measures to prevent importation

Summary

Invasive alien terrestrial flatworms are predators that can disrupt ecosystem functioning by feeding on native soil fauna. In such a way, invasive alien flatworms can also be indirect plant pests by feeding on beneficial species such as earthworms that contribute towards plant productivity. There are 28+ native species of terrestrial flatworm in Europe with more being identified every year due to renewed scientific interest and developments in taxonomy.

However, these native flatworm species are mostly small and innocuous animals. There are 21+ alien terrestrial flatworm species in Europe (includes four species only found in the UK) and some of these are much larger and damaging predators. For example, the invasive alien New Zealand flatworm (Arthurdendyus triangulatus) can reduce earthworm biomass by 20% in pasture leading to a reduction in grass yield of 7%. Arthurdendyus triangulatus is currently restricted to the British Isles and Faroe Islands but another large flatworm species, Obama nungara, is spreading in continental Europe and could have similar impacts to A. triangulatus.

The key pathway for introduction of alien flatworms is plants for planting (nursery stock), especially containerised plants with growing media. The flatworms opportunistically shelter in plant containers and are not associated with a particular plant product. Very few control measures against invasive alien flatworms have been tested. Potentially, the most promising approach is hot water treatment applied as a drench. Flatworms are cryptic, nocturnal species and difficult for plant inspectors to detect. However, they would potentially be an ideal target for the development of environmental DNA detection techniques. Invasive alien flatworms are also spreading elsewhere in the world but no countries have specific phytosanitary treatments targeted at such species.

Brief evaluation of the potential size of the threat posed by alien flatworms

Key points:

 Worldwide, there are 944 described terrestrial flatworm species  Many more species remain to be described  There are 28 (to possibly 43) terrestrial flatworm species native to Europe (EU27)

 There are at least 21 alien flatworm species recorded in Europe (EU27 = 17, 4 only from the UK)

Number of flatworm species or genera alien to Europe

The number of described terrestrial flatworm species (Platyhelminthes, Tricladida, Geoplanidae) is c. 944 in 67 genera (GBIF 2021; Turbellarian Taxonomic Database 2021), which fits with estimates of 800-900 in earlier publications [START_REF] Sluys | Global diversity of land planarians (Platyhelminthes, Tricladida, Terricola): a new indicator-taxon in biodiversity and conservation studies[END_REF][START_REF] Sluys | Invasion of the flatworms[END_REF][START_REF] Sluys | The evolutionary terrestrialization of planarian flatworms (Platyhelminthes, Tricladida, Geoplanidae): a review and research programme[END_REF]Tyler et al. 2006[START_REF] Tyler | World List of turbellarian worms: Acoelomorpha, Catenulida, Rhabditophora[END_REF]. However, this is likely to be a substantial underestimate as these are cryptic soil-dwelling species with most found in biodiversity-rich and under-investigated sub-tropical and tropical forests. The majority of terrestrial flatworm species are found outside of Europe, with hotspots in South America, eastern Australia (incl. Tasmania), New Zealand, South-East Asia and Madagascar [START_REF] Sluys | Land planarians (Platyhelminthes, Tricladida, Terricola) in biodiversity and conservation studies[END_REF].

Of the five subfamilies of Geoplanidae (Bipaliinae, Microplaninae, Geoplaninae, Rhynchodeminae, Eudoxiatopoplaninae) two are native to Europe, namely the Microplaninae and the Rhynchodeminae [START_REF] Álvarez-Presas | Diversity of introduced terrestrial flatworms in the Iberian Peninsula: a cautionary tale[END_REF], although for the latter subfamily its status as endemic is questionable [START_REF] Álvarez-Presas | Hidden diversity in forest soils: Characterization and comparison of terrestrial flatworm's communities in two national parks in Spain[END_REF]. The number of native species in Europe was given as ten (one species undescribed) in the review by [START_REF] Jones | The African and European land planarian faunas, with an identification guide for field workers in Europe[END_REF] (Table 1), who pointed out the paucity of terrestrial flatworm records from Europe due to a cessation of taxonomic studies in the 20 th century. Subsequently, other recent studies have added at least 18 new species leading [START_REF] Mateos | Species richness in the genus Microplana (Platyhelminthes, Tricladida, Microplaninae) in Europe: as yet no asymptote in sight[END_REF] to suggest on the basis of morphological and molecular analyses that there were considerably more microplanid species to be described from Europe. The details of the native flatworms found in EU27 countries are given in Table 1. [START_REF] Álvarez-Presas | Hidden diversity in forest soils: Characterization and comparison of terrestrial flatworm's communities in two national parks in Spain[END_REF] estimate the current number of European microplanids as 43, presumably including unnamed species known only from molecular diagnostics. As planarian taxonomy continues to be resolved, this figure is likely to increase. None of the European flatworm species (nor earthworm species) have had their risk of extinction assessed according the IUCN Red List Categories and Criteria (IUCN 2012) at a global or European level. There are at least 21 alien flatworm species recorded in Europe (Table 2). As with native flatworms, this number is likely to increase as several species have yet to be identified. Land planarians are carnivorous so potentially have an impact on other soil dwelling invertebrates but aside from predation lists developed from observational studies, very little is known about the impact of most species of terrestrial flatworm on prey populations. In contrast to the majority of native European species which are generally small and discrete, most alien species are large animals and it is likely that their impact is high and related to their great size.

However, their impact is not documented, except for A. triangulatus [START_REF] Murchie | The impact of the 'New Zealand flatworm', Arthurdendyus triangulatus, on earthworm populations in the field[END_REF]. Impacts on soil fauna are easy to overlook and it is possible that even small flatworm species could be having a significant predatory impact on some soil fauna species. The basic ecology of both native and alien terrestrial flatworms is poorly known.

1.3 Number of species that are considered to be invasive alien species somewhere in the world [START_REF] Winsor | Terrestrial planarians (Platyhelminthes: Tricladida: Terricola) predaceous on terrestrial gastropods[END_REF] lists c. 30 species (depending on taxonomy) that have been found outside their native range in other parts of the world apart from Europe, although many of these are not considered damaging (selected examples are given in Table 3).

The impact of alien flatworms on plant health as indirect pests and on agriculture

Key points:

 Terrestrial flatworms are predatory and may eat beneficial species such as earthworms  Indirect plant pests reduce plant productivity but do not feed directly on plants  Arthurdendyus triangulatus reduces earthworm biomass by 20% leading to a predicted reduction in grass yield of 7%

 Obama nungara is established in continental Europe and could have a similar impact on earthworms as A. triangulatus

 Terrestrial flatworms may prey on pest slugs or snails and have been introduced

elsewhere for biocontrol purposes but this has led to negative impacts on native species  Flatworm contaminated consignments or products are likely to be rejected by consumers and traders Indirect plant health pests are species which have an impact on crop production, even though they do not feed directly on plants themselves. Terrestrial flatworms are predators of other soil fauna and therefore their impact is mostly evaluated in terms of reducing biodiversity. Mostly this is through direct predation (or potentially competition with native species) but there is also some evidence of potential detrimental effects on vertebrates that inadvertently eat flatworms (Winsor, 1983b). Soil fauna are important components of soil ecosystem functioning, which is of direct benefit to agricultural production. Soil fauna feed on dead plant material and microflora, thus helping in the decomposition process and recycling of nutrients within the soil.

Assessing the impact of flatworms on agricultural production has therefore two stages: first, determining the impact of the predatory flatworms on their soil fauna prey; and second, determining the value of the invertebrate prey to agricultural production.

The New Zealand flatworm, Arthurdendyus triangulatus, is an example of an indirect plant pest because it preys on earthworm species that benefit crop yield, but does not itself feed on plants [START_REF] Murchie | Between two stools: dealing with the problem of the New Zealand flatworm[END_REF][START_REF] Sluys | Invasion of the flatworms[END_REF]). This may have important implications for the overall management of the problem, because as plant health legislation is usually dependent on pest risk assessments of direct economic losses, the impact of the flatworms does not fit easily into current legislative frameworks. In some initial discussions, it was even suggested by legislators that A. triangulatus should be considered a veterinary problem because it fed on animals. This shows that there is not a simple way to address the problem.

Arthurdendyus triangulatus is the most studied terrestrial flatworm in Europe in terms of its negative impacts on agriculture. Several studies have demonstrated a reduction in earthworm biodiversity and densities following introduction of A. triangulatus. The first of these was the study by [START_REF] Blackshaw | The effects of a calcareous seaweed product on earthworm populations in grassland soil[END_REF] in Northern Ireland, where a marked decline in earthworm number and biomass was noted during an earthworm enhancement experiment (1983)(1984)(1985)(1986)(1987), and associated with an increase in numbers of A. triangulatus. Subsequent studies confirmed the capability of A. triangulatus to reduce earthworm populations [START_REF] Blackshaw | Studies on Artioposthia triangulata (Dendy) (Tricladida, Terricola), a predator of earthworms[END_REF][START_REF] Blackshaw | Changes in populations of the predatory flatworm Artioposthia triangulata and its earthworm prey in grassland[END_REF][START_REF] Blackshaw | Artioposthia triangulata (Dendy,1894), a predatory terrestrial planarian and its potential impact on lumbricid earthworms[END_REF]). Although A. triangulatus will prey on all lumbricid earthworm species presented to it [START_REF] Stewart | The Biology of the Terrestrial Planarian Artioposthia triangulata (Dendy, 1894) and its Genetic Variation in Colonized Habitats[END_REF], some earthworm species are more susceptible to flatworm predation than others. There are two reasons for this. The first is to do with the ease by which flatworms can access earthworms, with surface dwelling and verticalburrowing earthworm species more vulnerable to predation than deeper, soil-dwelling species [START_REF] Blackshaw | Changes in populations of the predatory flatworm Artioposthia triangulata and its earthworm prey in grassland[END_REF][START_REF] Blackshaw | Artioposthia triangulata (Dendy,1894), a predatory terrestrial planarian and its potential impact on lumbricid earthworms[END_REF][START_REF] Boag | A further record of the New Zealand flatworm Artioposthia triangulata (Dendy) in England[END_REF][START_REF] Lillico | Studies of the behaviour of Artioposthia triangulata (Platyhelminthes; Tricladida), a predator of earthworms[END_REF]. Second, the capability of earthworm populations to absorb the impact of flatworm predation is dependent on the life history characteristics of the species, with larger, longer-lived and slowreproducing species more vulnerable than smaller fast-reproducing species [START_REF] Murchie | The impact of the 'New Zealand flatworm', Arthurdendyus triangulatus, on earthworm populations in the field[END_REF]. Consequently, anecic earthworm species, in particular Lumbricus terrestris, which have semi-permanent vertical burrows and are slow reproducing, are most at risk from A.

triangulatus predation [START_REF] Blackshaw | Changes in populations of the predatory flatworm Artioposthia triangulata and its earthworm prey in grassland[END_REF][START_REF] Blackshaw | Artioposthia triangulata (Dendy,1894), a predatory terrestrial planarian and its potential impact on lumbricid earthworms[END_REF]Jones et al. 2001). The contribution of individual earthworm species to crop production has not been well studied, but L. terrestris has been termed an 'ecosystem engineer' due to its ability to change soil characteristics and flora [START_REF] Bohlen | Non-native invasive earthworms as agents of change in northern temperate forests[END_REF].

In a 4-year manipulation study, [START_REF] Murchie | The impact of the 'New Zealand flatworm', Arthurdendyus triangulatus, on earthworm populations in the field[END_REF] sought to quantify the impact of A.

triangulatus on earthworm populations in the field. They physically moved flatworms around a naturally-infested grass field site to create plots with different flatworm densities. This allowed them to regress earthworm biomass against flatworm densities. There was an overall negative relationship between flatworm density and earthworm biomass. Taking a fieldobserved flatworm density of 0.8 per m 2 as a baseline [START_REF] Murchie | Invasion of agricultural land by the earthworm predator, Arthurdendyus triangulatus (Dendy)[END_REF], gave a reduction in total earthworm biomass of 20%. However, the majority of this was due to loss of anecic species, which suffered a 74% reduction in biomass. At 1.1 flatworms per m 2 , the anecic earthworm biomass is reduced to zero.

Earthworms are considered beneficial soil organisms in agro-ecosystems and particularly so for permanent grass pasture. Their burrowing creates channels that aerate and drain the soil, whilst their feeding activities help to recycle plant nutrients [START_REF] Edwards | Scientific Opinion on the pest categorisation of Ditylenchus destructor Thorne[END_REF][START_REF] Curry | Grassland Invertebrates. Ecology, influence on soil fertility and effects on plant growth[END_REF]. The loss of earthworm species due to flatworm predation could have a number of negative effects. Lack of earthworm burrowing and collapse of old burrows could impede drainage leading to increased water-logging, greater prevalence of Juncus rushes and exacerbate livestock diseases such as liver fluke (Fasciola hepatica) which rely on wet pasture conditions [START_REF] Alford | Potential problems posed by non-indigenous terrestrial flatworms in the United Kingdom[END_REF]). These issues may become more important with climate change causing increased flooding events. Earthworms feed on dead plant material and lack of earthworms increases thatch formation at the soil surface [START_REF] Clements | The impact of 20 years' absence of earthworms and three levels of N fertiliser on a grassland soil environment[END_REF]. Thatch buildup has been associated with the presence of A. triangulatus [START_REF] Blackshaw | Changes in populations of the predatory flatworm Artioposthia triangulata and its earthworm prey in grassland[END_REF]. Furthermore, a layer of thatch at the soil surface may provide an ideal habitat for flatworms. In a mulch experiment in orchard plots, high densities of A. triangulatus (9.3 m -2 ) were found under a thick layer of thatch [START_REF] Murchie | High densities of 'New Zealand flatworms', Arthurdenyus triangulatus (Dendy), in experimental orchard plots in Northern Ireland and implications for thatch formation[END_REF], leading the authors to consider a 'vicious circle': A. triangulatus feeds on earthworms, lack of earthworms leads to build up of thatch, thatch proves to be an ideal habitat for flatworms.

The role of earthworms in recycling nutrients and their relationship with plant productivity is the major factor when assessing the impact of A. triangulatus predation on agriculture. It is notable that one of the best demonstrations of earthworms benefitting agricultural systems comes from New Zealand, where European earthworm species were introduced to pastures and increased grass yield by up to 29% [START_REF] Stockdill | Effects of introduced earthworms on the productivity of New Zealand pastures[END_REF]). Arthurdendyus triangulatus is not considered a pest in New Zealand agriculture, perhaps due to unfavourable conditions in pastures and differences in earthworm prey availability [START_REF] Fraser | The distribution of lumbricid earthworm communities in relation to flatworms: a comparison between New Zealand and Europe[END_REF], along with natural controlling factors of flatworms in their native habitat. The benefit of earthworms to crop yield was quantified in a meta-analysis of 58 studies [START_REF] Van Groenigen | Earthworms increase plant production: a meta-analysis[END_REF]. Overall, presence of earthworms increased crop yield by 25% and above ground biomass of pasture grasses of 24%. For the main pasture species, ryegrass, the figure was greater at a 34% increase in above ground biomass. [START_REF] Murchie | Earthworms and grassland productivity: impact of the New Zealand flatworm and slurry[END_REF] used these figures to calculate the impact of A.

triangulatus as a reduction in pasture biomass of 6.8%, based on a 20% reduction in earthworm biomass x 34% contribution of earthworms to ryegrass biomass. They do however caution that since the contribution of individual earthworm species is not factored in, the disproportionate impact of A. triangulatus predation on anecic species could lead to greater losses.

For other flatworm species, evidence of impact on agriculture is sparse. For the earthworm predators (e.g. Bipalium spp. and O. nungara), it is possible that they will have a similar impact to A. triangulatus being of a large size and similar ecology. There is some evidence from the US of invasive alien Bipalium spp. having an impact on commercial earthworm production [START_REF] Dindal | Feeding behavior of a terrestrial turbellarian Bipalium adventitium[END_REF][START_REF] Sluys | Invasion of the flatworms[END_REF]). Much will depend on the habitats invaded, whether the flatworms can survive open farmland and the densities achieved. Bipalium kewense and O. nungara are found in the wild in continental Europe but most records are from gardens [START_REF] Justine | Giant worms chez moi! Hammerhead flatworms (Platyhelminthes, Geoplanidae, Bipalium spp., Diversibipalium spp.) in metropolitan France and overseas French territories[END_REF]Justine et al. 2020c). There is no evidence to date of significant invasion of agricultural land.

This may be recorder bias with gardeners more likely to see and report unusual flatworms than farmers, who are often working in machinery remote from the soil. However, it may also reflect the different stages in the invasion process. The majority of early records of A. triangulatus were from gardens [START_REF] Moore | Status and public perception of the 'New Zealand flatworm', Artioposthia triangulata (Dendy)[END_REF]. In Northern Ireland, just 4% of grassland fields (n = 75) were found to have A. triangulatus in 1991; yet by 1998/99, 70% of the same fields contained A. triangulatus [START_REF] Murchie | Invasion of agricultural land by the earthworm predator, Arthurdendyus triangulatus (Dendy)[END_REF]. It was postulated that flatworms were initially moved around by the plant trade but once established in gardens they dispersed naturally to surrounding farmland. Given the high densities of O. nungara in some French gardens (Justine et al. 2020c), invasion of surrounding habitats is a virtual certainty.

For flatworm species that prey on soil invertebrates other than earthworms, it is more difficult to evaluate their impact on agriculture. This is because far less is known about the contributions of these prey species (molluscs, isopods and other soil-dwelling arthropods) to agricultural production. In risk-assessing the flatworm snail predator, P. manokwari, for Europe, Murchie & Beckmann (2020) considered that the main biodiversity risk was to endemic snail species and the main economic risk was to heliciculture (snail farming). Although gastropods undoubtedly play an important role in decomposition processes in natural habitats, there was little evidence of a benefit to agricultural production. Indeed, most references to gastropods in agriculture are as crop pests or vectors of livestock diseases. Flatworm predators of snails, such as P. manokwari, have been found to carry vertebrate parasites (Angiostrongylus spp.), which they have ingested whilst feeding on infected snails [START_REF] Chaisiri | Distribution of the newly invasive New Guinea flatworm Platydemus manokwari (Platyhelminthes: Geoplanidae) in Thailand and its potential role as a paratenic host carrying Angiostrongylus malaysiensis larvae[END_REF].

In many tropical territories including islands in the Pacific, P. manokwari has been intentionally introduced in an attempt to limit the proliferation of the Giant African Snail, Lissachatina fulica, also an invasive alien species. The Giant African Snail eats many crops and clearly corresponds to the definition of a species which has a negative impact on agricultural production [START_REF] Vogler | Achatina fulica (giant African land snail)[END_REF], and thus any species which eats this snail would be considered of positive effect on plant production. However, a recent study concluded that P. manokwari is not an effective biocontrol agent, but has major negative effects on native snail fauna [START_REF] Gerlach | Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina 'rosea' and the flatworm Platydemus manokwari[END_REF]. Since some flatworm species now introduced in Europe are predators of terrestrial molluscs, especially O. nungara, there is a potential danger that professionals or amateur gardeners will voluntarily spread it to limit the proliferation of snails and slugs; the effects of the predator flatworm on snails and slugs would be easily visible, while its effect on earthworms would remain unnoticed. Communication with the public will be essential for avoiding unscheduled initiatives for propagating the flatworms.

The final issue to consider is the effect of invasive flatworms on both local and international horticultural trade [START_REF] Alford | Potential problems posed by non-indigenous terrestrial flatworms in the United Kingdom[END_REF]. The presence of invasive flatworms in products bought from a garden centre or nursery could lead to reputational damage and subsequent loss of customers [START_REF] Boag | The spread and movement of the New Zealand flatworm (Arthurdendyus triangulatus) in Scotland[END_REF]. There is also potential for contamination of foodstuffs. Parakontikia ventrolineata has a tendency to be found on fruit and vegetables within gardens in France and disgusts those wishing to consume the produce. If flatworm contamination is suspected, crossborder shipments are likely to be rejected.

Active pathways of introduction of flatworms into the EU (commodities, conditions

for survival during transport etc.)

Key points:

 Flatworms are associated with trade in containerised plants  They opportunistically shelter in plant containers  They are not associated with a particular plant product  Growing media and plant root balls are a buffered environment  The greatest cause of mortality of flatworms during transit is likely to be desiccation  Egg capsules (cocoons) may be a more robust life-stage than adults

The association of invasive alien flatworms with gardens, nurseries and botanic gardens implies that most species have been introduced into Europe via the plant trade and in particular containerised plants and plants for planting [START_REF] Álvarez-Presas | Diversity of introduced terrestrial flatworms in the Iberian Peninsula: a cautionary tale[END_REF][START_REF] Blackshaw | Artioposthia triangulata (Dendy,1894), a predatory terrestrial planarian and its potential impact on lumbricid earthworms[END_REF]; Sluys 2016). Flatworms can be embedded in the growing media in containers or sometimes within plant material itself. For example, a number of bright yellow flatworms (Fletchamia sp.) were discovered inside Dicksonia antarctica tree ferns imported from Australia, during a plant health inspection of a nursery in the UK [START_REF] Cannon | Invasive, non-native plant pests[END_REF][START_REF] Matthews | Imported tree ferns as a potential source of invasive alien antipodean invertebrates[END_REF]. Paraba multicolor, a Brazilian species was intercepted in imported plants in Germany [START_REF] Kraepelin | Ueber die durch den Schiffsverkehr in Hamburg eingeschleppten Tiere[END_REF]. However, plant health interceptions of flatworms are relatively rare, with most initial findings following establishment in gardens and nurseries. Aside from the example of tree ferns, associations of flatworms with a particular commodity are largely speculative. The flatworms are not transported on a host plant like a phytophagous pest, but rather opportunistically shelter in the suitable habitat (a plant container) and are unintentionally transported and introduced. Arthurdendyus triangulatus was considered to have been unintentionally introduced into Northern Ireland from New Zealand with daffodil bulbs [START_REF] Willis | The occurrence of the land planarian Artioposthia triangulata (Dendy) in Northern Ireland[END_REF], but [START_REF] Blackshaw | Artioposthia triangulata (Dendy,1894), a predatory terrestrial planarian and its potential impact on lumbricid earthworms[END_REF] thought that trade in roses was more likely. Flatworms may be transported in other material. There are reports of flatworms being moved around locally in topsoil, manure and soil on machinery. Flatworms appear to have an affinity with plastic on the soil surface, presumably because it provides a moist, smooth and compressed resting habitat. Flatworms have been moved stuck to the outside of plastic bags containing potting soil and fertiliser (J-L Justine, unpubl.), and on the plastic wrapping surrounding baled silage [START_REF] Boag | The spread and movement of the New Zealand flatworm (Arthurdendyus triangulatus) in Scotland[END_REF]. It is thought that A. triangulatus may have been transported to the Faroe Islands with potatoes from Scotland. In the US, flowers from Mexico were found to contain Parakontikia ventrolineata [START_REF] Sluys | Invasion of the flatworms[END_REF]. Contamination of fruit and vegetables is feasible with flatworms sheltering in plant material but they would be less likely to survive being more susceptible to desiccation during international transit.

Flatworms are soil-dwelling and therefore a plant container with moist growing media represents a protected and buffered environment. Active flatworms lack water-retaining physiology and are susceptible to desiccation. However, it would seem that the conditions necessary to transport live plant material are largely suitable for flatworms. In unfavourable dry conditions, flatworms may aestivate deeper within the soil in mucus lined chambers [START_REF] Winsor | Terrestrial planarians (Platyhelminthes: Tricladida: Terricola) predaceous on terrestrial gastropods[END_REF], although given the size of a plant container, this might be unlikely. The susceptibility of flatworm egg capsules (cocoons) to desiccation is largely unknown and they may be a more resistant life-stage during transit. They would also be smaller and potentially more mechanically robust than the adults. There has been comparatively little research on this.

Flatworms can survive without feeding for several months [START_REF] Baird | Long-term effects of prey-availability, partnering and temperature on overall egg capsule output of 'New Zealand flatworms', Arthurdendyus triangulatus[END_REF], so the availability of prey would not be a limiting factor. As flatworms are not associated with a particular host plant or goods, it is difficult to specify a definitive trade route. Imported plants from both flatworm's native and invaded habitats constitute a risk. This is thus a world-wide problem, given the potential sources of invasive alien flatworms within and outside of Europe.

It is recognised that plants for planting (nursery stock) present a greater risk of pest introduction than other commodities, due to the increased likelihood of pest survival on plant and soil material, the subsequent use of the plants in the wider environment and the diversity of plants traded from many differing origins (EPPO 2012).

Any method available that is or could be applied during transport to prevent introductions

Key points:

 Potential treatments must balance flatworm mortality against phytotoxicity  Control by temperature manipulation would depend on the flatworm species  Fumigation would be a possible means of flatworm eradication in-transit but has not been tested. Pesticides used against nematodes would likely not be active against flatworms.

The consensus is that most alien flatworms have entered Europe through trade in containerised plants. The flatworms were sheltering in plant pots or in crevices in the plants themselves. The problem in treating the flatworms in-transit is to find measures that would kill them but not harm the living plants. As the number plant species involved in trade is large and diverse, this would need to be considered on a case-by-case basis looking the requirements of the plants and the flatworm species concerned. Temperature manipulation, for example transit in cold storage may kill tropical flatworm species such as Platydemus manokwari, which are susceptible to lower temperatures. For P.

manokwari temperatures below 18°C for 14 d resulted in increased mortality in the laboratory [START_REF] Gerlach | Predation by invasive Platydemus manokwari flatworms: a laboratory study[END_REF]. However, the opposite would be true for a cold-hardy species such as Arthurdendyus triangulatus from New Zealand, which would survive well at lower temperatures, e.g. 5°C [START_REF] Blackshaw | The effect of starvation on size and survival of the terrestrial planarian Artioposthia triangulata (Dendy) (Tricladida, Terricola)[END_REF]. Conversely, temperatures above 20°C would be detrimental to A. triangulatus survival, but may not be practical for shipping plants due to increased need for watering and husbandry.

Fumigation is used as a phytosanitary measure to treat plants and soil. Previously, the most common fumigant used was methyl bromide but this was removed from use in the EU in 2010 due to environmental (ozone depletion) and human health concerns, although it may still be used in countries exporting to the EU, and for restricted plant health purposes in other countries including the US, China, India, Australia and New Zealand [START_REF] Cox | Quarantine and pre-shipment uses of methyl bromide 2013-2016 and the potential for its replacement[END_REF][START_REF] Eschen | International variation in phytosanitary legislation and regulations governing importation of plants for planting[END_REF].

Alternative fumigants have been trialled for plant health purposes and these include sulfuryl fluoride, phosphine and ethanedinitrile. We are not aware of any studies testing the effectiveness of chemical fumigants against flatworms. However, as fumigants are used for phytosanitary control of other soil-dwelling pests (e.g. nematodes) they may be a possibility for flatworm eradication providing phytotoxic effects were kept to a minimum and there are no human health concerns. However, the specific chemicals used would need to be trialled. In general, pesticides and medicines targeted against nematodes are not effective against flatworms.

Other possibilities for in-transit treatment are controlled atmosphere treatment and irradiation.

Controlled atmosphere treatment involves lowering oxygen levels by pumping in CO2, nitrogen or other gases into a sealed container. This is mainly used for pest control on delicate artefacts but has shown potential for control of insect pests on living plants [START_REF] Held | Modified atmosphere treatments as a potential disinfestation technique for arthropod pests in greenhouses[END_REF]). There have been no studies on whether this would be a feasible option for flatworm control.

Irradiation is an established phytosanitary procedure for fresh fruits and vegetables in the US, Australia and New Zealand [START_REF] Hallman | Phytosanitary irradiation[END_REF]. It is doubtful whether it would be useful on live plants due to the potential for damage to the product.

Any method available that could be applied at inspection points to detect flatworms in imported containerised plants and plants-for-planting

Key points:

 Current methods of detection are visual inspection and destructive sampling  Flooding plant containers may expel adult flatworms (but not egg capsules)

 eDNA technology has great promise for detecting flatworms in plant containers

Due to their cryptic nature, detection of flatworms is problematic. The presence of mucus or slime on plant material or underneath plant pots may be indicative of flatworm presence but further examination would be necessary to confirm as native slugs and snails would also leave slime trails. Visual inspection is unlikely to be effective on its own. A proportion of plants would need to be destructively sampled by uprooting, hand-sorting and examination of rootballs and growing media.

It has been suggested that submerging plant pots in water overnight will force flatworms out from the growing media (B. Boag, pers. comm.) and this could be used by nurseries to check imported stock for flatworms. As far as we are aware this has not been trialled experimentally.

Flatworms can also be expelled from soil using the chemical methods (e.g. a mustard solution)

for sampling earthworms [START_REF] Murchie | The impact of the 'New Zealand flatworm', Arthurdendyus triangulatus, on earthworm populations in the field[END_REF]. It is possible that adult flatworms could be expelled from growing media in the same way by applying a drench to the plant containers.

However, these techniques will not work for egg capsules (cocoons) embedded in the soil as they are immobile. Also, the impact of submerging containers and drenches would need to be assessed in terms of their impact on the plant product. It may be that this would also constitute destructive sampling for a proportion of a consignment.

A possible novel alternative is to use environmental DNA (eDNA) techniques. As flatworms reside within the growing media in containers, they will shed mucus and faeces. Passing water through the growing media would enable the run-off to be screened for flatworm eDNA signatures using diagnostic PCR. This would have the advantage of being a minimally invasive technique and, depending on the sensitivity, could process a large number of samples by pooling the initial washings. Environmental DNA techniques are widely used for monitoring aquatic species, including invasive alien species [START_REF] Darling | From molecules to management: Adopting DNA-based methods for monitoring biological invasions in aquatic environments[END_REF][START_REF] Dejean | Improved detection of an alien invasive species through environmental DNA barcoding: the example of the American bullfrog Lithobates catesbeianus[END_REF][START_REF] Larson | From eDNA to citizen science: emerging tools for the early detection of invasive species[END_REF]. They have also been used to detect plant pathogens (Phytophthora spp.) in water and soil samples [START_REF] Catala | The use of genus-specific amplicon pyrosequencing to assess phytophthora species diversity using eDNA from soil and water in Northern Spain[END_REF]. The technique has been mooted as a portal inspection tool for marine invasive alien species [START_REF] Borrell | DNA in a bottle -Rapid metabarcoding survey for early alerts of invasive species in ports[END_REF][START_REF] Zaiko | Metabarcoding approach for the ballast water surveillance -An advantageous solution or an awkward challenge?[END_REF] and has recently been considered for plant health applications such as detecting invasive forest insects by using water sprays to collect eDNA from trees [START_REF] Valentin | Moving eDNA surveys onto land: Strategies for active eDNA aggregation to detect invasive forest insects[END_REF]. As flatworms produce mucus and are in an enclosed space within growing media, it seems that they would be an ideal target for eDNA detection following a wash through with water. However, the technique would need to be developed and trialled for both known and potentially unknown flatworm species.

6. Any method that could be used to minimise the survival of flatworms on such plants (e.g. heat treatment)

Key points:

 There are no approved pesticides for flatworm control and few studies on this topic  Hot water immersion is a recognised phytosanitary procedure and the most likely means of disinfesting containerised plants If necessary, pesticides can be applied post-import and post-inspection to eradicate plant health pests. However, there are very few studies on pesticidal control of invasive flatworms.

Grassland pesticides were largely ineffective against Arthurdendyus triangulatus, with only the now-withdrawn organochlorine insecticide, gamma HCH, having an effect [START_REF] Blackshaw | Control options for the New Zealand flatworm[END_REF].

The slug parasitic nematode (Phasmarhabditis hermaphrodita) was also not effective against A. triangulatus [START_REF] Rae | Susceptibility of indigenous UK earthworms and an invasive pest flatworm to the slug parasitic nematode Phasmarhabditis hermaphrodita[END_REF]. It is possible that some of the drugs used to treat parasitic flatworms in veterinary or human medicine, such as praziquantel, could be active against freeliving flatworms but this has not been tested. Most of these drugs are not approved for control of agricultural pests but there are a few examples of active ingredients used in both crop protection and endoparasite control, e.g. abamectin (although, it is not active against flukes and hence unlikely to be active against terrestrial flatworms).

Flatworms are sensitive to temperature. Hot water immersion is a recognised phytosanitary measure for control of nematodes and other pests and pathogens. For example, flower bulbs are immersed in water baths at temperatures above 40°C for several hours to eradicate quarantine nematode species such as Ditylenchus dipsaci and Ditylenchus destructor (EFSA PLH Panel 2014; [START_REF] Qiu | Evaluation of hot water treatments for management of Ditylenchus dipsaci and fungi in daffodil bulbs[END_REF]. Hot-water treatment has been suggested as a means to kill invasive flatworms in plant containers [START_REF] Blackshaw | Control options for the New Zealand flatworm[END_REF][START_REF] Sugiura | Hot water tolerance of soil animals: utility of hot water immersion in preventing invasions of alien soil animals[END_REF]. Immersion of A.

triangulatus in water at 30°C for 20 minutes, killed adults within 24 h, while immersion for only 5 minutes at 34°C killed adult flatworms within 1 h (Murchie & Moore 1998). For tropical flatworm species, the temperatures used will need to be higher. However, exposure to temperatures above 43°C resulted in 100% mortality of P. manokwari after 5 minutes [START_REF] Sugiura | Hot water tolerance of soil animals: utility of hot water immersion in preventing invasions of alien soil animals[END_REF]. This would still be within the range used for nematode control, although the effects on plants would need to be evaluated, as would the ability of hot water to penetrate the growing media. [START_REF] Hendrix | Pandora's Box contained bait: The global problem of introduced earthworms[END_REF]) and predatory flatworms have been mentioned, albeit cursorily, as potential biocontrol agents. However, the finding of P.

manokwari, a snail predator, in Florida, USA has significantly raised the profile of invasive alien flatworms in North America with much media interest [START_REF] Justine | The invasive land planarian Platydemus manokwari (Platyhelminthes, Geoplanidae): records from six new localities, including the first in the USA[END_REF][START_REF] Sluys | Invasion of the flatworms[END_REF].

Despite this, and clear recognition of the threat to biodiversity, P. manokwari is not a regulated species within Florida probably because it is so well established, being found now in 40 counties and other US states. This means that there are no restrictions in moving the species around the state, although for inter-state movement a permit would be required, if say flatworm infestation of soil was suspected (Florida Fish and Wildlife Conservation Commission 2021) but there seems to be no specific monitoring or controls in place. At the federal level in the USA, pests and harmful species are overseen by the Animal and Plant Health Inspection Service (APHIS), which is part of the U.S. Department of Agriculture. Although there is no specific mention of invasive alien flatworms in the Code of Federal Regulations, as predatory species, invasive alien flatworms would be governed by general regulations covering biological control agents [START_REF] Sluys | Invasion of the flatworms[END_REF].

One of the key differences that made the EU vulnerable to invasive alien flatworm incursion is that plants for planting were previously allowed to be imported in sufficient growing media to sustain them in transit, whereas other countries had stricter biosecurity approaches to growing media. Depending on the size of plants, substantial quantities of soil may have been involved, leading [START_REF] Eschen | International variation in phytosanitary legislation and regulations governing importation of plants for planting[END_REF] to comment that 'in effect an entire ecosystem is being transplanted'. However, the current EU Commission Implementing Regulation (EU)

2019/2072 came into force in 2019 and stipulates the special requirements for growing medium attached to plants to sustain them. The special requirements (Annex VII) are summarised as follows:

a-i) the growing medium was free from soil and had not previously been used to grow plants, a-ii) or was composed of peat or coconut fibre, a-iii) or was subjected to fumigation or heat treatment, a-iv) or was subjected to effective systems approach to ensure freedom from pests, and stored in appropriate conditions to keep it free from quarantine pests, and since planting, b-i) physical or hygiene measures have been taken to ensure freedom from Union quarantine pests b-ii) or within two weeks prior to export, the soil has been completely washed off and plants may be replanted.

Following from Brexit, DEFRA (UK) have produced guidelines for UK exporters to the EU27 (DEFRA 2020). This provides practical measures to be taken to meet the requirements above.

For b-i) this includes physical isolation from soil and other sources of contamination and specifies that the plants be maintained on raised benches or concrete and that pots with drainage holes should on a saucer or impermeable layer. Such approaches have been recommended to prevent contamination with invasive alien flatworms (EPPO 2001a,b). If the current procedures are followed precisely, this should minimise the likelihood of contamination with invasive alien flatworms but much depends on compliance, inspection and policing of these phytosanitary requirements.

Australia and New Zealand generally have the strictest phytosanitary regulations and consignments with soil are not permitted. It is preferred that plants are imported bare-rooted or, if necessary, in inert material to protect them during shipping (Australian Goverment 2021a;

Australian Goverment 2021b; Biosecurity New Zealand 2012). Such measures clearly restrict the variety and the quantities of plants that can be imported and there is a cost to trade and for implementing biosecurity protocols. In the USA, importation of plants for planting is regulated under the Plant Protection Act by APHIS (Code of Federal Regulations, Part 319, Sub-part H

  [START_REF] Boag | The spread and movement of the New Zealand flatworm (Arthurdendyus triangulatus) in Scotland[END_REF] found A. triangulatus in a nursery in New Zealand that exported plants to Scotland and considered this a potential pathway. The recent finding of Artioposthia exulans in the UK was discussed by[START_REF] Jones | Specimens of a New Zealand terrestrial planarian, Artioposthia exulans (Dendy, 1901) (Platyhelminthes: Geoplanidae) from Cornwall, UK[END_REF] who considered that the flatworm may have been transported from New Zealand in leaf structures of Phormium spp. (New Zealand flax). Bipalium kewense and P. manokwari have both been found in Europe in hothouses, where they have been introduced with exotic plants. This has been happening for a while. The name kewense comes from Kew Gardens in London, where B. kewense was first found and described in 1878. More recently, P. manokwari has been found in a hothouse in Caen, France, representing the sole record of this species in Europe(Justine et al. 2014b). However, it is unknown with what plants or shipments that flatworms were transited.

Table 1 .

 1 Native European terrestrial flatworm species, their distribution and key recent references. Please note, this effectively corresponds to an EU27 species list. al. 2016

	Microplana nervosa	Spain	Mateos et al. 2017
	Sluys et al., 2017
	Microplana pereraca	Azores	Jones 1998
	Marcus & Marcus, 1959
	Microplana plurioculata	Spain	Sluys et al. 2016
	Sluys et al., 2016
	Microplana polyposis	France	Sluys et al. 2016
	Sluys et al., 2016
	Microplana pyrenaica	France, Portugal	Jones 1998
	(Graff, 1893)

Table 1 .

 1 Native European terrestrial flatworm species, their distribution and key recent references (continued).

	Species	European distribution	References
	Microplana robusta	Spain	Sluys et al. 2016; Vila-Farré
	Vila-Farré & Sluys, 2011		et al. 2011
	Microplana scharffi	Belgium, Ireland, Madeira,	Jones 1998
	(Graff, 1899)	Monaco, European
		Turkey, UK.
	Microplana sparsa	Portugal	Mateos et al. 2017
	Sluys et al., 2017
	Microplana terrestris	Europe-wide	Jones 1998
	(Müller OF, 1773)
	Rhynchodemus howesi	Pyrenees	Jones 1998; Minelli 1977;
	Scharff, 1900		Sluys et al. 2016
	Rhynchodemus	Austria, Azores, Belgium,	Jones 1998
	sylvaticus*	Bulgaria, Czech Republic,
	(Leidy, 1851)	Ireland, France, Germany,
		Italy, Netherlands,
		Poland, Slovakia,
	*possibly introduced	Sweden, UK

1.2 Number of alien species already introduced in Europe, with and without recorded impacts

The number of records of alien species introduced to Europe has increased in recent years due to greater awareness of invasive flatworms, citizen science approaches and increased taxonomic capability, often based on molecular techniques. Some of this interest has been driven by the potential economic impact of A. triangulatus in the UK and Ireland. Nevertheless, there remains significant gaps in our knowledge of flatworm distribution in Europe. Most recent work has been conducted in the UK, France, Spain and the Netherlands.

Table 2 .

 2 This figure has undoubtedly increased in the intervening years since this paper was published with the renewed interest in invasive alien flatworms and advances in taxonomy. It is of note that several European Terrestrial flatworms alien to Europe, their distribution, impact and key recent references. This includes four species that have only been recorded in Europe in the UK (marked with an asterisk).

	Microplana

species have been found in the USA, demonstrating the capacity of these organisms to be transported to other countries. It is presumed that these largely historical introductions were with shipments of European plants and soil to America and before current phytosanitary precautions.

Table 2 .

 2 Terrestrial flatworms alien to Europe, their distribution, impact and key recent references (continued)

	Species	European distribution	Native to	Impact	References
	Diversibipalium	France, Switzerland, Italy	Japan	Predator of invertebrates. Limited	Justine et al. 2018; Mazza et al.
	multilineatum			distribution.	2016
	(Makino & Shirasawa,
	1983)
	Diversibipalium sp.	France	Asia	Limited distribution but high	Justine et al. 2018
	"black"	Italy (J-L Justine unpubl.)		numbers reported in a field in Italy
				(J-L Justine unpubl.)
	Caenoplana variegata	Netherlands, UK, Spain,	Australia	Predator of arthropods (woodlice,	Álvarez-Presas et al. 2014; de
	(Fletcher & Hamilton,	France, Greece (Crete)		insects, myriapods, spiders),	Waart 2016; Jones et al. 2020;
	1888)			scavenger	Justine et al. 2020b;
	[syn. Caenoplana bicolor]				Vardinoyannis & Alexandrakis
					2019
	Caenoplana coerulea	UK (hothouse), France, Spain	Australia	Predator of arthropods. Limited	Álvarez-Presas et al. 2014;
	Moseley, 1877			distribution.	Breugelmans et al. 2012; Jones
					1998; Jones 2005
	Caenoplana decolorata	Spain, France	Australia	Predator of invertebrates. Limited	Justine et al. 2020b; Mateos et
	Mateos et al., 2020			distribution.	al. 2020
	Dolichoplana striata	Ireland (hothouse), Jersey,	Sri Lanka or	Earthworm predator. Some	Álvarez-Presas et al. 2014;
	Moseley, 1877	Germany, UK, Spain, France	Indonesia	evidence of impact on earthworm	Anderson 1986; Jones 1998;
	[syn. Dolichoplana feildeni]	(hothouse) (J-L Justine unpubl.)		beds.	Winsor et al. 2004
	Kontikia andersoni	UK, Ireland	Indo-Pacific/?New	Unknown	Anderson 1986; Jones 1998;
	Jones, 1981		Zealand		Winsor et al. 2004
	Kontikia bulbosa	Portugal (Madeira) Spain	Unknown	Unknown	Jones 1998; Winsor et al. 2004
	Sluys, 1983	(Canary Islands)
	*Australopacifica atrata	UK	Australia	Scavenger	Jones 2019
	(Steel, 1897)

Table 2 .

 2 Terrestrial flatworms alien to Europe, their distribution, impact and key recent references (continued)

	Species	European distribution	Native to	Impact	References
	*Parakontikia coxii	UK	Australia	Limited distribution. No evidence	Boag & Yeates 2001;
	(Fletcher & Hamilton,			of impact stated in the literature.	Jones 1998
	1888)
	[syn. Australopacifica
	coxii]
	Parakontikia	UK, France, Spain, Netherlands	Australia	Predator of	Álvarez-Presas et al. 2014;
	ventrolineata			invertebrates/scavenger. A pest	de Waart 2016; Jones
	(Dendy, 1892)			in gardens because it dwells on	1998; Jones et al. 1998;
	[syn. Kontikia			fruits and vegetables.	Justine et al. 2014a
	ventrolineata]
	Marionfyfea adventor	UK, Netherlands, France	?New Zealand	Limited distribution. No evidence	Jones & Sluys 2016
	Jones & Sluys, 2016			of impact stated in the literature.
	Rhynchodemus hallezi	UK hothouse (doubtful)	Philippines	Unknown	Jones 1998
	Graff, 1899
	Obama nungara	Guernsey, Italy, France, Spain, UK	Argentina, Brazil Polyphagous predator of	Justine et al. 2020c; Soors
	Carbayo et al., 2016			invertebrates, including	et al. 2019; Lago-Barcia et
		Austria (J-L Justine, unpubl)		earthworms and snails	al., 2015
		Germany (J-L Justine, unpubl.)
		Switzerland (AK Murchie, unpubl.)
	Platydemus manokwari	France (hothouse). Never found in the	New Guinea	Predator of snails. Serious	Justine et al. 2014b;
	Beauchamp, 1963	wild in Europe.		impact on endemic snails in	Justine et al. 2015
				Pacific islands.

Table 3 .

 3 Selected terrestrial flatworm species that have invaded other (non-European) parts of the world (key reference[START_REF] Winsor | Terrestrial planarians (Platyhelminthes: Tricladida: Terricola) predaceous on terrestrial gastropods[END_REF]

	Species	Country	Native to	Impact	References
	Bipalium adventitium	USA, Canada	Asia	Predator of earthworms. Widespread	Fiore et al. 2004; Justine et
	Hyman, 1943			distribution. Pest of commercial	al. 2019; Sluys 2016
				earthworm beds.
	Bipalium kewense	Worldwide, including EU27	Vietnam	Predator of earthworms. Widespread	Justine et al. 2018; Winsor
	Moseley, 1878	(Table 2)		distribution.	1983a
	Bipalium	USA	Asia	Predator of earthworms	Sluys 2016
	pennsylvanicum
	Ogren, 1987
	Bipalium vagum	Many tropical countries, including	Asia	Predator of molluscs	Ducey et al. 2007; Justine
	Jones & Sterrer, 2005	many Asian countries and			et al. 2018; Sluys 2016
		Southern USA.
		Antilles Islands (Guadeloupe,
		Martinique, Saint Martin, Saint
		Barthélemy); French Guiana; La
		Réunion.
	Dolichoplana striata	USA. Many tropical countries.	lndo-Malay	Predator of earthworms. Pest of	Sluys 2016; Winsor et al.
	Moseley, 1877		region	commercial earthworm beds.	2004
	Parakontikia	USA	Australia	Generalist predator attacking molluscs	Sluys 2016; Winsor et al.
	ventrolineata			and isopods, scavenger	2004
	(Dendy, 1892)
	Platydemus manokwari	Many tropical countries, including	New Guinea	Predator of molluscs. Impact on	Justine et al. 2014b;
	Beauchamp, 1963	Southern USA. Antilles Islands		endemic species (Gerlach et al. 2020)	Justine & Winsor 2020;
		(Guadeloupe, Martinique, Porto			Justine et al. 2015
		Rico, and others). Found in a
		hothouse in France (Table 2).
	Amaga expatria	Bermuda, Antilles (Guadeloupe,	Continental	Predator of both earthworms and	Jones & Sterrer 2005;
	Jones & Sterrer, 2005	Martinique)	South America,	terrestrial molluscs. Possible impact on	Justine et al. 2020a
			precise country	endemic species.
			unknown

Experiences and methods applied outside the EU (regarding preventing introductions, detection and control treatments), particularly in Australia, New Zealand and North America -noting effectiveness and costs if available

  Justine et al. (2014b) suggested that a hot-water drench may be a more practical method of control than immersion for containerised plants. This was based on the work of[START_REF] Tsang | A hot water drenching system for disinfesting roots and media of potted plants of the burrowing nematodes[END_REF] who developed a hot water drenching system to disinfest containerised plants of nematodes. There has been little work on the effects of hot water treatment on flatworm egg capsules. Some preliminary studies suggests that they are as susceptible to heat treatment as adults (A.K.Murchie, unpubl.). Australian or New Zealand legislation. For Australia and New Zealand, this is unsurprising as these countries have not experienced the same problems as Europe and have a more diverse native flatworm fauna that has acted as a source of invasive alien species rather than a recipient. In Australia and New Zealand, terrestrial flatworms have not achieved the same pest status compared to Europe. Where there are alien species (e.g. Platydemus manokwari in Australia, Australoplana sanguinea alba in New Zealand) their impact is not reported to be problematic, perhaps due to the presence of natural regulatory factors such as indigenous predators, competitors or prey resistance.North America is similar to Europe in having smaller native flatworm species, and fewer species, than those found in Australasia, South East Asia and South America (see map in Sluys 1998), so large invasive alien species are notable. However until recently, invasive alien flatworms, mainly Bipalium spp.[START_REF] Ducey | Natural history observations on Bipalium cf. vagum Jones and Sterrer (Platyhelminthes: Tricladida), a terrestrial broadhead planarian new to North America[END_REF][START_REF] Fiore | Tracking and predation on earthworms by the invasive terrestrial planarian Bipalium adventitium (Tricladida, Platyhelminthes)[END_REF], have remained largely of scientific interest rather than provoking widespread concern. This may be because B.

	7. Key points:
	 There are no specific phytosanitary measures applied elsewhere in the world against
	terrestrial flatworms
	 Australia, New Zealand and North America only permit plants for planting to be
	imported with bare roots or in inert growing media
	 The EU allows plants for planting to be imported with sufficient growing media to
	maintain them in transit subject to special requirements to ensure freedom from pests
	We found no phytosanitary measures related specifically to invasive alien flatworms in North
	American,

kewense has been established in North America since 1891

(Winsor 1983a)

, representing the 'old' introduced species as categorised by

Justine et al. (2014b)

. Somewhat ironically, in North America invasion by European earthworm species such as Lumbricus terrestris, a species severely affected by A. triangulatus predation in Europe, has garnered much attention due to their effects on native habitats

This note has been drafted by IUCN within the framework of the contract No 07.0202/2020/834681/SER/ENV

-Plants for Planting). Similar to Australia and New Zealand, plants growing in soil are not permitted, unless from Canada, but some other growing media may be allowed as listed in the Plants for Planting Manual (USDA 2017). Canada also does not permit plants rooted in soil with the exception of those from continental USA (Government of Canada 2015).

Twelve species of terrestrial flatworms have been introduced into Australia / Australian territories but these are likely historic introductions that pre-date current phytosanitary arrangements (L. Winsor, pers. comm.). Australia and New Zealand operate a 'white list' approach, i.e. only permitting commodities that have been assessed as safe, compared to a 'black list' approach in the EU, which targets specific pests and pathogens [START_REF] Eschen | International variation in phytosanitary legislation and regulations governing importation of plants for planting[END_REF].

So although Australia and New Zealand do not specifically legislate against invasive alien flatworms, it would seem that their strict plant health biosecurity, in particular preventing the import of plants rooted in growing media, largely prevents the importation of invasive alien flatworms by acting on their primary pathway of introduction. Some countries, for example Denmark, Sweden, Norway and Iceland, list invasive alien flatworms as quarantine pests [START_REF] Boag | The potential impact of the New Zealand flatworm, a predator of earthworms, in western Europe[END_REF][START_REF] Cannon | A review of the status of the New Zealand flatworm in the UK[END_REF][START_REF] Schrader | Plant quarantine as a measure against invasive alien species: the framework of the International Plant Protection Convention and the plant health regulations in the European Union[END_REF]. Recent local regulations in the French territories in the Antilles have also sought to address the problem of invasive alien flatworm species. The French overseas departments can issue local regulations concerning the environment. It is noteworthy that Guadeloupe, Martinique and Saint Martin have very recently (2020) added several species of invasive alien flatworms on the list of species forbidden for "introduction into the territory, including transit under customs supervision, introduction into the natural environment, possession, transport, peddling, use, exchange, offering for sale, sale or purchase of live specimens" (Anonymous 2020a; Anonymous 2020b; Anonymous 2020c).