Mites and ticks ( Acari ) Chapter 7 . 4

Th e inventory of the alien Acari of Europe includes 96 species alien to Europe and 5 cryptogenic species. Among the alien species, 87 are mites and 9 tick species. Besides ticks which are obligate ectoparasites, 14 mite species belong to the parasitic/predator regime. Among these species, some invaded Europe with rodents (8 spp.) and others are parasitic to birds (2 spp). Th e remaining 77 mite species are all phytophagous and among these 40% belong to the Eriophyidae (37 spp.) and 29% to the Tetranychidae (27 spp.) families. Th ese two families include the most signifi cant agricultural pest. Th e rate of introductions has exponentially increased within the 20th century, the amplifi cation of plant trade and agricultural commodities movements being the major invasion pathways. Most of the alien mite species (52%) are from North America, Asia (25%), and Central and South America (10%). Half of the ticks (4 spp.) alien to Europe originated from Africa. Most of the mite species are inconspicuous and data regarding invasive species and distribution range is only partially available. More research is needed for a better understanding of the ecological and economic eff ects of introduced Acari.


Introduction
Th e subclass Acari, which includes mites and ticks, forms an important part of the class Arachnida, with a worldwide distribution and with over 55,000 (Krantz and Walter 2009) species described to date.An estimate of up to half a million to a million more species await discovery (Krantz and Walter 2009).Mites and ticks are a very diverse group ranging in size from about 0.08 mm up to 1 centimetre long.Acari diff er from others Arachnida by the fusion of the abdominal segments as in Araneae (spiders) and from spiders by the presence of a gnathosoma containing mouthparts, the fusion of the posterior part of the prosoma (the podosoma, bearing legs) and fusion of an opisthosoma into an idiosoma (Evans et al. 1996).Most species are free living and have diff erent trophic modes, including phytophagous, predators feeding on a variety of small invertebrates, fungivores and detritivores.Some species have developed complex parasitic relationships with both vertebrate and invertebrate animals.A number of acarine groups are injurious to crops and to livestock, both because of their feeding activities and because of their capacity as vectors for a variety of disease organisms to their plant or animal host.While the Oribatida is an important group (more than 6,000 species) having a key role in soil equilibrium, data regarding invasive species and distribution range remain largely unavailable.Ticks are very peculiar acarines, since they are obligate ectoparasites.In this sense they form a very homogenous group, with the order Ixodida composed of only three families.In this chapter, the two groups of Acari, mites and ticks, will be treated separately.Th e ticks will be presented through the description of a few signifi cant case studies.By contrast, mites being much diversifi ed in their biology and habitat use, and being truly ubiquitous, will be presented systematically.
Mites have successfully colonized nearly every known terrestrial, marine, and freshwater habitat.Th e most studied and observed invaders are found among the phytophagous mites of the families Tetranychidae and Eriophyidae, which include important agricultural pests.Th ere is a growing awareness of the economic relevance of eriophyids as crop pests, including their importance as vectors of plant viruses, their role as alternative food for predators of plant pests, and their potential as weed control agents (Sabelis and Bruin 1996).A description on spider mite biology and their control is presented in the extensive review by Helle and Sabelis (1985).In addition to plantfeeding mites, a second group includes the alien parasitic mites.Among them, some invaded Europe with rodents such as muskrats (six alien species of mites), and brown rats (two aliens), while others are bird parasites (two species).Dermatophagoides evansi (Pyroglyphidae) is not associated with rodents and it has probably been accidentally introduced by humans (Bigliocchi and Maroli 1995,Hughes 1976,Th ind and Clarke 2001).A single species in the family Varroidae, Varroa destructor, is alien to Europe (De Rycke et al. 2002, Griffi ths andBowman 1981).
Ticks are important parasites of livestock, wild animals, and humans.After their parasitic phase, they spend most of their life cycle outside their hosts, where prevailing climate conditions may constrain their ability to colonize a given territory.While some tick species are highly restricted to particular combinations of climatic variables, or have defi ned host species, others may occur in widely variable climate conditions and have catholic feeding habits.Some species of ticks can be considered as invasive species, since the uncontrolled movements of domestic animals may introduce alien species into Europe or disperse some species outside their native distribution ranges.Th e introduction via large-bodied host vectors (such as passerine birds) and the uncontrolled importation of reptiles, are important means for colonizing newly available areas.Furthermore, one species of tick, Rhipicephalus sanguineus, is spreading in parts of Europe out of its current range because of the movements of domestic dogs.

Taxonomy of the mite species alien to Europe
A total of 101 mite species have been considered as alien to Europe, including 96 species shown to have originated from other continents and 5 cryptogenic species (Table 7.4.1).Th ese species involve 16 diff erent families of mites (Figure 7.4.1).In addition, Table 7.4.2provides some examples of mite species alien in Europe; i.e., European species introduced from one part of Europe to another where they are not native.
Alien mites belong to two super orders, Acariformes (Actinotrichida) and Parasitiformes (Anactinotrichida).Most of these species belong to two orders of Acariformes, Prostigmata and Astigmata.Prostigmata includes the three most important superfamilies: * Tetranychoidea comprises two main families containing alien mites.Th e Tetranychidae family, or spider mites, includes 1,250 described species (http://www1.montpellier.inra.fr/CBGP/spmweb/).Among them, 100 can be considered as pests and 10 as major pests of agricultural crops.All stages are phytophagous and feed on parenchyma cells.No viruses associated with spider mites have been observed.Th e most widely distributed species is the highly polyphagous and ubiquitous Tetranychus urticae (two spotted spider mite), found on nearly 1,000 plant species.In Europe, alien spider mites are generally more specialized and occur on a single genus or family of plants.Due to their minute size (200 to 900 μm) typical of many species of Acari, spider mites remain undetected until major plant damage occurs.Th e members of another family, Tenuipalpidae, or false spider mites, are important obligate phytophagous mites.Th ey are elongate, dorsoventrally fl attened and usually have a reddish colour.
* Eriophyoidea includes three families: -Eriophyidae, to which belong ca.88% of all known Eriophyoidea in the fauna of Europe (Fauna Europaea 2009).Th ese are vermiform, four legged mites.Th e family includes important economic pests of broadleaved plants.All known mite vectors of plant pathogens and nearly all gall-forming species belong to this family.About half are vagrants.Most of the species in the genera Aceria and Eriophyes cause specifi c galls on the leaves, green twig, fl ower buds, vegetative buds, or fruit of the hosts (Oldfi eld 1996).Others, especially Epitrimerus, Phyllocoptes, Aculops and Aculus cause discolouration and other non-distortive damage to their hosts.
-Phytoptidae, which are obligate phytophagous and gall mites, with a high degree of specifi city.Th ey are also vermiform and four-legged.Th e family Phytoptidae is well represented on conifers (half of the described phytoptid species) and monocots.Phytoptidae is less represented than Eriophyidae or Diptilomiopidae on dicotyledons.Four alien species out of a total of 56 species have been reported in the fauna of Europe.
-Diptilomiopidae, which are predominantly leaf vagrants, only inhabiting leaves of dicotyledons, and rarely causing notable damage to their hosts (Keifer 1975).Two monotypic genera are known from only two families of monocotyledons (Poaceae and Palmae) occurring in the tropics.Rhyncaphytoptus species are mainly represented on several families of deciduous trees in the Holarctic region.Two alien species have been reported, out of the total 61 in the European fauna.
* Tarsonemoidea represented by the family Tarsonemidae includes economically important mites.Most of them are mycophagous.Some species are phytophagous, whereas others are parasites of bark beetle eggs, or predators of tetranychid eggs.Th e most redoubtable pest species in the family is the broad mite, Polyphagotarsonemus latus (=Hemitarsonemus latus), which was described in 1890 and has recently been redefi ned and considered as being a species complex (Gerson 1992).
Th e order Astigmata is less represented in the alien fauna.A few species belong to the super-family Sarcoptoidea, and especially to families Listrophoridae and Myocopidae.Members of Listrophoridae are usually small, elongate mites and are skin or hair parasites of mammals.Th e palpae and/or legs I-II are often highly modifi ed for grasping hairs.Four species of Listrophoridae mites have invaded Europe, grasped to the fur of muskrats: Listrophorus americanus, L. dozieri, L. faini and L. validus (Šefrová and Laštůvka 2005).Myocopids, or hair mites, live on skin of marsupial and rodents (Bauer andWhitaker 1981, Šefrová andLaštůvka 2005,  Whitaker 2007).Myocoptes ondatrae is an ectoparasite that has invaded Europe by grasping the fur of muskrats (Bauer and Whitaker 1981, Šefrová and Laštůvka 2005, Whitaker 2007).Other species belong to the super-family Acaroidea and families Epidermoptidae and Pyroglyphidae.Epidermoptidae are skin parasites of birds.Epidermoptes bilobatus causes avian scabies.Pyroglyphidae are external parasites living on bird feathers or are nidicolous.Dermatophagoides evansi feeds on human detritus, and lives in house dust as well as within bird nests (Piotrowski 1990, Razowski 1997).
Among the super-order Parasitiformes (Anactinotrichida), aliens belong to orders Ixodida and Mesostigmata.Ixodida is represented by the species in the family Ixodidae, which is treated in a separate section at the end of the chapter.Alien Mesostigmata belong to superfamilies Ascoidea and Dermanyssoidea.Th e fi rst superfamily is represented by a single family with aliens, Phytoseiidae, which are predators of spider mites.In Europe, species such as Phytoseiulus persimilis, Amblyseius (Neoseiulus) californicus and Iphesius (Amblyseius) degenerans are used as biological control agents against phytophagous pests (Bartlett 1992, Croft et al. 1998, Easterbrook 1996, EPPO 2002, Garcia Mari and Gonzalez-Zamora 1999, Helle and Sabelis 1985, McMurtry and Croft 1997).Th ree families of Dermanyssoidea contain alien species.Varroidae mites are ectoparasites of honeybees.Varroa destructor is at present the most important parasite of Apis mellifera (L.).Varroa feeds on the haemolymph of adult, larval and pupal bees.Laelapidae mites live in soil, are nidicoles or parasitize small mammals and insects.Ondatralaelaps multispinosus is an ectoparasite of muskrats (Šefrová and Laštůvka 2005).Laelaps echidninus is a common worldwide ectoparasite of spiny rats, wild brown rats and is occasionally found on the house mouse and cotton rat (Wharton and Hansell 1957).Macronyssidae mites are haematophagous, have a large dorsal shield, prominent chelicerae and inconspicuous body setae (Easterbrook et al. 2008).Ornithonyssus bacoti is a parasite of rats, living in rat nests and their surroundings (Cole et al. 2005, Easterbrook et al. 2008, Fan and Petit 1998, Whitaker 2007).Ornithonyssus bursa is a natural parasite of common birds including pigeons, starlings, sparrows, Indian mynahs, poultry, and some wild birds, such as the robin (Berggren 2005).

Temporal trends of introduction in Europe of alien mite species
Th e rate of arrival of alien mites in Europe is increasing exponentially (Figure 7.4.2).An average of 2.1 alien species was newly recorded per year in Europe during 2000-2007 whereas only half this number was recorded during the period 1950-1974 (1 species/year).However, large diff erences were found between families.
Th e fi rst records for Europe of all alien Tetranychidae are extensively documented in this chapter.Th ere are no records reported before 1950; however, only few taxonomists were specialized on the family before this date.Since the second half of the 20 th century, tetranychid species have been reported at an average rate of one new species every two years, with an acceleration of reports (one species per year) since 2000.
Most of these mites represent agricultural pests, and therefore have been widely studied which explains the overrepresentation of crop pest species as Tetranychidae aliens.
Th e mean number of records of Eriophyoidae species alien to Europe increased rapidly during the third quarter of the 20 th century.Only one species Aceria alpestris, which is alien in Europe, was recorded within the period 1850-1899.Th is species was described from the host plant Rhododendron ferrugineum L. from Tirol (Austria).Th e species was later recorded in mainland Italy, Czech Republic, Slovenia and Serbia, but it is not clear if it was associated with cultivated Rhododendron.Species recorded intensively between 1900-1924 (although described from Germany in 1857) are categorized as cryptogenic ( Eriophyes pyri, the pear blister mite) or alien in Europe, like Aculus hippocastani (recorded in 1907, but probably introduced in Europe from the 17 th century when its host plant Aesculus hippocastanum L. was intensively cultivated), and Aceria loewi (probably introduced in the 16 th century when lilac started to be cultivated in France).Aculops allotrichus, which is alien to Europe, was recorded in 1912 but was probably, introduced with its host Robinia pseudoacacia L. which was for the fi rst time introduced into France at the beginning of 17 th century.Aceria erinea and A. tristriata were suspected to have an Asian origin and have been designated as aliens.Th ey were recorded on 1903, but probably were present on its host, Persian walnut, in the Balkans and South Europe much earlier.Only one species in the Eriophyoidae was recorded between 1925-1949, e.g.Aceria petanovicae, the lilac rust mite.Being for long time known under the name of Aculops massalongoi the species is alien in Europe.Six alien species to Europe were recorded between 1950-1974.Two pests of citrus, Aceria sheldoni (citrus bud mite) and Aculops pelekassi (citrus rust mite) and the azalea mite Phyllocoptes azaleae, are suspected to have been introduced from Asia.Characteristic symptoms of deformed lemon fruits caused by A. sheldoni were drawn by Battista Ferrari in Italy in 1664 (Ragusa 2002).Th ree pests have been reported from North American maple trees (Acer negundo L., A. saccharinum L. and A. rubrum L.), i.e.Shevtchenkella brevisetosa, Vasates quadripedes and Rhyncaphytoptus negundivagrans.Th e 25 species recorded during the period 1975-1999 almost all have a North American origin (only Epitrimerus cupressi is designated as cryptogenic, because of the Mediterranean origin of its host Cupressus sempervirens L.).During the period from 2000 to 2007, one species alien to Europe, Rhyncaphytoptus bagdasariani, has been recorded as being introduced from Asia and the serious pest Aceria fuchsiae (a species on the European quarantine list) was introduced from South America.As for other phytophagous mites, the most probable explanation for the acceleration in the pace of introductions of alien eriophyids is intensifi cation of international trade.Most of these alien species inhabit ornamental trees and shrubs, fl owers and potted ornamental plants.
Some alien parasitic mites have invaded Europe with rodents such as muskrats and brown rats.Th e muskrat (Ondatra zibethicus L.) is an invasive rodent native to North America.It was introduced around 1905, by humans as a fur resource in several parts of Europe, as well as in Asia and South America.Six species of mites, native from North America (Bauer andWhitaker 1981, Whitaker 2007), have invaded Europe grasping its fur (Glavendekić et al. 2005, Šefrová andLaštůvka 2005).Th e fi rst report of muskrat mites was recorded in 1955, and a second in 2000, both in Czech Republic.Two other parasitic species, Laelaps echidninus and Ornithonyssus bacoti, are also alien ectoparasites of rodents that have invaded Europe and were identifi ed in the 1950's (Šefrová and Laštůvka 2005), but the exact pathway of introduction is not known.One possible vector is the wild brown rat, Rattus norvegicus (Berkenhout).Th ought to have originated in northern China, this rodent spread in Europe in the middle ages and is now the dominant rat in the continent.
Birds are vectors of a second group of alien parasitic mites, that include Epidermoptes bilobatus and Ornithonyssus bursa, both identifi ed in the 1950's, in the Czech Republic (Šefrová and Laštůvka 2005).Th e exact route of introduction is not known with confi dence, but a possible vector is the chicken (Gallus gallus domesticus L.).In the 20 th century, with the intensifi cations of poultry production, concerns have been raised about the increasing risk of transfer of diseases and mites (from chickens to native bird species).
Whereas the exact date of arrival of alien mites is generally unknown, deliberately released biological control agents are the exception to this rule.Among them, three phytoseiids are mainly used as predatory species against pests (McMurtry and Croft 1997).Phytoseiulus persimilis was introduced for the fi rst time in the 1970's in Bulgaria andCzech Republic (EPPO 2002, Šefrová andLaštůvka 2005).Neoseiulus californicus was introduced for the fi rst time in 1991 in Great Britain (EPPO 2002).It was also introduced at the same period in the Czech Republic (EPPO 2002, Šefrová andLaštůvka 2005).Th e third introduced mite is Iphiseius degenerans.It is native from the Mediterranean region and was introduced for the fi rst time in 1993 in Czech Republic (EPPO 2002, Šefrová andLaštůvka 2005).Nowadays, these three biological agents have been introduced in most European countries.

Origin of the mite species alien to Europe
Figure 7.4.3.presents the region of origin of the 101 alien species of mites.Most of the alien mite species (52%) came from North America, then from Asia (25%), and Central and South America (10%).Th e origin of phytophagous alien mites can usually be inferred from the origin of the host plant.Th ese mites are dispersed over long distances mainly by the introduction of plant material and spread further by plant cultivation in newly colonized regions.Aerial distribution is possible and most frequent, but mainly over short distances (Margolies 1993, Margolies 1995).In the case of highly polyphagous species such as several Tetranychidae, their ubiquity and highly diverse host uses might be misleading and the origin can be diffi cult to ascertain.Twelve out of 27 alien Tetranychidae originated in North America, nine in Asia and only fi ve in Central and South America.Temperate regions provide the majority of the alien species (16 vs. 11 for tropical areas).
Th e majority of eriophyoid species are mono-or oligophagous and are distributed within the host range.North America appears to be the dominant source of the alien eriophyoid fauna with half of the species originating from this continent.Around 26% of species originate from Asia, and less than 10% from South America.A few species are designated as cryptogenic or with questionable origin.For example, Rhyncaphytoptus negundivagrans, although described from Hungary, probably originated from North America with its host plant, Acer negundo.Whereas the camellia rust mite, Cosetacus cameliae (described from California) was probably introduced to Europe from the USA, it probably has an Asian origin considering that Camelia japonica L. comes from subtropical and tropical regions of Southeast Asia.Th e pouch gall mite of plum leaves, Eriophyes emarginatae, fi rst discovered in the USA, has also been recorded in Serbia and Japan.Th is mite is very closely related to the European E. padi (Nalepa) (Petanović 1997) and may even be the same species, with synonymous names (Keifer 1975).Epitrimerus cupressi was described from North America, but according to the origin of its host plant Cupressus sempervirens, which is from the Mediterranean region, the mite probably has an European origin too.Th e gall mite Phytoptus hedericola (Phytoptidae) is native from South Africa (Glavendekić et al. 2005), and Trisetacus chamaecypari (Phytoptidae) from North America (Ostojá-starzewski andHalstead 2006, Smith et al. 2007).
Among the false spider mites (Tenuipalpidae), Brevipalpus californicus, B. obovatus and Tenuipalpus pacifi cus originated from Central and South America, and Florida (USA) (Denmark 1968, Manson 1967).Six alien species of rodents bear parasitic mites originating from North America, and belong to the families Listophoridae (four species), Laelapidae (one species), and Myocoptidae (one species).In their native country, they are all ectoparasites of murskrats.Th ere are also some bird parasites: one species of Epidermoptidae, Epidermoptes bilobatus, is an ectoparasite native from South Asia, and Ornithonyssus bursa is probably native from Trinidad.
A single Varroa species, V. destructor, is alien to Europe (Griffi ths and Bowman 1981).Its native range is South East Asia, where it was originally confi ned on its original host, the Asian honeybee, Apis cerana F. Th is mite came to be a parasite of the European honeybee, Apis mellifera, in the mid-twentieth century.Importation of commercial A. mellifera colonies into areas with A. cerana brought the previously allopatric bee species into contact and allowed V. destructor to switch to the new host

Distribution in Europe of the alien mite species
Alien mite species are not evenly distributed throughout Europe.Large diff erences in the number of aliens are noticed between countries (Figure 7.4.4)but it may refl ect diff erences in sampling eff orts and in the number of local taxonomic specialists.
Among the Tetranychidae, 19 alien species are found around the Mediterranean Basin and 12 in the rest of Europe.With relatively warm winters, the Mediterranean region provides suitable climatic living conditions for many species of temperate climates, but also for the establishment of many species of tropical or sub-tropical origin.Except for Panonychus citri and the cryptic species Tetranychus ludeni, which can be found in glasshouses in Europe, all tropical alien spider mites are restricted to the area around the Mediterranean Sea.Most alien Eriophyids have a very restricted distribution.More than 40% of the species have been observed in only one country (17 species), more than 40% (21 species) in 2-5 countries, and approximately 20% (7 species) in 6-11 countries.Eight European countries have no recorded occurrence of alien eriophyoids to date.Only one species, the pear blister mite Eriophyes pyri (which has cryptogenic status), has been recorded from 32 European countries.Besides E. pyri, the more widely distributed eriophyoid species are: Aceria erinea, A. loewi, A. sheldoni, Aculops pelekassi and Eriophyes canestrini.Th e gall mite Phytoptus hedericola (Phytoptidae) entered Europe in 2002 and has been observed in Serbia (Glavendekić et al. 2005).Trisetacus chamaecypari (Phytoptidae) entered Europe in 2002 (Ostojá-starzewski andHalstead 2006, Smith et al. 2007).Th e status of Typhloctonus squamiger (Phytoseiidae), a poorly known phytophagous mite found on trees in Italy since 1991 (Rigamonti and Lozzia 1999), is questionable.
Th e distribution of biological agents belonging to the Phytoseiidae family is wellknown.Phytoseiulus persimilis is now present in nearly all of Europe (Table 7.4.1)(EPPO 2002).Neoseiulus californicus has been found in the same countries except Austria, Hungary, Morocco, Slovakia, Sweden and Turkey.Th e third introduced phytoseid mite, Iphesius degenerans, is also present in several countries (Table 7.4.1).
Th e broad mite Polyphagotarsonemus latus (Tarsonemidae) is now cosmopolitan.In Europe, it was reported for the fi rst time in 1961 and since then the mite has invaded almost all countries (Table 7.4.1)(CAB-International 1986, Fan and Petit 1998, Natarajan 1988, Parker and Gerson 1994); it is potentially now in all parts of Europe.
Th ree species of false spider mites (Tenuipalpidae) are major invaders in Europe.Brevipalpus californicus, found in 316 orchid and tree species of 67 genera and 33 families, was fi rst recorded in 1960 and is mainly observed in citrus trees around the Mediterranean basin (Denmark 1968, Manson 1967).Th e privet mite, Brevipalpus obovatus is found in 451 herb, ornamental and shrub species (19 genera, 55 families) (Manson 1967) has been recorded from Austria, Cyprus, France, Germany, Israel, Netherlands, Serbia and Spain (Manson 1967).Tenuipalpus pacifi cus (the Phalaenopsis mite) is found in greenhouses of Phalaenopsis orchids in Germany, Great Britain, Netherlands and Serbia (Denmark 1968, Manson 1967).
Th e introduced range of Varroa destructor is practically worldwide.It was fi rst reported in Eastern Europe in the mid-1960s and it has spread rapidly all over the continent.Two diff erent genotypes, characterized by mitochondrial DNA sequences, have spread as independent clonal populations (Solignac et al. 2005), the Korean and the Japanese haplotypes, the latter having been found, besides Asia, in the Americas only.

Pathways of introduction in Europe of alien mite species
Although colonisation routes are poorly documented for the Tetranychidae, it is known that many species travel with their host plant.Small organisms like tetranychids are easily transported with plant material (leaves and in bark crevices).Only fi ve species feed mainly on herbaceous plants ( Tetranychus evansi, T. macfarleni, T. sinhai, Schizotetranychus parasemus, and Petrobia lupini), whereas all other alien species in the family feed on perennial shrubs.
As for tetranychids, the horticultural and ornamental trade is probably the most important factor for accidental introductions of almost all species of alien Eriophyoidae.Just a few species of Eriophyoids are on European quarantine lists, as plants are rarely inspected for presence of these mites.Infested plant material is not regularly intercepted at borders even in the case of important pests such as the grape rust mite Calepitrimerus vitis (Nalepa) or the blackberry fruit mite Acalitus essigi (Hassan), which are frequently disseminated with plant seedlings.During recent decades more than 50% of aliens were imported with ornamental plants.Among eriophyids, which are obligate plant parasites, only one trophic group which is associated with weeds, can be subject to intentional introduction.Although these mites were recently nominated as potential agents for classical biological control of weeds (few species are imported for this purpose), they have not yet been used for this purpose in Europe.Four species of alien eriophyoids which were probably introduced along with their host plants may have the potential as biological control agents of serious alien weed pests.In particular, Aceria ambrosiae can be used against the allergenous weed Ambrosia artemisifolia L. that was imported into Europe from North America.
As for other phytophagous species, the broad mite Polyphagotarsonemus latus (Tarsonemidae) has mainly been dispersed by human activities, but also by wind or insect transfer.Movement by insects should not be neglected: this concerns almost only females that get attached to the legs of aphids and the whitefl ies Bemisia argentifolii (Bellows and Perring), Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) (Fan and Petit 1998, Natarajan 1988, Parker and Gerson 1994).
Intentional introductions of mites represent a low proportion of alien arrivals.Only three phytoseeid predators were introduced purposely for biological control and have established.Some of these biological control agents were released in the fi eld but others were fi rst released in glasshouses, and then escaped and became established outdoors.
International travel and commerce has facilitated the dispersal of Varroa destructor.Once established in a new region, the mite spreads using drifting, robbing, and swarming behaviour of the host.Human mediated varroa dispersion also occurs via apicultural practices.

Ecosystems and habitats invaded in Europe by alien mite species
Alien mites established in Europe predominantly live in agrosystems or anthropogenic environments (ca.92%; Figure 7.4.5).Th is is especially verifi ed in Tetranychidae and Eriophyidae.Among eriophyoids, some are present in man-made habitats, parks and gardens (22 species), agricultural lands (13 species), and greenhouses (10 species); very few species inhabit woodland and forest, costal, alpine or sub alpine habitats.Most alien species in this superfamily are leaf vagrants (13 species).Twelve species cause leaf galls, erinea* and leaf rolling, 11 cause leaf and/or fruit russeting or other type of discolouration, six live predominantly in buds causing bud galls, three species cause stunting of whole plants and/or plant organs and two cause fl ower and/or fruit deformations.Among the leaf gall makers, the most important horticultural pests are distributed in many European countries, such as E. pyri, A. erinea, A. tristriata or, such as A. fuchsiae which is on quarantine lists.Among the rust mites, only a few are important horticultural pests like A. theae, A. pelekassi and C. carinatus.Most species are pests of ornamental trees, shrubs or fl owering plants, having an important aesthetic impact on plants in parks and streets in most European towns and cities (i.e. A. gleditsiae, A.ligustri, A. petanovicae, S. strobicus, P. chrysanthemi), an exception being A. sawatch-ensae which inhabits weeds.Two Eriophyoids which cause plant stunting, A. paradianthi and T. califraxini, are important pests of ornamental plants and one species, A. ambrosiae, is a potential biocontrol agent against the alien weed Ambrosia artemisifolia.Two species which cause fl ower and/or fruit deformations, A. alpestris and A. sheldoni, are respectively pests of Rhododendron and citrus trees.
Th e broad mite Polyphagotarsonemus latus (Tarsonemidae) has a very short life cycle of a few days, damaging crops abruptly.Being highly polyphagous, the species has been reported on 57 plant families (Gerson 1992) both in open fi eld crops and in greenhouses.Th is is an important pest of crops and ornamental plants such as azaleas, castor bean, chillies, citrus fruits, cotton, cucumber, mango, papaya, pepper, potato, sweet potato, tea, tomato and winged bean (Gerson 1992, Glavendekić et al. 2005, Heungens 1986, Raemaekers 2001).Nevertheless, in Europe this mite is found mainly in greenhouses because the mite cannot survive winter conditions outdoors.
False spider mites (Brevipalpus spp.; Tenuipalpidae) present a risk of invasion in greenhouses.Brevipalpus obovatus (the privet mite) is found on ornamentals and shrubs like citrus and azaleas and could become of great importance in glasshouses for ornamentals (Childers et al. 2003a(Childers et al. , 2003b)).Tenuipalpus pacifi cus (the Phalaenopsis mite) is one of the rare monophagous mites in the family, but it is a very destructive pest of orchids under greenhouses, mainly because it has several generations per year and has a two-month life cycle (Denmark 1968, Manson 1967).A Pyroglyphidae mite, Dermatophagoides evansi, is a cosmopolitan free-living species, often encountered in synanthropic situations and has probably been accidentally introduced by humans (Bigliocchi andMaroli 1995, Hughes 1976).

Ecological and economic impact of alien mite species
Seven species of alien Tetranychidae are important pests.On citrus, four alien species are found: Panonychus citri, Eotetranychus lewisi (also on grapes) Eutetranychus banksi and E. orientalis, the last presently spreading to Southern Portugal and Spain from Huelva to Murcia and Alicante.Oligonychus perseae is found on avocado and produces very severe damage in southern Spain (Malaga, Granada and Huelva) and in the Canary Islands.Stigmaeopsis celarius is found on bamboos and causes important visual damage to these ornamental plants.Tetranychus evansi is found on solanaceous crops and can reach very high density as observed in France, Spain and Canary Islands.All these mites are present in the Mediterranean Basin, which appears to be the region most threatened by alien species.Only two of these species can be found outside the Mediterranean area: Panonychus citri, especially in glass-houses, and Stigmaeopsis celarius.
In humid citrus-growing regions of the world, eriophyoid mites are considered to be the major mite pests (Jeppson et al. 1975, McCoy 1996).Two alien species, Aceria sheldoni and Aculops pelekassi, distributed worldwide, are among the most important pests infesting citrus.Th e pear blister mite, Eriophyes pyri, widely distributed in Europe, probably does little harm to the tree, but in severe infestations, the tree leaves may become disfi gured, and most importantly the mite may damage fruits (Easterbrook et al. 2008).Besides fruit orchards, species in the superfamily inhabiting wild trees in natural forests are: Aceria tristriata and A. erinea which appear to be the most common and most injurious eriophyoids found on Juglans regia L. (Castagnoli and Oldfi eld 1996).Among the fi ve species of eriophyoid mites reported from commercially important beverage crops in diff erent parts of the world, wherever tea is grown, the purple tea mite Calacarus carinatus and the pink tea mite Acaphylla theae are economically important in Southeast Asian countries, and in India (Channabasavanna 1996).Both species are aliens to Europe, reported from mainland Italy (A. theae) and from Hungary, Poland and Spain (C.carinatus).Records concerning host plant range in the case of C. carinatus are, besides tea, Viburnum opulus L. and Capsicum annuum L. (Amrine and Stasny 1994).Bearing in mind that congeneric Calacarus citrifolii has an extremely wide host range (Oldfi eld 1996), this might be also the case for C. carinatus, which would convey on the latter serious pest status in Europe.Economic impact of alien pest species of eriophyoids on ornamentals has been observed for Aculops gleditsiae on honey locust, Aceria petanovicie on lilac, Aculops ligustri on privet hedges, Aculops allotrichus on black locust, Reckella celtis on Celtis australis L., Shevtchenkella brevisetosa on Acer negundo, Vasates quadripes on silver maple, Phytoptus hederae on English ivy, and Setoptus strobicus on Pinus strobus L. (Petanović 2004).Flower and foliage aesthetic impact has been observed indoors (business centers, restaurants, shopping centers, hotels, etc.) for a few alien eriophyoids, Cecidophyopsis hendersoni causing a powdery appearance on Yucca leaves, Cosetacus cameliae causing bud rust and abortion on fl ower buds of Camelia plants, and Paraphytoptus chrysanthemi causing deformed buds, hairy leaves and rust on Chrysanthemum (Petanović 2004).Th e broad mite Polyphagotarsonemus latus (Tarsonemidae) and the false spider mites (Brevipalpus spp.) (Tenuipalpidae) are major pests of great agronomical impor-tance because of their broad host range, worldwide distribution and economic impact (CAB-International 1986, Fan and Petit 1998, Gerson 1992, Heungens 1986, Natarajan 1988, Parker and Gerson 1994, Raemaekers 2001).Th e most important threat for Brevipalpus spp. is the spread of citrus viruses (Childers et al. 2003b).
Among parasitic mites, the hair mites (muskrat mites) are currently considered non-pathogenic for humans although they are sometimes found in the fur of other mammals.Laelaps echidninus (Laelapidae) is a common worldwide ectoparasite of the spiny rats (hystricognath rodents), wild brown rat and is occasionally found on the house mouse, cotton rat and other rodents.It is a bloodsucking mite and the natural vector of Hepatozoon muris Balf.(Protozoa, Adeleidae), a haemogregarine parasite pathogenic for white rats (Smith et al. 2007) but which should not be overlooked as a possible vector of disease to humans (Wharton and Hansell 1957).Ornithonyssus bacoti (Macronyssidae) is a parasite of rats and inhabits the area in and around the rat's nesting area.Th is mite is the only one of the common rat mites which frequently deserts domestic rats to bite man or his domestic and laboratory animals (Cole et al. 2005).It is also a bloodsucking mite and its bite is painful and causes skin irritation, itching and skin dermatitis in humans (James 2005).Ornithonyssus bacoti, is a known vector of the murine fi larial nematode Litomosoides carinii Travasaos.In addition, it is susceptible to the transmission of endemic typhus, Rickettsia typhi (Wolbach and Todd) 1943 (= R. mooseri Monteiro) to humans (Berggren 2005, Bowman et al. 2003).
Epidermoptes bilobatus (Epidermoptidae) is a bird parasite causing avian scabies.Th is endoparasite burrows into the skin causing infl ammation and itchiness.Th e skin thickens with brownish-yellow scabs, which may become secondarily infected with a fungus.It is diffi cult to control and can cause death.Culling infested birds is usually required (Department of the Environment and Heritage 2006).Ornithonyssus bursa (Macronyssidae) is an haematophagous natural parasite of common birds including pigeons, starlings, sparrows, Indian mynahs, poultry, robin (Berggren 2005).Th ese pest mites and parasites are and will remain a long term problem for poultry housing (Gjelstrup and Møller 1985).Although none of these two species of mites are truly parasitic on humans and pets, they readily bite humans and are liable to cause allergies and dermatitis in human (Denmark andCromroy 2008, James 2005).Dermatophagoides evansi (Pyroglyphidae), and a species alien in Europe, Glycyphagus domesticus (Glycyphagidae), have been accidentally introduced by humans and often encountered in synanthropic situations (Bigliocchi and Maroli 1995, Hughes 1976, Th ind and Clarke 2001).Glycyphagus domesticus also occurs in bird, bat and mammal nests.It is associated with moist and humid conditions that promote the growth of mould on which they feed (Th ind and Clarke 2001).Dermatophagoides evansi (Pyroglyphidae) feeds on detritus and is also found in house dust, birds' nests and poultry houses (Piotrowski 1990, Razowski 1997).Dermatophagoides evansi represents a source of airborne allergens in indoor house dust (Eriksson 1990, Musken et al. 2000) that may cause sensitization, dermatitis, rhinopharyngitis and asthma especially among farmers.
Th e honeybee ectoparasite Varroa destructor causes serious losses through feeding injury in apiaries in Europe but also almost worldwide.While the populations of the parasite reach only a small size within colonies of A. cerana and do not damage the colony, infested A. mellifera colonies die.Th e problems with varroa control are typical of those encountered in curbing arthropod pest population.Varroas are becoming resistant to the acaricides used by beekeepers to control them.Th e recent discovery in several parts of the world (notably the United States of America (Harbo and Harris 2005) and Europe (Le Conte et al. 2007)) of honeybee bee colonies able to tolerate heavy infestations of V. destructor opens the door to lasting solutions for controlling the parasite.

Alien tick species: case studies
It is diffi cult to ascertain if a tick may have permanent populations outside of its native range or, to the contrary, they are just isolated records.In some cases, a few examples of a given species have been reported for a small area or found over non-resident hosts.Th is may result from the introduction of a few specimens, commonly immature stages.Th e most important means of introduction and expansion of ticks (provided that suitable climate and host is available) is by means of engorged females, because of their huge potential to lay thousands of eggs.
Th e movements of domestic ungulates have introduced some tick species, that may be considered to produce permanent and viable populations out of their native range.An example is the introduction of Hyalomma dromedarii into the Canary Islands, by the importation of dromedaries (Camelus bactrianus L.).Th e native range of this tick is northern Africa where C. bactrianus is the main adult host, and H. dromedarii is abundant in wide areas of Mauritania and Morocco.Th e current population of dromedaries in the Canary Islands was introduced from Morocco at the end of 18 th Century, and it seems that this tick came into these islands using dromedary hosts.H. dromedarii may use a wide range of hosts in immature stages, thus increasing risk of spread and permanent establishment (Apanaskevich andHorak 2008, Apanaskevich et al. 2008).It is diffi cult, however, to assess the reliability of records of Hyalomma anatolicum excavatum.A recent review of the original two subspecies (H.a. anatolicum and H. a. excavatum), concluded that they should be considered as separate species, although the matter is hard to decide as both taxa have a well defi ned allopatric range (Apanaskevich 2003).H. excavatum is restricted to central and eastern Asia and H. anatolicum colonizes wide areas of northern Africa.Th e records of H. excavatum from Bulgaria, Albania, Greece, and Italy should be cautiously treated, as they may probably represent H. anatolicum imported from northern Africa with domestic ungulates, as is the case for Hyalomma detritum.Th e formerly recognized species H. detritum, restricted to northern Africa, is now considered to be a synonym of the European H. scupense, which occurs not only in scattered localities of mainland Europe but is present in wide areas of northern Africa.Similarly, caution should be also applied for the single record of Hyalomma truncatum in the Canary islands.Th is tick is currently known to be restricted to parts of Asia, while a close species, H. rufi pes, is common in sub-saharan Africa.While the adults of H. rufi pes feed on a variety of hosts, including domestic ungulates, the immature stages commonly attach to diverse passerine birds.Most of these birds perform long distance travel in their migratory fl ights from Africa to Europe, and they have been found carrying hundreds of immature ticks (Hoogstraal 1956).However, as mentioned above, it is diffi cult for a population of nymphs to produce a viable and permanent population of resident ticks.To our knowledge, H. rufi pes has been recorded only in Cyprus and Macedonia (Apanaskevich and Horak 2008), and we still do not know if these are permanent populations or only accidental records on their passerine hosts on migration to lower latitudes from sub-saharan Africa.
Th e scenario for the tortoise tick, Hyalomma aegyptium, is however diff erent.Its presence outside northern Africa has been reported in countries such as Romania, Spain, Italy, Greece, Bulgaria, Croatia, and even farther north in Belgium (Siroky Pet al. 2007).Th e tick has permanent populations in areas of southern Russia (Robbins et al. 1998).Th ere have been also introductions of this tick by tortoises imported form northern Africa or eastern Europe, where this tick is common.Th e only record of a permanent population of H. aegyptium as a consequence of an accidental importation recorded for eastern Spain (Brotóns and Estrada-Peña 2004).Since the ticks attach to portions of the neck and legs of the host body, it may be diffi cult to fi nd feeding stages even after careful observation of the hosts.In the reported case of introduction of several specimens of Testudo graeca infested by ticks, the hosts were kept in a large private garden with a Mediterranean-type climate and vegetation.After some years of recurrent tick parasitism in the tortoises without new importations and repeated treatments, it was realized that the tick had permanent populations in the garden, and the hosts became infested according to the seasonal activity of the ticks.
An interesting case of tick introduction into mainland Europa are ticks commonly found on snakes, like Amblyomma latum and A. exornatum (both formerly in the genus Aponomma).Th ese ticks feed for a long period on the host, and owing to their small size and preference to feed under host scales, they are commonly unrecognized while importing a host out of its native range.Amblyomma latum is a very common parasite of Python spp., which is becoming increasingly popular as a pet in Europe.Th e only known case of an importation of A. exornatum was noticed on specimens of Varanus niloticus that arrived into Spain (Estrada-Peña (Unpubl.)).Th ese imported ticks founded a permanent population in the terrarium where the lizards live, under suitable conditions of high relative humidity and controlled temperature.
A very peculiar case of tick introduction is an alien in Europe, the brown dog tick, Rhipicephalus sanguineus.While feeding on domestic dogs, this tick is endophilic and is normally restricted to the Mediterranean region, being abundant in kennels, human constructions and private gardens where dogs remain unprotected against tick bites.Because of its endophilic behaviour, this tick may survive independently of prevailing environmental conditions, since human habitations buff er harsh climate.Th erefore, unprotected pets travelling may harbor feeding ticks, and introduce them to uninfested areas which might be far from their native range.Such cases of introduction have been commonly recorded in the United Kingdom and northern European countries (Garben et al. 1980, Sibomana et al. 1986), as well as in Czech Republic (Černý 1985).Although there are as yet no reports of its establishment outdoors, this tick could become established out of its former native range as a consequence of global warming.Aculops gleditsiae (Keifer, 1959).

Figure 7
Figure 7.4.1.Relative importance of the mite families in the alien and native fauna in Europe.Families are presented in a decreasing order based on the number of alien species.Species alien to Europe include cryptogenic species.Only the most important families of native species (> 50 spp.)have been considered.Th e number over each bar indicates the number of species observed per family.

Figure
Figure 7.4.2.Temporal changes in the mean number of records per year of mite species alien to Europe from 1800 to 2009.Th e number over each bar indicates the absolute number of species newly recorded per time period.

Figure 7
Figure 7.4.3.Origin of the mite species alien to Europe.

Figure 7
Figure 7.4.4.Comparative colonization of continental European countries and islands by mite species alien to Europe.Archipelago: 1 Azores 2 Madeira 3 Canary Islands.

Figure 7
Figure 7.4.5.Main European habitats colonized by the established alien species of mites.Th e number over each bar indicates the absolute number of alien dipterans recorded per habitat.Note that a species may have colonized several habitats.

Figure 7 .
Figure 7.4.6.Alien mites and their damage.a Curling and rusting of black locust leaves caused by Aculops allotrichus b Chlorotic and misshapen leaves of Acer negundo caused by Shevtchenkella brevisetosa (left) and uninfested leaves (right) c Leaf rusting of lilac leaves caused by Aceria petanovicae d Aceria petanovicae, dorsal view-SEM photograph e Rusting of Pinus strobus needles caused by Setoptus strobacus f Setoptus strobacus eggs, juveniles and adults between needles of Pinus strobus g Leaf distortion and unopened damaged fl ower buds of chrysanthemum caused by Paraphytoptus chrysanthemi h Deformed fl ower heads of chrysanthemum caused by Paraphytoptus chrysanthemi i Colony of Cecidophyopsis hendersoni on Yucca leaf j Panonychus citri.(a-i Credit: Radmila Petanović; j Credit: Alain Migeon).

Table 7 .4.1.
List and characteristics of the mite species alien to Europe.Status: A: Alien to Europe; C: cryptogenic species.Country codes abbreviations refer to ISO 3166 (see Appendix I).Habitat abbreviations refer to EUNIS (see Appendix II).