Deroceras reticulatum (grey field slug)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Threatened Species
- Risk and Impact Factors
- 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
- Deroceras reticulatum
Preferred Common Name
- grey field slug
Other Scientific Names
- Agriolimax agrestis
International Common Names
- English: field slug; gray field slug
- Spanish: babosa gris; babosa pequena; limacido reticulado
- French: coitron; limace grise
Local Common Names
- Denmark: net-agersnegel
- Germany: gemeine Ackerschnecke; genetzte Ackerschnecke; Tauschnecke
- Italy: lumacone campestre
- Netherlands: gevlekte akkerslak
- DERORE (Deroceras reticulatum)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Pulmonata
- Order: Stylommatophora
- Suborder: Sigmurethra
- Unknown: Limacoidea
- Family: Limacidae
- Genus: Deroceras
- Species: Deroceras reticulatum
Notes on Taxonomy and NomenclatureTop of page Müller first described the grey field slug in 1774. Only recently, it was realized that this group comprises several similar species, and the use of biochemical and molecular tools is likely to change the taxonomy of this group in the future. Until now, no agronomically relevant differences among these similar species have been reported.
DescriptionTop of page Egg
White, slightly transparent, soft-shelled, diameter ca 1 mm. Deposited in clusters in soil cavities. Similar to eggs of other slugs.
Important external taxonomic characters of slugs are the mantle (dorsal cover of the body, behind the head), the pneumostome (respiration hole, always located on the right hand side of the mantle) and the keel (dorsal ridge on the body). In Agriolimacidae, the pneumostome is located in the posterior half on the mantle. The wrinkles on the mantle are concentric. There is a keel at the posterior end, extending over approximately one-third to one-half of the body.
The colour of D. reticulatum ranges from beige to dark brown. Body colouring can be plain, or with reticular or spotted patterns. The animal grows continuously, retaining the same habitus throughout its life cycle. Hatchlings are ca 3-4 mm long when stretched out. Adults are 3-5 cm long, and weigh 0.5-1 g. D. reticulatum is soft-bodied, except for an invisible, internal shell that is 2-5 mm wide. Some Deroceras spp. can only be distinguished by dissection.
In the resting position, the body is contracted hemisperically and the tentacles are retracted. When the animal is disturbed, it escapes. During locomotion and feeding, the body and tentacles are stretched out. During locomotion, D. reticulatum secretes a fine, transparent mucus trail. When the animal is heavily disturbed, it secretes white mucus on the body surface.
DistributionTop of page D. reticulatum was originally endemic to the palaearctic and was introduced by man to other areas such as North America and Australasia (South, 1992).
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Turkey||Present||YIldIrIm and KebapçI, 2004|
|USA||Present||Godan, 1979; South, 1992|
|-California||Present||Ley et al., 2014|
|Argentina||Present||Martín et al., 2009|
|Austria||Widespread||Kerney et al., 1979; Fischer and Reischütz, 1998|
|Belgium||Widespread||Kerney et al., 1979|
|Bulgaria||Present||Georgiev et al., 2003|
|Croatia||Present||Grubi?ic et al., 2008|
|Czech Republic||Present||Kerney et al., 1979|
|Denmark||Present||Kerney et al., 1979|
|Faroe Islands||Present||Kerney et al., 1979|
|Finland||Present||Kerney et al., 1979|
|France||Widespread||Kerney et al., 1979; Hommay, 1995|
|Germany||Present||Kerney et al., 1979|
|Hungary||Present||Kerney et al., 1979|
|Iceland||Present||Kerney et al., 1979|
|Ireland||Present||Kerney et al., 1979|
|Liechtenstein||Present||Kerney et al., 1979|
|Luxembourg||Present||Kerney et al., 1979|
|Netherlands||Present||Kerney et al., 1979; Ester and Nijënstein, 1996|
|Norway||Present||Kerney et al., 1979|
|Poland||Present||Kerney et al., 1979|
|Russian Federation||Present||Present based on regional distribution.|
|-Northern Russia||Present||Godan, 1979|
|Slovakia||Present||Kerney et al., 1979|
|Sweden||Present||Kerney et al., 1979|
|Switzerland||Widespread||Kerney et al., 1979|
|UK||Widespread||Kerney et al., 1979; Glen et al., 1991|
|-Channel Islands||Present||Kerney et al., 1979|
|New Zealand||Present||Barker, 1989|
HabitatTop of page D. reticulatum occurs most frequently in grassland, arable and vegetable fields and private gardens. However, it may survive in almost any other habitat (except for arid zones) in low numbers. Grass and woodland are its natural habitats.
Habitat ListTop of page
Hosts/Species AffectedTop of page In economical terms, D. reticulatum is the most important pest slug worldwide. D. reticulatum is extremely polyphagous and has been reported to attack a very broad range of crops, if soil and climatic conditions are favourable. However, most of the economically relevant damage occurs in a limited number of crops. In addition to these crops, it also regularly causes damage to vegetable plantlets, many ornamentals and herbs, which are grown outdoors or in greenhouses. D. reticulatum attacks plant parts above and below ground.
In many crops, slug attack is only dangerous if it occurs during a well defined, susceptible life stage of the crop. However, this susceptible stage is not the same for all crops: in wheat, this is the seed stage; in rape, maize, sugarbeet, soyabean and many vegetables it is the seedling stage; in green asparagus, it is the time just before the stems grow out of the soil; in potato, it is the period from tuber formation to harvest; in strawberries, it is the time of fruit ripening. In many vegetables, slug feeding shortly before harvest affects quality through feeding holes, mucus trails or slugs present inside the vegetables.
Overviews over damage by D. reticulatum can be found in Godan (1979), Port and Port (1986), South (1992) and Hammond (1996).
Host Plants and Other Plants AffectedTop of page
|Asparagus officinalis (asparagus)||Liliaceae||Other|
|Beta vulgaris var. saccharifera (sugarbeet)||Chenopodiaceae||Main|
|Brassica napus var. napus (rape)||Brassicaceae||Main|
|Brassica oleracea var. gemmifera (Brussels sprouts)||Brassicaceae||Other|
|Daucus carota (carrot)||Apiaceae||Main|
|Fragaria vesca (wild strawberry)||Rosaceae||Other|
|Glycine max (soyabean)||Fabaceae||Main|
|Hordeum vulgare (barley)||Poaceae||Main|
|Lactuca sativa (lettuce)||Asteraceae||Other|
|Solanum tuberosum (potato)||Solanaceae||Main|
|Trifolium repens (white clover)||Fabaceae||Main|
|Triticum aestivum (wheat)||Poaceae||Main|
|Zea mays (maize)||Poaceae||Main|
Growth StagesTop of page Flowering stage, Fruiting stage, Post-harvest, Pre-emergence, Seedling stage, Vegetative growing stage
SymptomsTop of page Very different symptoms are caused in different crops, at their worst, plants may be completely devoured and slugs can be seen on or inside the crop.
List of Symptoms/SignsTop of page
|Fruit / external feeding|
|Fruit / frass visible|
|Growing point / dead heart|
|Growing point / external feeding|
|Leaves / external feeding|
|Leaves / frass visible|
|Roots / internal feeding|
|Seeds / frass visible|
|Stems / distortion|
|Vegetative organs / internal feeding|
|Whole plant / cut at stem base|
|Whole plant / external feeding|
Biology and EcologyTop of page D. reticulatum is hermaphroditic, therefore all individuals can lay eggs. There is still some debate about the life cycle of D. reticulatum (South, 1992). It seems that in Central Europe, most adults lay eggs in spring (around early April) and die soon after. The eggs hatch after approximately 3-4 weeks. Slugs grow continuously and mature in summer-autumn. The majority of individuals overwinter as adults, and the life cycle continues. However, some adults may also lay eggs in autumn and either eggs or hatchlings may overwinter. Therefore, populations of D. reticulatum often contain a certain proportion of abnormally small or large individuals, the life cycle of which is asynchronous to the rest of the population. Under favourable climatic conditions, or in more favourable regions than Central Europe, two generations per year may be the regular case rather than the exception.
D. reticulatum is found inside the soil during daytime. It does not burrow holes by itself, but uses existing small crevices and earthworm holes. At dusk, it comes to the soil surface and climbs onto the vegetation. With the onset of daylight, it hides in the soil. It may stay above ground in daytime during periods of heavy rainfall.
D. reticulatum overwinters in soil. At temperatures just above freezing, it is already active and can therefore be seen all year round.
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Megaselia aequalis||Parasite||Ayre, 2001|
Notes on Natural EnemiesTop of page A large number of mammals, birds, reptiles and amphibians has been recorded to feed on slugs, and in particular on D. reticulatum. However, slugs make up a very small fraction of their entire diet, and they probably do not contribute much to the regulation of slug populations. Many carabid beetles are known to feed on slugs or on slug eggs. ELISA tests have shown that in some carabid species, at least every second beetle had eaten slugs prior to testing (Symondson and Liddell, 1993). Whether carabids attack primarily living, moribund or dead slugs is currently under investigation. A large number of plathelminths and nemathelminths have been recorded as parasites of slugs. For overviews of natural enemies of slugs, see Stephenson and Knutson (1966), Baronio (1973), Godan (1979), Mead (1979) and South (1992).
Frequently used biocontrol agents such as Bacillus thuringiensis (various strains), Steinernema feltiae and Heterorhabditis sp. do not parasitize D. reticulatum (Wilson et al., 1994; Kienlen et al., 1996). The nematode Phasmarhabditis hermaphrodita is an effective biocontrol agent for slugs.
ImpactTop of page D. reticulatum is a serious pest of winter wheat, winter barley, oilseed rape, sugarbeet and potato in Northern Europe, regularly causing severe losses. In Central Europe, North America and other areas, the same crops are less frequently or less severely attacked (Port and Port, 1986; South, 1992).
A serious pest of maize and soybean in Northern America, regularly causing severe losses in fields with reduced tillage or no tillage (Hammond, 1996).
A serious pest of many horticultural crops in wet climates, regularly causing severe damage. A significant pest in many temperate regions worldwide, periodically causing severe losses when weather conditions are favourable.
A pest of pastures mainly in England, UK, and New Zealand, interfering with the establishment of newly sown pastures, or selectively reducing legumes.
Threatened SpeciesTop of page
Risk and Impact FactorsTop of page Impact mechanisms
Detection and InspectionTop of page Slugs are mostly nocturnal, with a peak of activity just after dusk (Hommay, 1995). During heavy rain, they may also be active in daytime. During these periods, D. reticulatum can be observed on the soil surface and on crops.
In many regions with a temperate climate, D. reticulatum is almost omnipresent. Whether slug damage occurs is determined by climatic conditions, which may favour or restrict its activity during the susceptible phase of the crop, but also by slug population density (Young and Port, 1991; Young et al., 1991). Various refuge traps are in use, for example, ceramic tiles, plant pot saucers, hardboard and wood (Hommay and Briard, 1988; Young, 1990). All these traps are laid out on the soil with or without bait (bran, for example) or slug pellets, and are regularly inspected for the presence of slugs. A defined quantity of slug pellets applied to a certain area may serve the same purpose. There is no general agreement regarding the best trapping method for slugs; the relationship between slug counts and expected damage is not thoroughly known.
Similarities to Other Species/ConditionsTop of page Species
Arionidae: pneumostome located in the anterior half on the mantle, mantle with granular structure, no keel. Animals are sticky when touched, and contract when disturbed.
Milacidae: keel extends over the entire length of the body. The body of Tandonia budapestensis is dark brown, while the keel is yellowish. T. budapestensis lives largely underground and is, therefore, mainly a pest in winter wheat and potato.
Other Agriolimacidae: Some Deroceras spp. can only be distinguished by dissection.
Feeding by D. reticulatum is similar to feeding by other slug species. Only if slugs are observed, can damage be attributed to this species.
Cereals: attacked seeds do not germinate. This may be confused with seedborne diseases or with unfavourable climatic or soil conditions. Slug damage to cereals normally occurs in patches, alternating between 0 and 100% germination. In areas of heavy slug attack, slugs are visible on the soil surface at dusk, during the night or during rain.
Potato: slug boring in potato tubers may be confounded with feeding by wire worms (Agriotes spp.) or with 'dry core' (growth deformations by Rhizoctonia solani). However, wire worms bore holes of constant diameter, while slugs often make small cavities inside potato tubers. Sometimes, resting slugs or slug eggs can be found within potato tubers. Growth deformations by R. solani are usually 2-10 mm deep, but never extend into the whole tuber. Often, they are filled with black, dry tissue. In addition, potato tubers attacked by R. solani show black spots on the skin.
Prevention and ControlTop of page
Ploughing and other methods of soil cultivation significantly reduce slug populations. In recent years, soil cultivation has often been reduced, and slug populations have increased (Hammond, 1996). Slug damage to winter wheat may be reduced by preparing a fine seed-bed and by sowing at greater depth than usual (Glen et al., 1989, 1990). Crop rotation affects levels of slug damage. For example, large populations of D. reticulatum build up in oilseed rape; if winter wheat is sown afterwards, it is at elevated risk of slug damage (Port and Port, 1986; Port, 1989).
In oilseed rape, the so-called '00-varieties' are more susceptible to slug attack than older varieties (Glen et al., 1990; Giamoustaris and Mithen, 1995; Byrne and Jones, 1996). Varietal differences in susceptibility to slugs have also been reported for potatoes (Port and Port, 1986; South, 1992) and wheat (Spaull and Eldon, 1990). In agricultural practice, however, choice of varieties is made on criteria other than resistance to slugs.
In the future, genetic engineering of crops using proteinase inhibitors might help to keep slug damage low (Walker et al., 1998).
Phasmarhabditis hermaphrodita is an effective biocontrol agent for slugs (Wilson et al., 1993; Glen et al., 1996). This nematode is mass-reared and commercially distributed as dauer-larvae formulated in clay. The dauer-larvae are dissolved in water and applied to the soil, where they attack a range of pest slugs. P. hermaphrodita has been successfully applied to a number of crops in England, UK (Wilson et al., 1994, 1995). In Switzerland and Germany, the application of P. hermaphrodita was less successful (Speiser and Andermatt, 1996; Jäckel, 1999). Whether this was caused by a less favourable soil or climate, or by the occurrence of less susceptible slug species is unclear. D. reticulatum is highly susceptible to P. hermaphrodita (B Speiser, FiBL, Frick, Switzerland, unpublished data).
Chinese ducks are successfully used to control slugs in horticultural crops (B Grimm, Institute of Zoology, Graz, Austria, personal communication; B Speiser, FiBL, Frick, Switzerland, unpublished data) but their use is limited by the labour requirements of herd management. The use of ducks for control of snails is described by Sakovich (1996).
Bait pellets are normally used for chemical control of D. reticulatum. These contain either metaldehyde or a carbamate as the active ingredient. The pellets are broadcast on the soil, or drilled into the soil together with the seeds. Slug pellets are often applied preventively, because slug damage is most severe during rain, when tractors should not drive through the fields.
Early Warning Systems
Because of the wide range of different crops at risk, and because of the worldwide distribution of D. reticulatum, there is no general model of slug activity or warning system available. For arable crops in England, UK, models for the prediction of slug damage are developed (Young et al., 1993).
ReferencesTop of page
Byrne J, Jones P, 1996. Responses to glucosinolate content in oilseed rape varieties by crop pest (Deroceras reticulatum) and non-pest slug species (Limax pseudoflavus). Tests of Agrochemicals and Cultivars, 17:78-79.
Castillejo J, 1996. Las babosas come plaga en la agricultura. Claves de identification y mapas de distribucion. Revista Real Academia Galega de Ciencias, 15:93-142.
Chabert A, Guinot J, Tisseur M, 1997. Suivi des populations de limaces au champ. Phytoma, 497:16-20.
Ester A, Nijënstein J, 1996. Molluscicidal seed treatment of barley, wheat and perennial ryegrass to control the field slug (Deroceras reticulatum). Netherlands Journal of Agricultural Science, 44:241-248.
Fischer W, Reischütz PL, 1998. GrundsStzliche Bemerkungen zum Schneckenproblem. Die Bodenkultur, 49:281-292.
Georgiev DM, Kostadinova A, Georgiev BB, 2003. Land snails in the transmission of protostrongylids on pastures in Southern Bulgaria: variability of infection levels related to environmental factors. Acta Parasitologica, 48(3):208-217.
Giamoustaris A, Mithen R, 1995. The effect of modifying the glucosinolate content of leaves of oilseed rape (Brassica napus ssp. oleifera) on its interaction with specialist and generalist pests. Annals of Applied Biology, 126(2):347-363.
Glen DM, Wilson MJ, Hughes L, Cargeeg P, Hajjar A, 1996. Exploring and exploiting the potential of the rhabditid nematode Phasmarhabditis hermaphrodita as a biocontrol agent for slugs. Slug & snail pests in agriculture. Proceedings of a Symposium, University of Kent, Canterbury, UK, 24-26 September 1996., 271-280.
Hammond RB, 1996. Conservation tillage and slugs in the U.S. corn belt. In: Henderson IF, ed. Slug & Snail Pests in Agriculture. Farnham, UK: British Crop Protection Council, 31-38.
Hommay G, Briard P, 1988. Apport du piegage dans le suivi des peuplements de limaces en grande culture. Haliotis, 18:55-74.
JSckel B, 1999. Methoden des biologischen Pflanzenschutzes als Beitrag zum integrierten Pflanzenschutz in der Grossstadt. Gesunde Pflanzen, 51:167-175.
Kerney MP, Cameron RAD, Jungbluth JH, 1979. Die Landschnecken Nord- und Mitteleuropas. Hamburg, Germany: Paul Parey.
Kienlen J, Gertz C, Briard P, Hommay G, Chaufaux J, 1996. Recherche de la toxicité de diverses souches de Bacillus thuringiensis Berliner vis-à-vis de trois espFces de limaces. Agronomie, 16:347-353.
Ley, I. T. de, McDonnell, R. D., Lopez, S., Paine, T. D., Ley, P. de, 2014. Phasmarhabditis hermaphrodita (Nematoda: Rhabditidae), a potential biocontrol agent isolated for the first time from invasive slugs in North America., 16(10), 1129-1138. http://booksandjournals.brillonline.com/content/journals/10.1163/15685411-00002838 doi: 10.1163/15685411-00002838
Martín SM, César II, Liberto R, 2009. Distribution of Deroceras reticulatum (Müller, 1774) (Pulmonata Stylommatophora) in Argentina with first record of the Reserva de Usos Múltiples Isla Martin Garcia, Río de la Plata superior. Brazilian Journal of Biology, 69(4):1115-1119. http://www.bjb.com.br
Mead AR, 1979. Biological control. In: Frette V, Peake J, eds. Pulmonates. London, UK: Academic Press.
Port CM, Port G, 1986. The biology and behaviour of slugs in relation to crop damage and control. Agricultural Zoology Reviews, 1:255-299.
Port GR, 1989. Natural and cultural regulation of slug populations. Aspects of Applied Biology, 22:297-306.
Sakovich NJ, 1996. An integrated pest management (IPM) approach to the control of the brown garden snail, (Helix aspersa) in California citrus orchards. In: Henderson IF, ed. Slug & Snail Pests in Agriculture. Farnham, UK: British Crop Protection Council, 283-287.
Speiser B, Andermatt M, 1996. Field trials with Phasmarhabditis hermaphrodita in Switzerland. In: Henderson IF, ed. Slug & Snail Pests in Agriculture. Farnham, UK: British Crop Protection Council.
Stephenson JW, Knutson LV, 1966. A résumé of recent studies of invertebrates associated with slugs. Journal of Economic Entomology, 59:356-360.
Symondson WOC, Liddell JE, 1993. The detection of predation by Abax parallelepipedus and Pterostichus madidus (Coleoptera: Carabidae) on Mollusca using a quantitative ELISA. Bulletin of Entomological Research, 83(4):641-647; 34 ref.
Turner H, Kuiper JGJ, Thew N, Bernasconi R, Ruetschi J, Wuthrich M, Gosteli M, 1998. Atlas of the Mollusca of Switzerland and Liechtenstein. Atlas der Mollusken der Schweiz und Liechtensteins., 527 pp.
US Fish and Wildlife Service, 2014. In: Holocarpha macradenia (Santa Cruz tarplant). 5-Year Review: Summary and Evaluation. US Fish and Wildlife Service, 48 pp.. http://ecos.fws.gov/docs/five_year_review/doc4365.pdf
Walker AJ, Glen DM, Shewry PR, 1998. Purification and characterization of a digestive cysteine proteinase from the field slug (Deroceras reticulatum): a potential target for slug control. Journal of Agricultural and Food Chemistry, 46(7):2873-2881.
Wilson MJ, Glen DM, George SK, Pearce JD, Wiltshire CW, 1994. Biological control of slugs in winter wheat using the rhabditid nematode Phasmarhabditis hermaphrodita. Annals of Applied Biology, 125(2):377-390.
Wilson MJ, Glen DM, Hughes LA, Pearce JD, Rodgers PB, 1994. Laboratory tests of the potential of entomopathogenic nematodes for the control of field slugs (Deroceras reticulatum). Journal of Invertebrate Pathology, 64(3):182-187.
Wilson MJ, Glen DM, Wiltshire CW, George SK, 1994. Mini-plot field experiments using the rhabditid nematode Phasmarhabditis hermaphrodita for biocontrol of slugs. Biocontrol Science and Technology, 4(1):103-113.
Young C, 1996. Metal chelates as stomach poison molluscicides for introduced pests, Helix aspera, Theba pisana, Cernuella virgata and Deroceras reticulatum in Australia. Slug & snail pests in agriculture. Proceedings of a Symposium, University of Kent, Canterbury, UK, 24-26 September 1996., 237-243.
Distribution MapsTop of page
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