Candidula intersecta (wrinkled dune snail)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Candidula intersecta Poiret
Preferred Common Name
- wrinkled dune snail
Other Scientific Names
- Helix carcusiaca Mabille
- Helix deferiana Bourguignat in Locard
- Helix intersecta Poiret
- Helix paladilhi Bourguignat
International Common Names
- English: wrinkled snail
Local Common Names
- Netherlands: grofgeribde grasslak
Summary of InvasivenessTop of page
C. intersecta can be invasive in its countries of origin and is considered an agricultural pest in Europe where it can feed on cereal and horticultural crops (some pome and stone fruit) and is responsible for yield losses. Even if its economic and environmental impact has not been determined, it has the potential to cause damage in the USA, New Zealand and Australia, where it is listed as an “A pest” of quarantine concern in the Plant Quarantine Act 1997.
Meissner et al. (2009) have identified several pathways for the movement and introduction of several species of Candidula, including C. intersecta. These species can hitchhike onto containers, limestone, marble, quarry product, stones, terracotta (and other) tiles, farming machinery, cut flowers and plants.
C. intersecta has been intercepted in 2007 at port of entry in the USA on containers. Hitchcox (2007) reports interceptions on cargo containers from Italy, Colombia, and Chile. Candidula infestations have also been found near port areas in Oregon and Washington state. A report from the Oregon Department of Agriculture (2008) states that C. intersecta was detected for the first time in Douglas County, at a site much further inland than any previous surveys, indicating the species is being moved domestically. It was concluded that eradication is not an option anymore (ODA, 2008). However, no direct impacts on agriculture, nor economic damage have been reported.
Populations of several land snail species have already become established at several US seaports. They fasten on containers in rail yards and can be transported by rail to new destinations where they escape into the environment and impact on local crops.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Pulmonata
- Order: Stylommatophora
- Suborder: Sigmurethra
- Unknown: Helicoidea
- Family: Hygromiidae
- Genus: Candidula
- Species: Candidula intersecta
Notes on Taxonomy and NomenclatureTop of page
The three western European Candidula species, C. gigaxii (Pfeiffer, 1848), C. intersecta (Poiret, 1801) and C. unifasciata (Poiret, 1801) have frequently been confused amongst each other and with other species such as Trochoidea geyeri (Gittenberger, 1993).
Germain (1930) listed Helix paladilh[e]i with Candidula rugosiuscula. This decision is not supported by the original description in Bourguignat’s collection and might belong to other species (one of which is T. geyeri). The other three specimens labelled under Helix carcusiaca could be C. intersecta specimens with an exceptionally prominent apertural rib. Note that Germain (1930) considered H. carcusiaca to be a synonym of H. ramburi (= Candidula gigaxii) (Gittenberger, 1993).
DescriptionTop of page
C. intersecta has a small to medium shell with 5 to 6 whorls (up to 14 mm), sub-globose to turbinate, rounded domed spire, tightly coiled, solid with descending, ovate-lunate aperture and wide umbilicus. The lower lip is reflected. Sculpture of coarse radial wrinkles and lines present. The colour is buff to light brown with dark brown to black irregular blotches (Smith and Kershaw, 1979). The description from Shea (2007) reports a narrow umbilicus with rounded whorls in adults, moderately impressed sutures, thickened ring inside aperture, sculpture of radial growth line. Shell is yellowish with spirally arranged brown broken bands and flammulations and cream radial streaks.
DistributionTop of page
C. intersecta originates from Europe where it is found in Portugal, Spain, Italy, the United Kingdom (including the Isle of Man, Hebrides, the Orkney Islands, and the Shetlands), France, Belgium, the Netherlands, and Ireland. It has also been reported in Holstein (northernmost state of Germany), Denmark and on the island of Öland.
The species is mostly found in the south central plain in Ireland and confined to the coast in northern parts. In Northern Ireland it is present only sparingly on dune grassland or other calcareous soils near the coast (Anderson, 1996).
It has been introduced into South America, USA (Washington State and Oregon), Australia (South Australia, Victoria and Tasmania) and New Zealand.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 10 Jan 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Denmark||Present||East Denmark and Island of Oland|
|Germany||Present||Native||Present in Holstein|
|Spain||Present, Widespread||Native||In northwest Spain|
|United Kingdom||Present, Widespread||Introduced|
|United States||Present||Present based on regional distribution.|
|-Oregon||Present, Few occurrences||2014||Introduced||2000||First reported by Frest and Johannes (2000)|
|-Washington||Present||Introduced||Original citation: Gasa ELa (2008)|
|Australia||Present||Present based on regional distribution.|
|-Tasmania||Present||Introduced||Found in Eagle Neck|
|-Victoria||Present||Introduced||Found in Port Fairy|
|New Zealand||Present, Widespread||Introduced||Collected in Maraetotara Gorge ScR and Maraetotara ScR|
History of Introduction and SpreadTop of page
Many European snail species in the family Helicidae have been deliberately introduced and released to many parts of the world for development and harvest as “escargot” (Cowie and Robinson, 2003). Other species in the related families Hygromiidae and Cochlicellidae have been introduced inadvertently, in or on shipping containers or via the export of roof terracotta tiles (Robinson, 1999). Most of these species are European in origin with Italy (30%) and Spain (7%) accounting for many of the interceptions (Robinson, 1999). The same author listed 50 hygromiid species intercepted by US quarantine officials in the period 1993-98, including C. intersecta (Cowie, 2001).
Meissner et al. (2009) report that in November 2007, four species of molluscs were detected on a single shipment of ceramic tiles from Spain at the port of San Juan, Puerto Rico (CBP, 2007). Tiles contain calcium carbonate that the snails use for building their shells. The cool, dark, and humid conditions in ocean transport allow large numbers of hitchhikers to survive.
C. intersecta is frequently found on imported cargo entering the USA, from countries including Italy, Colombia and Chile (AQAS, 2007; Hitchcox, 2014). In 2006 and 2007, large populations of C. intersecta were found in the environment at several port sites in two Oregon counties. Although the date of introduction cannot be determined, historical evidence suggests the species was first introduced into Oregon prior to 1985 (Hitchcox, 2014). The initial record of C. intersecta in Oregon was reported from a biological inventory study at Sisters Rocks State Park (Frest and Johannes, 2000).
IntroductionsTop of page
Risk of IntroductionTop of page
Land snails are excellent hitchhikers. They can climb up on sea containers and machinery and spread to new destinations and can be transported both short and long distances. The risk of introduction and spread increases with trans-shipment: transhipped containers enter a country through one port, and are unloaded for various periods of time before they are loaded again onto a different vessel and exit for their final destination. Hitchhikers can leave the unloaded containers and spread in the vicinity via port machinery or vehicles. As not all ports record departing, arriving and transhipped containers in separate categories, it is difficult to estimate the percentage of containers to screen for the presence of hitchhikers (Cowie and Robinson, 2003; Meissner et al., 2009).
Land snails including C. intersecta also have the potential to enter via imported cut flowers and plants.
HabitatTop of page
C. intersecta is a temperate species of European origin (Godan, 1983; Hitchcox, 2007). It favours limestone areas and mild coastal climates. This species of land snail can invade and naturalize in a range of environments including cooler maritime climates (e.g., Ireland, UK, Tasmania and New Zealand) and dry, open and exposed habitats. C. intersecta can aestivate during long dry periods and is well adapted to drier climates such as the ones found in Southern Australia (Barker, 1999; 2002).
Habitat ListTop of page
|Terrestrial||Managed||Cultivated / agricultural land||Present, no further details||Harmful (pest or invasive)|
|Terrestrial||Managed||Managed grasslands (grazing systems)||Present, no further details||Harmful (pest or invasive)|
|Terrestrial||Managed||Managed grasslands (grazing systems)||Present, no further details||Natural|
|Terrestrial||Managed||Disturbed areas||Present, no further details||Natural|
|Terrestrial||Natural / Semi-natural||Natural grasslands||Present, no further details||Natural|
|Terrestrial||Natural / Semi-natural||Scrub / shrublands||Present, no further details||Natural|
|Littoral||Coastal areas||Present, no further details||Natural|
|Littoral||Coastal dunes||Present, no further details||Natural|
Hosts/Species AffectedTop of page
C. intersecta is considered to be a potential agricultural pest. Sternberg (2000) reports that C. intersecta feeds on leaves of young annual seedlings and tissues of forbs and legumes. In Europe, Candidula snails are known to feed on apples, pears, plums and peaches, damaging unripe and forming fruit on the tree. Once damaged, fruit succumb to fungal, bacterial and yeast attack and rot before maturity. C. intersecta also feed on seeds, seedlings and young plants of spring cereals (Godan, 1983).
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page
List of Symptoms/SignsTop of page
|Fruit / external feeding|
|Leaves / external feeding|
|Seeds / external feeding|
|Stems / external feeding|
|Whole plant / external feeding|
Biology and EcologyTop of page
Land snails including C. intersecta are hermaphrodites (Godan, 1983). Many species can store sperm and produce fertile eggs for several weeks after mating. Land snails usually mate and lay eggs in the autumn as conditions are getting cooler and wetter. In temperate climates, the egg stage can be the overwintering period in the life cycle of land snails.
Physiology and Phenology
This species requires calcareous environments for the formation of its shell (Barker, 2002).
C. intersecta populations can reach high numbers and exhibit massing behaviour: large numbers of snails become arboreal, and climb up branches of trees and shrubs, and stems of cereals, to eat, mate, or aestivate and to escape from the ground heat. They are also attracted to cool, dark and humid places and favour environments where calcium is available.
C. intersecta is a polyphagous species feeding on pome and stone fruit, grains, shrubs and new fresh shoots of a range of plants.
C. intersecta can tolerate a range of temperatures (from cool European climates in the UK to dry and hot conditions in southern Australia). It is found at altitudes from 0 to 800 m.
In its natural habitat, C. intersecta is found under stones and in crevices, particularly in limestone areas or in sand dunes (Barker, 1999; 2002). In the UK and Ireland, Gastropod species usually associated with calcareous grassland (including Candidula) are found in sandy areas where the coastal conditions and humid environment (particularly in dune slacks: hollows between the dune ridges) are favourable for their development.
C. intersecta can be found in exposed limestone outcrops, open scrub areas and dry environment in the southern part of Australia. As an agricultural pest, it can feed on pomes (apple, pears) and stone fruit (plum and peaches) and attacks grains and seedlings as they emerge. As a hitchhiker species it can seal itself on the hard surfaces of containers, machinery and vehicles and crawl into dark and cool crevices.
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
|Cf - Warm temperate climate, wet all year||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
Economic ImpactTop of page
No economic impact has been reported in the state of Oregon from the infestations of C. intersecta (Hitchcox, 2007).
Detection and InspectionTop of page
Some species of Mediterranean origin such as Candidula favour calcareous grasslands and sand dunes. These habitats should be checked first for accidental introductions.
Similarities to Other Species/ConditionsTop of page
Gittenberger (1993) notes that C. intersecta differs from Trochoidea geyeri in the finer ribbing of the shell and a microsculpture with relatively prominent spiral striae and no hairpits. In T. geyeri, the body whorl is more regularly inflated. Compared to C. gigaxii, C. intersecta has coarser and less regularly arranged radial 5 riblets and a more roundish umbilicus. Shea (2007) states that C. intersecta is similar to Microxeromagna armillata but is larger and more tightly coiled with less deeply impressed sutures.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
There is little information regarding the specific control (chemical or not) of C. intersecta. Most protocols developed for the control of other land snails could be applied to this species (see the case of the Giant African Snail, USDA-APHIS, 2005).
Cultural control and sanitary measures
Strategies including the reduction of habitat, field burning, and crop rotations are possible.
The use of physical barriers such as copper strips is an option for gastropod control but is not always practical on a large scale.
Molluscicides are often used to target invasive and exotic land snails. They are usually in the form of pellets and are used as baits. Unfortunately some molluscicides have been reported to have non-target effects. Methiocarb and metaldehyde are amongst the potential chemical control options for C. intersecta; however, there is evidence that methiocarb is detrimental to earthworms (Barker, 2002) and some cases of pet poisonings have been reported with metaldehyde. New products available contain iron phosphate (1%) and have proved to be as effective as metaldehyde (Rosetta, 2005).
Small mammals, reptiles, amphibians, birds, and predatory insects feed on land snails and might reduce the population in the environment. Some entomopathogenic nematodes are natural enemies of some slugs and snails and are sold in Europe and Britain (Rosetta, 2005).
ReferencesTop of page
Anderson R, 1996. Species Inventory for Northern Ireland Land and Freshwater Mollusca. Environment and Heritage Service of Northern Ireland.
AnimalBase, 2011. Entry for Candidula intersecta, updated by F. Welter Schultes, 3 November 2011. Online at http://www.animalbase.uni-goettingen. http://www.animalbase.uni-goettingen
AQAS, 2007. Mollusk interceptions at U. Port of Entry. Ad-hoc query report (Jan. 2002 -Feb. 2007). PEST-ID database. Agricultural Quarantine Activity System, USDA-APHIS-PPQ, Riverdale, MD. Mollusk interceptions at U. Port of Entry. Ad-hoc query report (Jan. 2002 -Feb. 2007). PEST-ID database. Agricultural Quarantine Activity System, USDA-APHIS-PPQ, Riverdale, MD. https://mokcs14.aphis.usda.gov/aqas/login
Barker GM, 2002. Molluscs as crop pests [ed. by Barker, G. M.]. Wallingford, UK: CABI Publishing, xii + 468 pp. http://www.cabi.org/CABeBooks/default.aspx?site=107&page=45&LoadModule=PDFHier&BookID=104
CBP, 2007. Mollusks on ceramic tiles., USA: United States Department of Homeland Security, Customs and Border Protection.
Cowie RH; Robinson AC, 2003. The decline of native Pacific island faunas: changes in status of the land snails of Samoa through the 20th century. Biological Conservation, 110:55-65.
Frest JT; Johannes EJ, 2000. A baseline survey of southwestern Oregon, with emphasis on the Rogue and Umpqua River drainages. Year 2000 Report prepared for Oregon Natural Heritage Program, Portland, Oregon. 403 pp.
Gasa E La, 2008. Appendix Q - Plant Pests established in Washington State since 1985. 2008 Climate Change Interim Report, Department of Ecology, Washington State. http://www.gov/climatechange/InterimReport/020608_AppQ_PAWGexotic
Gittenberger E, 1993. On Trochoidea geyeri (Sods, 1926) and some conchologically similar taxa. (Mollusca: Gastropoda Pulmonata: Hygromiidae). Zoologische Mededelingen, Leiden, 67:303-320.
Hausdorf B, 2002. Introduced land snails and slugs in Colombia. Journal of Molluscan Studies, 68:127-131.
Hitchcox M, 2007. Candidula intersecta. Oregon State University, Pacific Northwest Nursery IPM. Candidula intersecta. Oregon State University, Pacific Northwest Nursery IPM. http://oregonstate.edu/dept/nurspest/Candidula
Hitchcox ME, 2014. Survey for the exotic snail Candidula intersecta in Oregon. Survey report update 22 Oct 2014., USA: USDA-Animal and Plant Health Inspection Service, 17 pp.
Mahlfeld K, 2000. Impact of introduced gastropods on molluscan communities, northern North Island. Wellington, New Zealand: Department of Conservation.
Manga Gonzalez MY, 1979. Species of the genus Candidula (Gastropoda, Stylommatophora) in the province of Leon, Spain. (Sobre las especies del genero Candidula Kobelt, 1871, (Gastropoda, Stylommatophora) el la provincia de Leon.) Revista Iberica de Parasitologia, 39(1-4):455-465.
Matos RA de; Corte-Real J, 1993. Distribution patterns of some land snails in Portugal. In: Proceedings of the 9th International Colloquium of the European Invertebrate Survey. Helsinki, 3-4 September 1993. 47-54.
Meissner H; Lemay A; Bertone C; Schwartzburg K; Ferguson L; Newton L, 2009. Evaluation for pathways for exotic plant pest movement into and within the greater Caribbean region. USDA, 267 pp.
ODA, 2008. Oregon Department of Agriculture Plant Division 2008 Annual Report. http://www.oregon.gov/ODA/PLANT/docs/pdf/ippm_annual_report_2008
Rosetta R, 2005. Snails/Slugs. Pacific Northwest Nursery IPM, Oregon State University. Snails/Slugs. Pacific Northwest Nursery IPM, Oregon State University. http://oregonstate.edu/dept/nurspest/slugs
Shea M, 2007. Bash'Em, Burn'Em, Bait'Em. Introduced snails a continuing problem for Australian agriculture. Malacological Society of Australia Newsletter, Australian Shell News, No 131. http://www.malsocaus.org/newsletter/ASN131
Smith BJ; Kershaw RC, 1979. Field Guide to the Non-Marine Molluscs of South Eastern Australia. Canberra, Australia: Australian National University Press, 240 pp.
USDA-APHIS, 2005. New Pest Response Guidelines. Giant African Snails: Snail Pests in the Family Achatinidae. New Pest Response Guidelines. Giant African Snails: Snail Pests in the Family Achatinidae., USA: APHIS. http://www.aphis.usda.gov/import_export/plants/manuals/emergency/downloads/nprg_gas
AnimalBase, 2011. Entry for Candidula intersecta, updated by F. Welter Schultes, 3 November 2011., http://www.animalbase.uni-goettingen
CABI, Undated. Compendium record. Wallingford, UK: CABI
CABI, Undated a. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI
CABI, Undated b. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
Hitchcox M, 2007. Candidula intersecta., Oregon State University, Pacific Northwest Nursery IPM. http://oregonstate.edu/dept/nurspest/Candidula
Mahlfeld K, 2000. Impact of introduced gastropods on molluscan communities, northern North Island., Wellington, New Zealand: Department of Conservation.
Manga Gonzalez M Y, 1979. Species of the genus Candidula (Gastropoda, Stylommatophora) in the province of Leon, Spain. (Sobre las especies del genero Candidula Kobelt, 1871, (Gastropoda, Stylommatophora) el la provincia de Leon.). Revista Iberica de Parasitologia. 39 (1-4), 455-465.
Matos RA de, Corte-Real J, 1993. Distribution patterns of some land snails in Portugal. [Proceedings of the 9th International Colloquium of the European Invertebrate Survey. Helsinki, 3-4 September 1993], Helsinki, 47-54.
Shea M, 2007. Bash'Em, Burn'Em, Bait'Em. Introduced snails a continuing problem for Australian agriculture. In: Malacological Society of Australia Newsletter, Australian Shell News, http://www.malsocaus.org/newsletter/ASN131
Smith BJ, Kershaw RC, 1979. Field Guide to the Non-Marine Molluscs of South Eastern Australia., Canberra, Australia: Australian National University Press. 240 pp.
ContributorsTop of page
11/08/10 Original text by:
CRCNPB Australia, CRC for National Plant Biosecurity, Canberra, Australia
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