Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Hitchhiker (pathway cause)



Hitchhiker (pathway cause)


  • Last modified
  • 12 June 2017
  • Datasheet Type(s)
  • Pathway Cause
  • Preferred Scientific Name
  • Hitchhiker (pathway cause)
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Preferred Scientific Name

  • Hitchhiker (pathway cause)

Species Transported by Cause

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SpeciesNotesLong DistanceLocalReferences
Acacia glauca (wild dividivi)Mud containing seeds can attach to vehicles or animals Yes
Acanthophora spiciferaPacific Western Central to Hawaii Yes Doty, 1961
Acanthospermum australe (spiny-bur) Yes Yes
Acarapis woodi (honeybee mite)Movement of infected bees by beekeepers and commercial suppliers Yes Yes Korpela, 1998; Woodward and Quinn, 2011
Achatina fulica (giant African land snail) Yes Yes
Achillea millefolium (yarrow) Yes Yes Barros and Pickering, 2014
Adoretus sinicus (Chinese rose beetle)In ornamental plant trade Yes McQuate and Jameson, 2011b
Aedes albopictus (Asian tiger mosquito) Yes Yes
Aethina tumidaOn apiculture products or equipment Yes Yes OIE, 2012
Ageratina riparia (mistflower) Yes
Ageratum houstonianum (Blue billygoatweed)Can attach to animals, vehicles, clothes. Yes Yes Johnson, 1971
Agrostis avenacea (Pacific bent grass)On land transport, but particularly via railway. Yes Yes Victorian Resources Online, 2015
Akebia quinata (five-leaf akebia)Intentional introduction Yes Schweingruber et al., 2011; USDA-ARS, 2013
Alexandrium minutumcysts in ballast water, possible but not documented Yes Yes
Amaranthus tuberculatus (rough-fruited water-hemp)Can adhere to farm machinery Yes Costea et al., 2005
Amphibalanus improvisus (bay barnacle)On vessels, worldwide Yes Yes Carlton et al., 2011
Amphisbaena fuliginosa (speckled worm lizard)Possible pathway Yes Murphy et al., 2010
Andropogon virginicus (broomsedge) Yes Yes
Anolis aeneus (bronze anole)Migrants' belongings Yes Hailey et al., 2009
Anolis cristatellus (Puerto Rican crested anole) Yes Fitch et al., 1989
Anolis extremus (Barbados anole)Likely for St Lucia and Venezuela introductions Yes Gorman, 1976; Rivas et al., 2012
Anolis trinitatis (St Vincent bush anole)Migrants' belongings Yes Hailey et al., 2009
Anolis wattsi (Watts' anole)Likely for St Lucia introduction, and jump dispersal within Trinidad Yes Yes Gorman, 1976; White and Hailey, 2006
Anoplolepis gracilipes (yellow crazy ant) Yes Yes
Anthoxanthum odoratum (sweet vernal grass)Probably in hay and straw Yes Yes
Aphanomyces astaci Yes Yes Oidtmann et al., 2002
Aproceros leucopoda (elm zigzag sawfly)Associations between spread and roads are known Yes Yes Doty, 1961
Arctotheca calendula (capeweed) Yes
Arcuatula senhousia (Asian date mussel) Yes NIMPIS, 2002
Argemone ochroleuca (pale Mexican pricklypoppy) Yes BioNet-EAFRINET, 2011
Aristolochia elegans (elegant Dutchman’s pipe) Yes Randall, 2012; Starr et al., 2003
Arrhenatherum elatius (false oat-grass)Can attach to animal fur for limited dispersal Yes Couvreur et al., 2005
Arthraxon hispidus (small carpetgrass) Yes Yes
Ascidiella aspersa (European sea squirt) Yes Yes
Asterias amurensis (northern Pacific seastar) Yes Yes
Atriplex semibaccata (Australian saltbush) Yes Yes
Aulacaspis yasumatsui (cycad aulacaspis scale) Yes Yes
Austropuccinia psidii (myrtle rust)Accidental as contaminant on timber, packaging and containers; on personal effects and movement from Yes Yes Carnegie and Cooper, 2011; Grgurinovic et al., 2006
Bactrocera cucurbitae (melon fly)Seychelles Yes Yes
Bactrocera dorsalis (Oriental fruit fly) Yes Yes
Bactrocera musae (banana fruit fly)Possibly introduced to Lihir Island (New Ireland) and Manus Island in infested fruit brought from mainland Papua New Guinea, low population levels Yes Doty, 1961
Bactrocera tryoni (Queensland fruit fly)>2 YR (local), ~10 YR (long distance) Yes Yes Baker and Cowley, 1991; Dominiak and Barchia, 2005; Maelzer et al., 2004
Bactrocera zonata (peach fruit fly) Yes Yes
Bassia hyssopifolia (fivehook bassia) Yes Yes
Batrachochytrium salamandrivorans (Bsal)Possible human-mediated (direct) dispersal by pathogen adherence to boots or shoes Yes Doty, 1961
Bidens frondosa (beggarticks) Yes Doty, 1961
Blattella germanica (German cockroach) Yes Yes Rockman, 1992
Boa imperator (Central American Boa)Accidental as stowaway in cargo Yes Doty, 1961
Boerhavia coccinea (scarlet spiderling)sticky seeds Yes Yes Jurado et al., 1991
Bothriocephalus acheilognathiMoved worldwide in host fish, especially carp for aquaculture Yes Yes Bauer and Hoffman, 1976; Choudhury and Cole, 2012; Scholz et al., 2012
Bothriochloa ischaemum (yellow bluestem) Yes Hilty, 2014
Bothriochloa pertusa (pitted beard grass)Livestock, birds and humans Yes
Botrylloides violaceus (violet tunicate) Yes Yes Carlton and Geller, 1993; Dijkstra et al., 2007
Brachypodium distachyon (purple false brome)Florets can be dispersed by vehicle tires and human activities, particularly in contaminated hay Yes Doty, 1961
Brachypodium sylvaticum (slender false brome) Yes Yes Heinken and Raudnitschka, 2002
Brassica nigra (black mustard)accidental Yes Yes Doty, 1961
Brassica tournefortii (African mustard)Wet seeds form a sticky gel like coating so can adhere to passing animals or vehicles Yes Yes Minnich and Sanders, 2000
Bromus secalinus (rye brome)Seeds attach to humans and animals Yes Hilty, 2015
Bunias orientalis (Turkish warty-cabbage) Yes
Bythotrephes longimanus (spiny waterflea)Long-distance via transatlantic ship transportation in ballast water; Local via the attachment onto Yes Yes Branstrator et al., 2006; Lui et al., 2010
Cabomba caroliniana (Carolina fanwort) Yes Yes Les and Mehrhoff, 1999
Cactoblastis cactorum (cactus moth) Yes Yes
Cameraria ohridella (horsechestnut leafminer) Yes Yes Gilbert et al., 2004; Gilbert et al., 2005
Candidula intersecta (wrinkled dune snail)Terracotta tiles from Spain and South America into USA containers especially via Caribbean transship Yes Yes Meissner et al., 2009
Caprella muticaFound attached to commercial and recreational boat hulls Yes Yes Ashton, 2006
Carcinus maenas (European shore crab) Yes Yes Cohen and Carlton, 1995
Carduus pycnocephalus (Italian thistle) Yes Yes
Celtodoryx ciocalyptoidesAccidentally from the North West Pacific on Pacific oysters Yes Pérez et al., 2006; Henkel and Janussen, 2011
Cenchrus ciliaris (Buffel grass) Yes Yes
Centaurea solstitialis (yellow starthistle) Yes
Ceratocephala testiculata (bur buttercup) Yes Yes
Ceratocystis platani (canker stain of plane) Yes Yes
Ceratophyllum demersum (coontail) Yes Yes
Channa argus argus (northern snakehead) Yes Yes Courtenay and Williams, 2004
Christella dentata (soft fern)Spores and gametophytes could be easily transported Yes
Citrus leprosis virus C (leprosis of citrus)The infected mite vector can be transported in many ways (fruit, vegetables, host plants, clothes, e Yes Yes
Clerodendrum indicum (Turk's turban)Seeds and root fragments possibly transported by soil stuck to hooves, shoes, on wheels, etc. Yes
Coccinia grandis (scarlet-fruited ivy gourd)Seeds can be spread by birds, rodents and possibly pigs. Yes Englberger, 2009
Cochliomyia hominivorax (New World screwworm)Very low risk Yes Yes
Codium fragile subsp. tomentosoidesBetween European countries, NW Atalantic coast, and Southern Hemisphere Yes Yes Bouck and Morgan, 1957; Carlton and Scanlon, 1985; Dromgoole, 1975; Silva, 1955; Silva, 1957; Silva, 1979
Codium parvulumVia ballast water or hull fouling Yes Hoffman et al., 2014
Corella eumyota (orange-tipped sea squirt)Hull fouling, floating debris, contaminated mussels or oysters Yes Yes Doty, 1961; El-Nagar et al., 2010
Corvus splendens (house crow)On board ships particularly from Mumbai, Colombo, Aden Yes Ryall, 1994; Ryall, 2002
Corythucha ciliata (sycamore lace bug)Accidental - on vehicles Yes Yes
Cosmos caudatus (wild cosmos)Small seed contaminant Yes Yes
Cosmos sulphureus (sulphur cosmos)Seeds are adapted for external attachment and animal dispersal Yes Jansen, 2005; PlantPono, 2014
Crassostrea virginica (eastern oyster) Yes Yes
Crassula helmsii (Australian swamp stonecrop) Yes Yes Environment Agency, 2003
Crypsis schoenoides (swamp pricklegrass)Accidental dispersal via waterfowl movements Yes Green et al., 2002
Ctenosaura similis (black spiny-tailed iguana)Presumably brought to Venezuela accidentally on cargo ships. Also spread in Florida via vehicles Yes Yes Barrio-Amorós and Rivas-Fuenmayor, 2008; Krysko et al., 2003
Culex quinquefasciatus (southern house mosquito)Larvae in bilge water or cargo. Adults in cargo or aeroplane cabins. Yes Bataille et al., 2009; Joyce, 1961; Lounibos, 2002; Smith and Carter, 1984
Cuphea carthagenensis (Colombian waxweed) Yes Technigro, 2011
Cynara cardunculus (cardoon)Seeds attach to passing animals or vehicles Yes Yes Kelly, 2000
Cynoglossum amabile (Chinese forget-me-not) Yes Melcher et al., 2000
Cyperus papyrus (papyrus) Yes Yes
Daphnia lumholtziResting eggs enclosed in a protective ephippium which possess hooks that allow attachment Yes Yes Benzie, 1988; Dzialowski et al., 2000; Fryer, 1996; Havel and Hebert, 1993; Havel and Shurin, 2004
Datura innoxia (downy thorn apple) Yes
Datura metel (Hindu datura) Yes Yes PIER, 2014
Deparia petersenii subsp. petersenii (Petersen’s lady fern)Spore contaminated equipment and vehicles could be involved in transport. Yes
Deroceras laeve (meadow slug)Accidental Yes AnimalBase, 2015
Descurainia sophia (flixweed) Yes Howard, 2003
Desmodium incanum (creeping beggerweed)Stick-tight seeds provide adherence Yes Yes Mori and Brown, 1998
Didemnum vexillum Yes Yes Carlton and Geller, 1993; Dijkstra et al., 2007a
Digitaria bicornis (Asian crabgrass)Might be carried unintentionally in clothes, shoes, etc., due to small size of seeds. Also carried in animal fur Yes Doty, 1961
Digitaria fuscescens (yellow crab grass)Might be carried unintentionally in clothes, shoes, etc Yes
Diplosoma listerianum Yes Yes Carlton and Geller, 1993; Dijkstra et al., 2007a
Discus rotundatus (rotund disc)Not explicitly mentioned in literature, but likely based on the species’ biology Yes
Dreissena polymorpha (zebra mussel) Yes Yes
Drosophila suzukii (spotted wing drosophila) Yes
Ehrharta calycina (perennial veldtgrass)agricultural machinery Yes Bossard et al., 2000
Elephantopus mollis (elephant's foot)On clothing, animals or machinery Yes Queensland Government, 2014
Eleutherodactylus coqui (Caribbean tree frog) Yes Yes
Eleutherodactylus planirostris (greenhouse frog)Thought to have been introduced to Mexico and Jamaica via the shipping and cargo trade Yes Yes Doty, 1961; Jensen et al., 2008; Doty, 1961; Reynolds, 2012; Schwartz, 1974; Stewart, 1977; Zippel et al., 2005
Elodea canadensis (Canadian pondweed) Yes Yes
Epilobium ciliatum (northern willowherb) Yes Yes
Epiphyas postvittana (light brown apple moth) Yes
Eragrostis lehmanniana (Lehmann lovegrass)seed spread in hay, cattle and vehicles Yes Yes USDA Forest Service, 2014
Eragrostis plana (South African lovegrass)Seeds moved in cattle, dogs fur and paws and adhered to vehicles and machinery Yes Yes Doty, 1961
Erechtites glomerata (fireweed) Yes
Erigeron karvinskianus (Karwinsky’s fleabane)In India, probably first introduced along with seeds of ornamental plants from Australia Yes Rao and Sagar, 2012
Erionota thrax (banana skipper) Yes Yes
Erionota torus (banana skipper)Motor vehicles, boats and aircraft could all carry hitchhiker adults of E. torus. Yes Yes Cock, 2015
Erodium botrys (long-beaked stork's bill)In animal products (wool) Yes Yes Alien plants of Belgium, 2013
Erodium cicutarium (common storksbill) Yes Yes
Euphorbia terracina (false caper) Yes
Euschistus heros (Neotropical brown stink bug)Found in crop residues. Yes Yes Saluso et al., 2011
Ferrisia virgata (striped mealybug)Accidental introduction on plants, and also on machinery, tools and workers Yes Yes
Festuca pratensis (meadow fescue) Yes
Ficopomatus enigmaticus (tubeworm)One specimen was collected in an oyster clump in the Port of Brunswick in East River Yes Yes USGS, 2009
Forficula auricularia (European earwig)Most important pathway for this species; nymphs and adults Yes Yes Crumb et al., 1941
Fragaria vesca (wild strawberry)Seeds dispersed by animals Yes Schulze et al., 2012; Willson, 1993
Frankliniella occidentalis (western flower thrips)Inadvertently transported in infested plant material. Yes Yes Nickle, 2003; Vierbergen, 1995
Galega officinalis (goatsrue) Yes
Glyceria declinata (small sweet grass) Yes Yes
Gracilaria salicorniaPacific Western Central to Hawaiian Islands Yes Smith et al., 2004
Grateloupia turuturu Yes Farnham, 1978; Farnham, 1980; Marston and Villalard-Bohnsack, 2002; Simon et al., 2001
Gymnodinium catenatumJapan to Australia Yes Yes Bolch and Salas, 2007
Halogeton glomeratus (halogeton) Yes
Halyomorpha halys (brown marmorated stink bug)Frequently occurs due to H. halys seeking sheltered overwintering sites. Yes Yes Hoebeke and Carter, 2003
Haplaxius crudus (American palm cixiid) Yes Yes
Harmonia axyridis (harlequin ladybird) Yes Yes Brown et al., 2008b
Hemidactylus frenatus (common house gecko)Accidental introduction. See all citations under History of Introduction/Spread Yes Yes
Hemigrapsus sanguineus (Asian shore crab) Yes
Hemigrapsus takanoi (brush-clawed shore crab)Accidental introduction Yes Gollasch, 1999
Heracleum sosnowskyi (Sosnowskyi's hogweed)Seeds can get attached to cloth, footwear, animal fur or to vehicles Yes Yes Kabuce, 2006
Herpestes auropunctatus (small Indian mongoose) Yes
Heterotheca grandiflora (telegraph weed)Probably an accidental introduction to Hawaii, Australia, Japan, and possibly Arizona and Utah Yes PIER, 2015
Hirschfeldia incana (shortpod mustard) Yes Brooks, 2004
Hydrocharis morsus-ranae Yes Yes USGS-NAS, 2002
Hygrophila polysperma (Indian swampweed) Yes Kay and Hoyle, 2001
Hypnea musciformisBetween Hawaiian Islands Yes Russell and Balazs, 1994
Hyptis suaveolens (pignut) Yes Doty, 1961
Icerya samaraia (steatococcus scale) Yes Yes Miller et al., 2014a; Miller et al., 2014b
Impatiens parviflora (small balsam)On the fur of wild animals Yes Trepl, 1984
Indigofera spicata (creeping indigo)Seeds dispersed by human and animal movement, e.g. horses Yes Yes Morton, 1989
Inula britannica (british yellowhead) Yes
Jatropha gossypiifolia (bellyache bush) Yes
Juncus effusus (common rush) Yes
Juncus ensifolius (swordleaf rush)Accidental contaminant in seeds/peat/soil, with other aquatic plants, or on people or vehicles Yes Dörr, 1995; Pohjakallio and Hämet-Ahti, 1974; Poland, 2005
Juncus tenuis (slender rush) Yes Yes Richards, 1943
Lactuca floridana (woodland lettuce) Yes Yes
Lagarosiphon major (African elodea) Yes USDA-ARS, 1997
Lemna perpusilla (duckweed) Yes Yes Maki and Galatowitsch, 2004
Lepidium perfoliatum (clasping pepperweed)Potential seed contaminant. Has been accidentally spread with bird feed and as contaminant in grain Yes Yes NDFF, 2016; USDA-ARS, 2016
Lepidium virginicum (Virginian peppercress)As contaminant in hay, grains and wool. Yes Yes Doty, 1961
Leptocybe invasa (blue gum chalcid)Small L. invasa adults or movement of leaves with galls (e.g. leaves stuck outside the windscreen of a vehicle) Yes
Leucanthemum vulgare (oxeye daisy) Yes
Leucaspius delineatus (sunbleak) Yes
Liberibacter africanus (African greening) Yes
Limnobium laevigatum (South American spongeplant)Propagules are dispersed as hitchhikers on watercrafts. Yes Akers, 2010
Limnoria lignorum (gribble) Yes Yes
Littorina littorea (common periwinkle)With Atlantic seaweeds used as packing for long distance transport of bait worms and shellfish/fish Yes Carlton, 2007
Ludwigia grandiflora (water primrose) Yes Ruaux et al., 2009
Ludwigia peploides (water primrose) Yes Ruaux et al., 2009
Lumbricus rubellus Yes Yes Gates, 1972; Gates, 1982
Lumbricus terrestris Yes Yes Gates, 1972; Gates, 1982
Lygodium japonicum (Japanese climbing fern)Spores spread when pine straw collected from infested sites and used as mulch elsewhere Yes Doty, 1961
Lythrum maritimum (pukamole)Seeds can be transported on vehicles or clothing Yes Yes Anderson et al., 1992
Mainsia rubi Yes
Marrubium vulgare (horehound) Yes
Medicago polymorpha (bur clover)Probably as a contaminant in hay, straw and agricultural seed Yes Yes
Megaplatypus mutatus Yes Yes
Melilotus officinalis (yellow sweet clover)e.g. vehicles, machinery, grain, soil Yes Yes Doty, 1961
Melissococcus plutoniusOn apiculture products or equipment Yes Doty, 1961
Mesosphaerum pectinatum (comb bushmint)Accidental, frequent Yes Yes
Microlaena stipoides (meadow rice grass, meadow ricegrass)On animal coats e.g. dogs, wild pigs in Hawaii Yes Medeiros et al., 1998; Doty, 1961
Microstegium vimineum (Nepalese browntop)Moderate uncertainty Yes Baiser et al., 2008; Warren et al., 2010
Mikania micrantha (bitter vine) Yes Yes
Moneilema semipunctatum (cactus borer beetle)May be present as adults of larvae in plants collect from the wild Yes Yes Woodruff, 2010
Mononychellus tanajoa (cassava green mite)Accidental introduction, common pathway Yes Yes
Moraea (Cape tulip) Yes
Moraea collina (Cape tulip) Yes
Moraea miniata (two-leaf Cape-tulip) Yes
Mycale grandis (orange keyhole sponge) Yes Yes
Myriophyllum heterophyllum (broadleaf watermilfoil)May attach to boats and boat trailers Yes
Mytilicola intestinalis (mussel red worm)In infected bivalve hosts attached to ship/boat hull. Yes Yes Rohde, 1993
Myxobolus cerebralis (whirling disease agent)Potential movement on anglers' gear Yes Gates et al., 2008
Nasturtium microphyllum (one-row watercress) Yes
Neolecanium cornuparvum (magnolia scale)Can be carried on the feet of birds and by ants Yes Herms and Nielsen, 2004; Vanek and Potter, 2010b
Neyraudia reynaudiana (burma reed) Yes Yes Hill, 1976
Nicotiana plumbaginifolia (Tex-Mex tobacco)Might be dispersed unintentionally due to small seed size Yes Yes
Onopordum illyricum (Illyrian thistle) Yes Yes
Oplismenus hirtellus subsp. undulatifolius (wavyleaf basketgrass) Yes Yes
Orobanche cernua (nodding broomrape) Yes
Orobanche cumana (sunflower broomrape) Yes
Osteopilus septentrionalis (Cuban treefrog)Accidentally transported in crates of vegetables Yes Yes
Paederia foetida (skunkvine) Yes Yes Pemberton and Pratt, 2002
Paenibacillus larvaeOn apiculture products or equipment Yes Yes Antúnez et al., 2010
Palaemon elegans (rock shrimp) Yes
Palaemon macrodactylus (oriental shrimp)Probably occurs but not observed Yes Lavesque et al., 2010
Parentucellia viscosa (yellow glandweed) Yes Yes
Parthenium hysterophorus (parthenium weed)Animals, vehicles, machinery, grains, humans Yes Yes PAG, 2000; Doty, 1961
Paspalum dilatatum (dallisgrass)unintentionally dispersed by animals and humans Yes Yes Eurobodalla Shire Council, 2017; PIER, 2017
Pastinaca sativa (parsnip)Attachment to machinery involved with farming, landscaping and construction activities Yes Yes Cain et al., 2010
Pennisetum setaceum (fountain grass)Seeds stick to clothing, fur Yes Yes Halvorson and Guertin, 2003
Petricolaria pholadiformis (false angel wing) Yes Yes Rosenthal, 1980
Philornis downsi Yes
Phytophthora alni species complex (alder Phytophthora)Movement of infected soil on shoes/machinery (not specifically demonstrated for the alder Phytophthora but known to be important for root phytophthoras) or livestock Yes Webber and Rose, 2008; Doty, 1961
Phytophthora cinnamomi (Phytophthora dieback)Probably very common Yes Yes
Pinctada imbricata radiata (rayed pearl oyster) Yes Oliverio et al., 1992
Pistia stratiotes (water lettuce) Yes Yes Rivers, 2002
Plasmodiophora brassicae (club root)Infested soil can be moved on footwear Yes Wallenhammar et al., 2016
Pluchea carolinensis (sourbush)Accidentally introduced as a result of military activity Yes Yes PIER, 2015
Plutella xylostella (diamondback moth) Yes Yes
Podarcis sicula (Italian wall lizard)One of the main causes in Europe and frequent as there is no surveillance programme Yes Carretero and Silva-Rocha, 2015; Mizsei et al., 2016; Tok et al., 2015
Polypogon monspeliensis (annual beard grass)As contaminant in hay, straw or packing material Yes Yes
Pomacea canaliculata (golden apple snail) Yes Yes
Pomacea maculataSnails eggs could be transported on the outside of boats Yes EFSA Panel on Plant Health, 2012
Pontogammarus robustoidesIn ship fouling Yes Yes Arbaciauskas, 2005; Kurashov et al., 2012a
Potamogeton crispus (curlyleaf pondweed) Yes Yes ISSG, 2006
Prunella vulgaris (self-heal) Yes
Pseudochattonella verruculosa Yes
Pseudococcus viburni (obscure mealybug)On farm machinery used in infested vineyards or orchards Yes Yes
Pseudogymnoascus destructans (white-nose syndrome fungus)May be spread by infected bats, & contact with contaminated substrates and human clothing/equipment Yes Yes Ballmann et al., 2017; Carpenter et al., 2016; Lorch et al., 2011; Lorch et al., 2013b; Mulec et al., 2013; Shelley et al., 2013; Sleeman, 2011; Wilder et al., 2015
Pterolepis glomerata (false meadowbeauty)Propagules dispersed unintentionally - grows in heavily trafficked areas Yes PIER, 2015
Pyrrhalta luteola (elm leaf beetle) Yes Yes
Raffaelea lauricola (laurel wilt) Yes Yes Fraedrich et al., 2008
Raffaelea quercivora (Japanese oak wilt)Predicted but not confirmed Yes Yes
Rattus norvegicus (brown rat)Historically introduced by boat. Still locally introduced by boat today Yes Yes Russell et al., 2008
Rhagoletis cingulata (cherry fruit fly)Infested fruits, pupae in transportation units Yes Yes
Rhithropanopeus harrisiiOn ships from North America to Europe; Panama and Japan Yes Christiansen, 1969; Iseda et al., 2007; Roche et al., 2009
Rottboellia cochinchinensis (itch grass)Railcars from Mexico to USA Yes Lehtonen, 2003
Sacciolepis indica (glen woodgrass)Multiple inferences Yes Hitchcock, 1971; Mallett and Orchard, 2002; Proctor, 1982
Salsola kali (common saltwort) Yes Yes
Salsola paulsenii (barbwire Russian thistle) Yes Yes
Salvinia auriculata (giant salvinia) Yes ISSG, 2009
Salvinia minima Yes Yes USGS, 2005
Salvinia molesta (kariba weed) Yes McFarland et al., 2004
Sargassum muticum (wire weed) Yes Yes
Schizoporella japonica (orange ripple bryozoan)On oysters Yes Doty, 1961
Sclerophthora rayssiae var. zeae (brown stripe downy mildew of maize)Accidental, potentially on farm equipment Yes Yes
Securigera varia (crown vetch)Seeds mixed with cereals, wool and building materials Yes Yes Doty, 1961
Senna alata (candle bush)Reported as likely to be dispersed unintentionally Yes PIER, 2016
Senna occidentalis (coffee senna)As contaminants in agricultural produce such as hay and grain Yes Yes Parsons and Cuthbertson, 1992
Senna septemtrionalis (smooth senna)Mud stuck to bottom of shoes, machinery, or animals Yes Yes Weeds of Australia, 2014
Setaria parviflora (knotroot foxtail)Possibly wool or sheep Yes Ryves et al., 1996
Sida acuta (sida) Yes Lonsdale et al., 1995
Siganus rivulatus (marbled spinefoot)In ballast water Yes Wonham et al., 2000
Silene latifolia subsp. alba (white campion)Originally introduced in ship ballast Yes
Solanum erianthum (potato tree) Yes Roe, 1979
Solanum rostratum (prickly nightshade)Seed-bearing fruit possesses prickly thorns. Easily sticks to wool and clothes Yes Yes DEPI-AU, 2014; Todd, 1882; Tower, 1906
Solenopsis invicta (red imported fire ant)Electrical equipment, vehicles - accidental Yes ISSG, 2014
Soliva sessilis Yes Yes Polster, 2007
Sonchus asper (spiny sow-thistle)Seeds in crop seed, feathers, fur, clothing, shoes, machinery Yes Yes Doty, 1961
Sonchus oleraceus (common sowthistle) Yes Yes Holm et al., 1977
Sphaerodactylus vincenti (Saint Vincent dwarf gecko)Possible invasion pathway by humans Yes Daltry, 2009
Sporobolus africanus (rat’s tail grass)attaches to clothes, vehicles, animals Yes Yes
Sporobolus pyramidalis (giant rat’s tail grass) Yes
Sporobolus pyramidatus (whorled dropseed) Yes Wester, 1992
Taeniatherum caput-medusae (medusahead wildrye) Yes Yes Kyser et al., 2014
Tapinoma melanocephalum (ghost ant)In all the reported interceptions, it is associated as a hitchhiker with equipment or a crop Yes Yes Harris et al., 2005
Thaumastocoris peregrinus (bronze bug)Unintentional movement of both extreme long distances and locally principally through human mediatio Yes Yes Nadel et al., 2010
Theba pisana (white garden snail) Yes Yes Cowie, 1987; Robinson, 1999
Themeda quadrivalvis (grader grass)Contaminant in straw packing, hay, pasture seed and birdseed Yes Yes Doty, 1961
Tibouchina herbacea (cane tibouchina)Found on tree tern trunks imported to Oahu from Hawaii island. A likely contaminant of potted plants Yes Yes Frohlich and Lau, 2007
Tibouchina urvilleana (princessflower)Propagules are likely to be dispersed unintentionally, because plants growin heavily trafficked area Yes PIER, 2016
Tithonia diversifolia (Tithonia)Contaminant in food aid Yes Akobundu and Agyakwa, 1987
Trapa natans (waterchestnut) Yes Yes Les and Mehrhoff, 1999
TropilaelapsOn bees or beekeeping equipment moved for apicultural purposes. Yes Yes Defra, 2005
Tubastraea coccinea (orange-cup coral) Yes Yes
Typha domingensis (southern cattail)Achenes with hairs attach to humans and animals. Yes Yes Parsons and Cuthbertson, 1992
Typha x glauca (hybrid cattail)Fruits and hairs attach to humans, animals and farm implements Yes Parsons and Cuthbertson, 1992
Tyto alba (Barn owl)On ships and aircraft Yes Hyde et al., 2013
Ulva pertusa Yes Carlton, 1985; Hewitt et al., 2007; Sidharthan et al., 2004
Umbra pygmaea (eastern mudminnow)Belgian pisciculturists unintentionally spread U. pygmaea in several ponds in Marne region (France) Yes Guidou and Keith, 2002; Verreycken et al., 2010
Undaria pinnatifida (Asian kelp) Yes Forrest et al., 2000; Voisin et al., 2005
Urochloa distachya (signal grass)Seed contaminant Yes Yes New Zealand Ministry for Primary Industries, 2015
Urtica dioica (stinging nettle) Yes Yes Taylor, 2009
Ventenata dubia (North Africa grass)Seeds easily transported by animals, when seeds are present Yes Yes
Verbascum thapsus (common mullein) Yes PIER, 2014
Verbena litoralis (blue vervain) Yes Yes
Vespa velutina (Asian hornet) Yes Yes
Vespula germanica (German wasp)Europe to New Zealand, New Zealand to Australia, within Australia Yes Yes Spradbery and Maywald, 1992; Doty, 1961
Vespula pensylvanica (western yellowjacket)Christmas tree trade Yes Yes
Vespula vulgaris (wasp, common) Yes
Vulpia myuros (annual fescue)Seeds attach to animals, machinery etc. Accidental. Yes Yes Wallace, 1997
Wasmannia auropunctata (little fire ant)On camping equipment Yes Doty, 1961
Xanthium spinosum (bathurst burr) Yes Yes PIER, 2013
Xenohaliotis californiensisTransport of infected abalones Yes Yes Crosson et al., 2014
Zachrysia provisoria (Cuban brown snail)Occasional, accidental Yes Yes Robinson and Fields, 2004
Zinnia peruviana (Peruvian zinnia)Seeds have awns that attach to fur and clothing Yes Yes Torres, 1963