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
Aeginetia indica (forest ghost flower)Not mentioned in references but could be a possible way of seed movement 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 palmeri (Palmer amaranth)Moved unintentionally with crop products, machinery, clothing Yes Yes Ward et al. (2013); EPPO (2019)
Amaranthus tuberculatus (rough-fruited water-hemp)Can adhere to farm machinery Yes Costea et al. (2005)
Ambrosia confertiflora Yes
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 Schrader and Schröder (2013); Blank et al. (2014)
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 Mararuai et al. (2002)
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
Bagrada hilaris (painted bug) Yes Yes Matsunaga (2014); LeVeen and Hodges (2015)
Bassia hyssopifolia (fivehook bassia) Yes Yes
Batrachochytrium salamandrivorans (Bsal)Possible human-mediated (direct) dispersal by pathogen adherence to boots or shoes Yes Martel et al. (2014)
Bergia capensis (white water fire)Possible on clothes, shoes or equipment used in rice fields, in debris from rice cultivation, or in mud attached to feathers and feet of birds Yes Yes Leach (1989); Quiles Hoyo (2019); India Biodiversity Portal (2019)
Bidens frondosa (beggarticks) Yes Online Atlas of British and Irish Flora (2014)
Blattella germanica (German cockroach) Yes Yes Rockman (1992)
Boa imperator (Central American Boa)Accidental as stowaway in cargo Yes Guthrie (1923); Allen (1928)
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 Cal-IPC (California Invasive Plant Council) (2016)
Brachypodium sylvaticum (slender false brome) Yes Yes Heinken and Raudnitschka (2002)
Brassica nigra (black mustard)accidental Yes Yes Cal-IPC (California Invasive Plant Council) (2004)
Brassica rapa (field mustard)Possible from its cultivation and as part of bird food mix Yes Vibrans (2018)
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)
Candidatus Liberibacter africanus (African greening)Infected vectors on leaf debris and hosts plants Yes Yes
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
Cassytha filiformis (love-vine)Seeds are dispersed by birds and mammals Yes Yes Weber (1981); Nelson (2008)
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
Ceratopteris thalictroides (watersprite)Possibly arriving in Hawaii through rice (Oryza sativa) crops Yes Yes Lloyd (1973)
Chama macerophylla (leafy jewelbox) Yes Yes
Channa argus argus (northern snakehead) Yes Yes Courtenay and Williams (2004)
Chloris gayana (Rhodes grass)Seeds as contaminants (pasture seeds) Yes Yes Weeds of Australia (2020)
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)
Coptotermes gestroi (Asian subterranean termite)Hitchhike on any wooden structure e.g. storage boxes Yes Yes
Corella eumyota (orange-tipped sea squirt)Hull fouling, floating debris, contaminated mussels or oysters Yes Yes Lambert (2004); 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)
Cucurbit aphid-borne yellows virus (Cucurbit aphid-borne yellows)Possible through movement of infected seedlings or fruit for human consumption (rare to very rare, accidental) Yes Yes
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)
Dichanthium aristatum (angelton bluestem)Although no detailed information available it is reported as a potential seed contaminant Yes Yes USDA-ARS (2020)
Didemnum vexillum (carpet sea squirt) 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 Catasús Guerra (2015)
Digitaria fuscescens (yellow crab grass)Might be carried unintentionally in clothes, shoes, etc Yes
Diplazium esculentum (vegetable fern)Possible in mud attached to animals Yes HEAR (2020)
Diplodia seriata (grapevine trunk disease) 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
Drymaria arenarioides (alfombrilla)Spread by adhering to animals Yes Allison (1977)
Echinochloa crus-pavonis (gulf cockspur grass)Contaminated agricultural equipment moved from field to field Yes Webster (2015)
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 Christy et al. (2007); Jensen et al. (2008); Olson et al. (2012); Reynolds (2012); Schwartz (1974); Stewart (1977); Zippel et al. (2005)
Elodea canadensis (Canadian pondweed) Yes Yes
Emilia praetermissa (yellow thistle)Seeds dispersed as contaminants Yes Yes PROTA (2020)
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 Reis (1993)
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)
Eriocheir hepuensis (Hepu mitten crab) Yes Naser et al. (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)
Euwallacea fornicatus (polyphagous shot-hole borer)Usually transported in wood packaging material Yes
Faxonius limosus (Spiny-cheek crayfish)Fishing nets or shipments of fish for stocking Yes
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)
Funtumia elastica (West African rubber tree)Possible that seeds could hitchhike in clothes, gear and vehicles Yes
Galega officinalis (goatsrue) Yes
Geosmithia morbida (thousand cankers disease)Walnut wood or wood products Yes 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)
Helenium amarum (bitterweed)Potentially accidentally carried by aircraft Yes Tomley and Panetta (2002)
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 spicigera (black sesame) Yes Yes Le Bourgeois et al. (2019)
Hyptis suaveolens (pignut) Yes Cullen et al. (2012)
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
Ipomoea quamoclit (cypress vine)Seeds in garden waste Yes Australian Tropical Rainforest Plants (2010)
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)
Kigelia africana (sausage tree)Vertebrates eat the fruits and disperse the seeds Yes SANBI (2020)
Lactuca floridana (woodland lettuce) Yes Yes
Lagarosiphon major (African elodea) Yes USDA-ARS (1997)
Lampropeltis californiae (California kingsnake)Stowaways on ships Yes Yes Verzelen et al. (2017)
Lemna aequinoctialis (lesser duckweed)Short distance by birds and fish Yes Hicks (1937)
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 Online Atlas of the British and Irish Flora (2016)
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
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)
Lycorma delicatula (spotted lanternfly)Adults frequently land in vehicle conveyances and can be transported long distances Yes Yes
Lygodium japonicum (Japanese climbing fern)Spores spread when pine straw collected from infested sites and used as mulch elsewhere Yes Loan van (2006)
Lythrum maritimum (pukamole)Seeds can be transported on vehicles or clothing Yes Yes Anderson et al. (1992)
Maconellicoccus hirsutus (pink hibiscus mealybug) Yes Yes Harman (in press)
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 Klein (2011); USDA-NRCS (2017)
Melissococcus plutoniusOn apiculture products or equipment Yes
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); Native Turf as Grass (2010)
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)
Monochoria hastata (hastate-leaved pondweed)No information available, but possible from rice cultivation practices Yes
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)
Mytilus galloprovincialis (Mediterranean mussel) Yes
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)
Nephrolepis hirsutula (sword fern)Possible in animal fur, and accidentally by people Yes Whistler (1988)
Nerium oleander (oleander)As a seed contaminant Yes Yes Hanelt (2020); USDA-ARS (2020)
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)
Papuana huebneri (taro beetle)Ships, boats, other vehicles, soil, gravel, water, taro corms and taro propagating material Yes Yes
Parentucellia viscosa (yellow glandweed) Yes Yes
Parthenium hysterophorus (parthenium weed)Animals, vehicles, machinery, grains, humans Yes Yes PAG (2000); Baiwa et al. (2016)
Paspalum dilatatum (dallisgrass)unintentionally dispersed by animals and humans Yes Yes Eurobodalla Shire Council (2017); PIER (2017)
Paspalum notatum (Bahia grass)garden waste, grass and crop seeds, hay and agricultural machinery Yes
Paspalum urvillei (Vasey grass)Mostly related to agricultural practices Yes Yes Hitchcock (1936); FAO (2012b)
Passion fruit woodiness virus (passionfruit woodiness disease)Moves in infected Passiflora plant material Yes Yes Baker et al. (2014)
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); Redondo et al. 2015)
Phytophthora cinnamomi (Phytophthora dieback)Probably very common Yes Yes
Phytophthora kernoviaeSoil harbouring pathogen transported on footwear, tools, machinery, etc. Yes Yes Benson et al. (2010); EPPO (2013)
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
Pseudelephantopus spicatus (false elephant’s foot) Yes Yes Ward (1975)
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)
Pteris tripartita (giant brake)Not mentioned in literature, but a possibility from its cultivation Yes
Pteris vittata (Chinese ladder brake fern)Spores can be transported via clothing and equipment Yes UF-IFAS Center for Aquatic and Invasive Plants (2019)
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 harrisii (Harris mud crab)On 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 Powell (1970)
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 Luneva (2009); Alien Plants of Belgium (2016)
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)
Solanum sisymbriifolium (sticky nightshade)Contaminant in fodder Yes Yes Hill (1994)
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 GISD (2018)
Sonchus oleraceus (common sowthistle) Yes Yes Holm et al. (1977)
Sphaerodactylus vincenti (Saint Vincent dwarf gecko)Possible invasion pathway by humans Yes Daltry (2009)
Spirodela polyrrhiza (giant duckweed)Moved over short distances accidentally attached to fur or feathers of aquatic animals Yes Les (2020)
Spodoptera eridania (southern armyworm)Movement of plants, interceptions Yes Yes
Sporobolus africanus (rat’s tail grass)attaches to clothes, vehicles, animals Yes Yes
Sporobolus junceus (pineywoods dropseed)Possible movement by small animals that use the species as a food source Yes USDA-NRCS (2020)
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)
Tagetes erecta (Mexican marigold)Seeds adhered to animals Yes Yes Cortés-Flores et al. (2013)
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 Keir and Vogler (2006)
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 (Mexican sunflower)Contaminant agricultural produce Yes Akobundu and Agyakwa (1987)
Tragus racemosus (stalker bur grass)Accidentally introduced to various countries as a contaminant of wool products Yes Yes Alien plants of Belgium (2020); SEINet (2020)
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
Verbena officinalis (vervain)Found in ballasts and established in dump grounds Yes Yes Brown (1878)
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); Thomas (1960)
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 ISSG (2014)
Xanthium spinosum (bathurst burr) Yes Yes PIER (2013)
Xenohaliotis californiensisTransport of infected abalones Yes Yes Crosson et al. (2014)
Youngia japonica (oriental false hawksbeard)Contaminant in crop and grass seeds or soil Yes Yes USDA-NRCS (2018)
Zachrysia provisoria (Cuban brown snail)Occasional, accidental Yes Yes Robinson and Fields (2004)
Zeuxine strateumatica (soldier’s orchid)Accidentally introduced with contaminated seeds, soil, footwear and animals Yes Yes Ames (1938); Proctor (1982)
Zinnia peruviana (Peruvian zinnia)Seeds have awns that attach to fur and clothing Yes Yes Torres (1963)