For a detailed account of management strategies A. fulica please read: Achatina fulica (Giant African Land Snail) Management Information. The information in this document is summarised below.
Preventative Measures: As there is a high risk of Achatina fulica being spread via trade routes there is potential to prevent its spread through international quarantine and surveillance activities. Small incipient populations of A. fulica have been eradicated at various times from California, USA; Florida, USA; Queensland, Australia; Fiji; Samoa; Vanuatu and Wake Island (Abbott 1949, Mead 1961 1979a, Colman 1977 1978, Muniappan 1982, Waterhouse & Norris 1987, Watson 1985, in Raut & Barker 2002). Control costs can range from USD 60 000 dollars for a 7-month procedure, to over USD 700 000 dollars for the eradication in Florida (Muniappan et al. 1986, Smith and Fowler 2003). For the few species in which spontaneous collapse has been repeatedly observed such as A. fulica, the possibility of such an event is warranted as a potential rationale for a do-nothing approach to management (Simberloff & Gibbons 2004).
Physical Control: Collection and destruction of the snails and their eggs has been reported to be effective in Guam, Hawaii, Japan and Sri Lanka, Australia, USA (Peterson 1957c, Mead 1961 1979a, Olson 1973, Colman 1977, in Raut & Barker 2002). Physical barriers that prevent movement of snails include the use of a strip of bare soil around the crop, a fence that consists of a screen of corrugated tin or security wire mesh.
Chemical control: Metaldehyde and/or calcium arsenate were used in early attempts to control A. fulica. A number of new molluscicidal chemicals are now available. The principal toxic effect of metaldehyde is through stimulation of the mucous glands, which cause excessive sliming, leading to death by dehydration; metaldehyde is toxic to slugs and snails both by ingestion and absorption by the ‘foot’ of the mollusk (Prasad et al. 2004). Sodium chloride (common table salt) is an effective dehydrating agent (Prasad et al. 2004). Various molluscicides like metaldehyde are non-selective, thus their use has a chance of endangering the survival of non-target snails, including endemic fauna (Prasad et al. 2004). Please see section 2.1.3 of Barker and Watts (2002) for information on the application of molluscicides.
There is much interest in naturally occurring chemicals as molluscicides. Panigrahi and Raut (1994, in Raut & Barker 2002) have demonstrated that an extract of the fruit of Thevetia peruviana has activity against A. fulica. Prasad and colleagues (2004) found natural softwood cutting fences made of alligator apple (Annona glabra) acted as snail repellents to protect the nursery beds.
Biological Control: rosy wolfsnail (Euglandina rosea) has been introduced throughout much of the introduced range of A. fulica in “biological control programmes” (Mead 1961, Tillier & Clarke 1983, Murray et al., 1988, in Gerlach 2001). The failure of these programmes and the devastating effect that E. rosea has had on many indigenous species is well known (Tillier & Clarke 1983, Clarke, Murray & Johnson 1984, Hadfield 1986, Murray et al. 1988, Cowie 1992, Pearce-Kelly, Clarke & Mace 1994, Coote et al. 1999 2000, in Gerlach 2001). Generalist predators such as E. rosea, Gonaxis quadrilateralis and Platydemus manokwari continue to be dispersed to new areas in misguided attempts to control this invasive gastropod.
Location Specific Management Information
A Government control campaign was launched by the Agriculture Department with the price of molluscicides (methaldehyde bait) subsidised (Connor 2007). Workers from the Agricultural Department set baits for A. fulica.The following actions have been proposed: mechanical picking of snails, public awareness campaigns and education, establish a task force to coordinate eradication, establish legal rights for task force workers to enter property, improve quarantine of plants and other imports, develop detailed budgets and seek funding, establish multi-agency approach, led by government (Dept of Agriculture). Connor (2007) advises the following strategies take place:
- Develop strategic program to prevent/control invasive species
- Continuously educate public about invasive species
- Collaborative effort among all stakeholders
- Use of bait
- Hand removal
- Destruction of eggs
- Encorage residents to keep surroundings clean
- Low grass/ clear up dried leaves and old wood, etc
- Proper drainage (sinks/bathrooms, etc)
- Avoid the introduction of predatory animals
- Rosy wolf snail
- Planarian (Platedemus manokwari)
Because of its now wide distribution and the great size of Brazil, it is impossible to eradicate A. fulica. However, local control remains possible, although it will entail great financial and labor costs (Thiengo et al. 2007). The cost of the eradication of A. fulica can be very expensive. In the USA, the elimination of this pest varied from USD 60 000 to USD 700 000 (Muniappan 1987, Smith & Fowler 2003, in Albuquerque et al. 2008). According to Lauro de Freitas City Hall, lot clearance cost is around USD 3 300 per month (Albuquerque et al. 2008). Albuquerque and colleagues (2008) believe that scrub clearance may represent a good and inexpensive solution to eradicate this pest on a small scale in Brazil. José de Pontes developed a soluble natural non-biocide that is able to attract and exterminate A. fulica that are within a 30 meter distance from the application area.
In 2001 the Sociedade Brasileiro de Malacologia (Brasilian Malacological Society) presented recommendations for the control of A. fulica to the Ministerio da Agricultura e do Abastecimento (MAPA). In 2003, IBAMA (the Brazilian Environment Institute) and MAPA published documents in which cultivation and marketing of A. fulica was considered inadvisable. In 2003 the municipality of Atibaia, Sao Paulo state, enacted a law that forbids rearing, purchase or selling of A. fulica. A similar law was passed in 2004 applying to the entire state of Sao Paulo. In 2005 IBAMA issued Instrucao Normativa no. 73, which forbids rearing of and commerce in A. fulica in Brazil. In 2005 the Ministerio do Meio Ambiente organized in Brasilia the “First
National Symposium on Exotic and Invasive Species”, during which the situation regarding A. fulica in Brazil was discussed (Thiengo et al. 2006).
A national plan for management and control of A. fulica was created by IBAMA and actions under this plan have been implemented since the beginning of 2004. The control method adopted is physical control: collection and destruction of snails and eggs from infested sites, through organised campaigns involving technical staff from local IBAMA and health service offices, local people, students, and teachers. After collection, the snails are crushed using road rolling machinery, put into 2 m ditches, covered with kaolin, and then covered with earth. In Parnamirim, state of Rio Grande do Norte, after five months of efforts, approximately 4000 kg of snails were collected and destroyed, resulting in a significant reduction in the numbers of snails found in the urban part of the municipality (Faraco, unpublished). In addition similar programs have been implemented in Manaus, state of Amazonas, six municipalities in the state of Sao Paulo, two in the state of Rio de Janeiro, and two in the state of Mato Grosso (Thiengo et al. 2007).
The giant African land snail has been eradicated from California where it was present in a localised area in some thousands (Animal and Plant Health Inspection Service 2005)
An eradication program for this invasive species was initiated in Ecuador in 2006, although it was not officially announced (Borrero et al. 2009).
Eradication of the introduction in Florida in the 1960s involved massive use of molluscicides, hand collecting, and extensive public awareness measures (Mead 1979, in Thiengo et al. 2007). The eradication of the A. fulica occurred after it had been established for five years and the cost was over USD 1 million (Animal and Plant Inspection Service 2005). If the snail had been left unchecked the estimated annual loss to Florida would be USD 11 million. The Florida eradication employed both handpicking of snails with the use of granulated chemical bait. Frequent foot by square foot surveys were conducted in the area and over 400 properties were quarantined. Carbaryl drenches were also included (Simberloff 1997, in Cooling 2005). The campaign invovled thousands of hours of labour and it took two to three years before all major infestation sites were discovered and reported (Mead 1979, in Cooling 2005).
Since the local people do not eat A. fulica this alien species goes unchecked (Raut & Barker 2002).
In 1957 the predatory rosy wolfsnail (Euglandina rosea) was introduced into Guam to control A. fulica. Non-target impacts included the consumption of native snails (Hoddle 2004). The predatory flatworm Platydermus manokwari may have been responsible for a 95% decrease in achatinid populations in Guam over 4 years.
In 1955 the predatory rosy wolfsnail (Euglandina rosea) was introduced into Hawaii to control A. fulica. Non-target impacts included the consumption of native snails (Hoddle 2004).
Localised eradication of A. fulica on some Hawaiian islands appears to have been successful (Mead 1979).
Ile aux Aigrettes
A targeted eradication programme is planned as part of a rehabilitation programme on the island. This involves the application of molluscicide. For this to be successful, it will be necessary to have good estimates of population size and distribution of the target species (see Craze & Mauremootoo 2002).
Kosrae (Kusaie) Is.
In the Pacific, incipient populations appear to have been eradicated in Kosrae (Anonymous 1998 2000, in Thiengo et al. 2007), and as of 2006 it has not become established on this island (Thiengo et al. 2007).
Moorea Is. (Society Islands)
In 1977 the predatory rosy wolfsnail (Euglandina rosea) was introduced into Moorea to control A. fulica. Non-target impacts included the consumption of native snails and extinction of Partula species (Hoddle 2004).
The collection and killing of snails is the only local control measure. Most people use salt to kill the snails by dehydration; a popular method is to pack snails in plastic bags and throw them onto roads to be crushed by passing traffic. People living by rivers and irrigation canals throw their daily collections directly into flowing water. The Byans Municipality of Tanahun district initiated an official eradication program of A. fulica in 1993 with the help of public participation by providing 20 Nepalese Rupees per 10 kg incentive to local people. The municipality dumped more than 5.5 metric tones of collected snails on the bank of the Madi river. This practice was followed for a number of years but has since been abandoned and A. fulica continues to be abundant in the area.
New Caledonia (Nouvelle Caledonie)
Attempted control methods include biological controls (Euglandina rosea, Gonaxis quadrilateralis and G. kibweziensis), physical and chemical protection methods, educational programmes, the planting of resistant yam varieties and the application of salt, ash, oil or water in ditches around crops (J. Manaute pers. comm., in Cooling 2005).
Biological control: Two species of predatory snails, the rosy wolfsnail (Euglandina rosea) (originating in Central America) and Gonaxis quadrilateralis (originating in East Africa), were introduced intentionally from Guam in 1974. Euglandina established locally but is not invasive, but Gonaxis did not acclimatise (Gargominy & Bouchet, 1996, in Gargominy et al . 1996).
Physical Control: In 1976 a ten day campaign was run in which snails were collected around Noumea on a large scale involving members of the public, who were paid for snails collected. Approximately 800 000 snails were collected. While these efforts did not eradicate the species it was sufficient to relieve the pressure on native species (CTRDP de Nouvelle Caledonie Undated).
On-going control is costly. Risk management and effects mitigation should prioritise prevention, followed by interception and treatment, early detection and rapid eradication and control efforts should aim to minimise adverse effects on native ecosystems, economic activities and public health. Prohibition of the organism and measures to support this are the first step in preventing the A. fulica from establishing in New Zealand. There is a huge risk of A. fulica being spread and introduced into new locations via trade routes. The snails ability to store sperm is a distinct advantage and could enable a founding population to form from just one individual. The majority of interceptions of A. fulica at ports of entry into Australia and New Zealand have been associated with containers. Most of the snails found were located outside of the containers. Of New Zealand's seaports Auckland had the highest number of containers landed and the most found with the snail, followed by Mt Maunganui. The large majority of giant African snail items brought into New Zealand via passengers and their luggage are declared as ornamental shells.
The Giant African Snail has been classified as an unwanted species in NZ since the Animals Act 1967 and remains classified as such under its replacement the Biosecurity Act. Several international strategies such as the World Conservation Unions Strategy on Invasive Species and the Regional Invasive Species Strategy of the South Pacific Regional Environmental Programme have also addressed the issue of the spread of A. fulica in the region. Biosecurity NZ has identified the following Pacific Island countries as high risk sources of A. fulica: Wallis and Fortuna Islands, Papau New Guinea and Vanuatu (areas where the snail has been historically intercepted from).
To improve the inspection system in New Zealand it has been suggested that these additional countries be added to the high risk status/category: American Samoa, French Polynesia, New Caledonia, Western Samoa, Philippines, Indonesia, Malaysia, Singapore, Bangladesh and South Africa. Supportive measures could include public education, access to information and penalty information, offshore certification to confirm container cleanliness and international harmonisation of biosecurity standards for containers.
New Zealand has a low level of suitability in terms of ecological requirements of the snail, primarily due to the relatively cold winter temperatures, however studies show they may survive in lower temperatures and global warming increases the likelihood of their establishment. The use of a geographic information software package (ArcMap) (based on the factors that limit the growth of A. fulica (moisture levels, temperature and land-cover type)) showed the northern and coastal regions of the North Island are the most likely areas to be colonised successfully by the giant African land snail (Cooling 2005).
Metaldehyde, methiocarb, thidicarb and iron chelate are all registered for use in New Zealand. However, indigenous New Zealand molluscs may be at particular risk to chemical control via baiting. DOC (2002) believe it is likely that Placostylus, Succinea and Archeai and some members of Charpoidae and Puntidae would be likely to eat the baits. Iron chelates could also affect some molluscs as well as isopods, crustacea and arachnida.
Much effort and money can be spent on control and eradication of the snail by commercial businesses, private individuals and the Government. The use of biological control agents is risky and has produced a number of undesirable effects overseas including the extinction of native molluscs. Chemical controls have the potential to affect native species, particularly native molluscs and are unpopular with the public.
Tahiti Is. (Society Islands)
In 1974 the predatory rosy wolfsnail (Euglandina rosea) was introduced into Tahiti to control A. fulica. Non-target impacts included the consumption of native snails and extinction of Partula species (Hoddle 2004).
In the Pacific, incipient populations appear to have been eradicated in Tuvalu (Anonymous 1996a, 1996b, in Thiengo et al. 2007) and as of 2006 it has not become established on this island.
An effort has been made to promote it as a food resource on Upolu, collecting the snails for food being seen as a method of controlling them. However, promoting a pest, for whatever seemingly positive reason, is counterproductive as it may probably encourage the further deliberate spread of the snails around the island. It seems axiomatic that a pest species should not be promoted.
In 1973 the predatory rosy wolfsnail (Euglandina rosea) was introduced into Vanuatu to control A. fulica. Non-target impacts included the consumption of native snails (Hoddle 2004). Small populations of A. fulica have been eradicated in Vanuatu (Raut and Barker 2002).
Wake Island (Eneen-Kio)
In the Pacific, incipient populations appear to have been eradicated in Wake (Raut & Barker 2002, in Thiengo et al. 2007) and as of 2006 it has not become established on this island.
2. Borrero, F.J., A.S.H. Breure, C.C. Christensen, M. Correoso & V.M. Avila. 2009. Into the Andes: Three new Introductions of Lissachatina fulica (Gastropoda, Achatinidae) and its Potential Distribution in South America, Tentacle 17.
4. Civeyrel, L. and Simberloff, D. 1996. A tale of two snails: is the cure worse than the disease? Biodiversity and Conservation 5: 1231-1252.
Summary: A discussion of the introduction of predatory snails (notably Euglandina rosea), in putative attempts to control A. fulica. The devastating consequences on native land snail diversity, especially in the islands of the Pacific.
5. Connor, R.A. 2007. The Case of Achatina fulica and its impact in Anguilla, In: Anguilla Invasive Species workshop report.
6. Cooling, V. 2005. Risk Assessment of the Giant African Snail (Achatina fulica) Bowdich in New Zealand. LPSC 7700 Integrative Report. Unitec New Zealand (Unpublished Report)
8. Cowie, R. H. 2001. Can snails ever be effective and safe biocontrol agents?. International Journal of Pest Management 47: 23-40.
Summary: Discusses the use of land and freshwater snails as biological control agents against other snails and against aquatic weeds. Recommends snails not be used for biocontrol.
9. Craze, P.G. & J.R. Mauremootoo. 2002. A Test of Methods for Estimating Population Size of the Invasive Land Snail Achatina fulica in Dense Vegetation, Journal of Applied Ecology 39(4): 653-660.
10. Desinfestação e Controle do Caramujo Africano. Undated.
Summary: Text in Portuguese. Basic translation available.
11. Hoddle, M.S. 2004. Restoring Balance: Using Exotic Species to Control Invasive Exotic Species, Conservation Biology 18(1): 38-49.
12. IUCN/SSC Invasive Species Specialist Group (ISSG)., 2010. A Compilation of Information Sources for Conservation Managers.
Summary: This compilation of information sources can be sorted on keywords for example: Baits & Lures, Non Target Species, Eradication, Monitoring, Risk Assessment, Weeds, Herbicides etc. This compilation is at present in Excel format, this will be web-enabled as a searchable database shortly. This version of the database has been developed by the IUCN SSC ISSG as part of an Overseas Territories Environmental Programme funded project XOT603 in partnership with the Cayman Islands Government - Department of Environment. The compilation is a work under progress, the ISSG will manage, maintain and enhance the database with current and newly published information, reports, journal articles etc.
13. Mead, A. R. 1961. The giant African snail: a problem in economic malacology. Chicago, University of Chicago Press.
Summary: Major treatise on the worldwide spread of A. fulica, its impacts, and management.
14. Mead, A. R. 1979. Pulmonates volume 2B. Economic malacology with particular reference to Achatina fulica. London, Academic Press.
Summary: Update of Mead 1961.
15. Meyer, W.M. & A.B. Shiels. 2009. Black Rat (Rattus rattus) Predation on Nonindigenous Snails in Hawai‘i: Complex Management Implications, Pacific Science 63(3): 339-347.
16. Prasad, G.S., D.R. Singh, S. Senani & R.P. Medhi. 2004. Eco-friendly way to keep away pestiferous Giant African snail, Achatina fulica Bowdich from nursery beds, Current Science 87(12).
17. Raut, S.K. & G.M. Barker. 2002. Achatina fulica Bowdich and Other Achatinidae as Pests in Tropical Agriculture. In: Barker (Ed.) Molluscs as Crop Pests. CABI.
18. Simberloff, D.& L. Gibbons. 2004. Now you See them, Now you don't! – Population Crashes of Established Introduced Species, Journal Biological Invasions 6(2): 161-172.
19. Thiengo, S.C., F.A. Faraco, N.C. Salgado, R.H. Cowie & M.A. Fernandez. 2007. Rapid spread of an invasive snail in South America: the giant African snail, Achatina fulica, in Brasil, Biol Invasions 9: 693-702.
21. Walker, K. 2006. Giant African Snail (Achatina fulica) Pest and Diseases Image Library. Updated on 13/02/2006 9:44:47 AM.
Summary: PaDIL (Pests and Diseases Image Library) is a Commonwealth Government initiative, developed and built by Museum Victoria's Online Publishing Team, with support provided by DAFF (Department of Agriculture, Fisheries and Forestry) and PHA (Plant Health Australia), a non-profit public company. Project partners also include Museum Victoria, the Western Australian Department of Agriculture and the Queensland University of Technology.
The aim of the project is: 1) Production of high quality images showing primarily exotic targeted organisms of plant health concern to Australia. 2) Assist with plant health diagnostics in all areas, from initial to high level. 3) Capacity building for diagnostics in plant health, including linkage developments between training and research organisations. 4) Create and use educational tools for training undergraduates/postgraduates. 5) Engender public awareness about plant health concerns in Australia.
PaDIL is available from : http://www.padil.gov.au/aboutOverview.aspx, this page is available from: http://www.padil.gov.au/viewPestDiagnosticImages.aspx?id=228 [Accessed 6 October 2006]
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