in anaerobic conditions (Soll, 2004). Similarly disking or ploughing should be repeated and care taken that the rhizomes are not spread further. Digging is labour intensive, but when thoroughly undertaken, i.e. removing all large root fragments, is an effective method for removal and is a suitable follow up to cutting (Soll, 2004; Stannard, 2014). A recent study from the Pacific Northwest of the USA, compared the effectiveness of high intensity, short duration goat grazing with mowing and goat grazing followed by mowing. Each treatment caused the species to decline but there was not a significant difference between the three treatments (Ingham, 2014).

Biological Control

The rust fungus, Phragmidium violaceum, recently discovered on R. armeniacus in North America has triggered research into its potential as a biological control agent. Specific strains of the rust have been used to control other invasive Rubus species in Chile, Australia and New Zealand (Peters, 2012).

Chemical Control

Both selective and non-selective herbicides are used for control of R. armeniacus. Foliar applied herbicides have been reported most effective when the plants are in full leaf and this can be enhanced when the plants are water stressed (Soll, 2004). Although timing of application tends to vary between herbicides. The most commonly used herbicides include glyphosate, dicamba, dicamba/2,4-D combinations and triclopyr, metsulfuron and picloram (Soll, 2004; DiTomaso, 2010). In many cases more than one application may be needed. Triclopyr can also be applied to the basal regions of the plants, to the dormant stems and to freshly cut root crowns or stems. The latter is often recommended as a follow up strategy following manual removal. The advantage of these treatments is that they can be applied outside of the berry picking season (DiTomaso, 2010).

Ecosystem Restoration

When undertaking physical or chemical control methods of R. armeniacus, it is imperative to plant desirable native plant species on the site to help reduce re-invasion by R. armeniacus (Stannard, 2014).

References

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Contributors

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26/05/2015 Original text by:

Madeleine Florin, Consultant, The Netherlands

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