<p>The giant African land snail (GALS) has been recorded in every continent except Antarctica and is a major crop pest across the globe since the 1800s. The snail’s worldwide reach has primarily been through human activities. <br /><br />The International Union for Conservation of Nature and Natural resources (IUCN) has listed A. fulica as one of the world’s 100 most invasive species. It is a classic example of an introduced species. <br /><br />The giant African land snail has attracted the attention of mankind for reasons including its large size, supposed medicinal properties and its potential as human or animal food source. It is for these reasons that A. fulica has been spreading globally. Its success as an introduced species is attributed to several factors including high reproductive capacity, voracious feeding habit, inadequate quarantine arrangements and human-aided dispersal.<br /><br />A six-year campaign was taken up to eradicate achatinids from Florida in 1975 at a cost of one million dollars. In Brazil, infestations of this snail resulted in displacement of small agricultural producers to cities, low availability of food, greater food prices and food import. The snail can have profound effects on plant communities, including endangered plant species. <br /><br />In India, the snail was believed to have been introduced in Chowringhee Gardens of Kolkata (formerly Calcutta) in 1847 by British conchologist William Henry Benson and from there on spread to other states (Mead, 1961). According to malacologist Naggs (1997), although Benson brought the snail to India from Mauritius, he handed it to a friend before leaving India and it was the friend who released them into his garden. <br /><br />This perhaps led to the large-scale invasion of the snail into different parts of the country. Recent genetic studies indicate that all A. fulica now occurring throughout South Asia, Southeast Asia and the Pacific region are derived from one haplotype, the source being a single pair of specimens released in Chowringhee in 1847. <br /><br />Having a field day in India<br />The African snail has been thriving in some areas of India for a period of 100-150 years, with no clear evidence of abatement in its pest status which convinced Gude (1914) to consider it as native to India (in The fauna of British India), though introduced. <br /><br />So far, control measures of all types have failed to eradicate this pest, hence an integrated approach to contain the snail is recommended as the ultimate remedy by many scientists world over.<br /><br />The snail was reported for the first time causing damage to ornamental plants and vegetables in Bangalore during the kharif period in Siddappa Gardens close to Lalbagh in 1979. A study this writer conducted in the Bangalore region has shown that the home range of the snail within city limits has increased in nurseries, gardens and near water bodies. Yet its pest/vector status is not fully established as it has not reached the threat level in most regions.<br /><br />The study included interaction and interviews with individual farmers, agriculture scientists, officials of Farm Owners’ Association, nurseries and Horticultural Department officials. <br /><br />Information from a total of 114 villages (57 each from Bangalore and rural districts) were used in the study conducted during 2009-10. Observations were gathered during the monsoon (July-September) and the period just after the monsoon (October-January), before the dry spell began (February/May) in the study region, involving discussions with local people in the areas visited. <br /><br />Ten different mollusc species were found to occur in the study sites. According to the information gathered from respondents during the survey, different malacofauna occur in the area and the most common among these is the GALS, Achatina fulica.<br /><br />Need for a detailed study<br />The marsh slug, Deroceros laeve, was reported for the first time in South India during the study. It could have been dispersed unintentionally along with horticulture goods as it was identified in three horticulture nurseries, two Forest Department nurseries and a private nursery. <br /><br />Thus, the present observations indicate the need for a more detailed survey of terrestrial snails and emphasise the need to monitor invasive malacofauna in the region. Also, a thorough study to understand the impact of A. fulica on endemic snails needs to be undertaken. A. fulica was found to occur in 60 (53 per cent) of 114 villages, followed by Filicaulis alte in 58 (51 per cent), Cryptozona bistrialis in 37 (32 per cent), macrochlamys indica in 29 (25 per cent) and mariella dussumeri in 24 (21 per cent) villages. <br /><br />High densities of GALS population were observed in Hoskote taluk of Bangalore Rural district. Many farmers complained that they could not grow vegetables because they were eaten by A. fulica at the seedling stage. Because the snail is considered sacred and referred to as ‘Basavana hula’ in Kannada, the sacred bull incarnation, there is a stigma attached to its eradication, more so because some farmers believe it is harmless and facilitates crop growth. <br /><br />Observations point to the southern Coucal and mongoose predating on A. fulica. In addition, farmers have observed some species of snake feeding on A. fulica. <br />The extent of the role of such natural enemies in containing the snail population in high-density areas needs to be assessed.<br /><br />Educational campaigns such as ‘Operation Eat Achatina fulica’ have been recommended and practised in some countries with a dense population of A. fulica to promote its consumption and thereby regulate its population. Similar awareness would facilitate the use of snails as feed to poultry, piggery and also to be used in scientific studies. <br /><br />Many alien species of terrestrial molluscs are established in India, data about which is sparse. The potential costs of these alien species on agriculture or the environment are largely unknown in the Indian context, but potentially immense as reported in other parts of the world. <br /><br />Not only are they reported to devour native plants, modifying the environment, but they probably also outcompete native gastropods. It is believed that, with expanding world trade and movement of agri-horticulture goods within India, opportunity for the introduction of new alien species continues to increase perhaps facilitated by lack of external and internal quarantine measures. <br /><br />INVASIVE SNAILS<br />* Any species, including its seeds, eggs, spores or other biological material capable of propagating that species, not native to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health is termed as invasive and exotic species. <br /><br />IMPACT & CONTROL<br />*Degradation of habitat caused by snail feeding and faeces may have an impact on local tourism.<br />* Empty shells filled with water serve as breeding of Vector mosquitos<br />* Recommended molluscicides- mataldehyde, metiocarb,i ron phosphate.<br />* Hand picking, using salt, disruption of soil, sanitation.<br />* There is mild response to snail control using bio-control organisms.<br /></p>
<p>The giant African land snail (GALS) has been recorded in every continent except Antarctica and is a major crop pest across the globe since the 1800s. The snail’s worldwide reach has primarily been through human activities. <br /><br />The International Union for Conservation of Nature and Natural resources (IUCN) has listed A. fulica as one of the world’s 100 most invasive species. It is a classic example of an introduced species. <br /><br />The giant African land snail has attracted the attention of mankind for reasons including its large size, supposed medicinal properties and its potential as human or animal food source. It is for these reasons that A. fulica has been spreading globally. Its success as an introduced species is attributed to several factors including high reproductive capacity, voracious feeding habit, inadequate quarantine arrangements and human-aided dispersal.<br /><br />A six-year campaign was taken up to eradicate achatinids from Florida in 1975 at a cost of one million dollars. In Brazil, infestations of this snail resulted in displacement of small agricultural producers to cities, low availability of food, greater food prices and food import. The snail can have profound effects on plant communities, including endangered plant species. <br /><br />In India, the snail was believed to have been introduced in Chowringhee Gardens of Kolkata (formerly Calcutta) in 1847 by British conchologist William Henry Benson and from there on spread to other states (Mead, 1961). According to malacologist Naggs (1997), although Benson brought the snail to India from Mauritius, he handed it to a friend before leaving India and it was the friend who released them into his garden. <br /><br />This perhaps led to the large-scale invasion of the snail into different parts of the country. Recent genetic studies indicate that all A. fulica now occurring throughout South Asia, Southeast Asia and the Pacific region are derived from one haplotype, the source being a single pair of specimens released in Chowringhee in 1847. <br /><br />Having a field day in India<br />The African snail has been thriving in some areas of India for a period of 100-150 years, with no clear evidence of abatement in its pest status which convinced Gude (1914) to consider it as native to India (in The fauna of British India), though introduced. <br /><br />So far, control measures of all types have failed to eradicate this pest, hence an integrated approach to contain the snail is recommended as the ultimate remedy by many scientists world over.<br /><br />The snail was reported for the first time causing damage to ornamental plants and vegetables in Bangalore during the kharif period in Siddappa Gardens close to Lalbagh in 1979. A study this writer conducted in the Bangalore region has shown that the home range of the snail within city limits has increased in nurseries, gardens and near water bodies. Yet its pest/vector status is not fully established as it has not reached the threat level in most regions.<br /><br />The study included interaction and interviews with individual farmers, agriculture scientists, officials of Farm Owners’ Association, nurseries and Horticultural Department officials. <br /><br />Information from a total of 114 villages (57 each from Bangalore and rural districts) were used in the study conducted during 2009-10. Observations were gathered during the monsoon (July-September) and the period just after the monsoon (October-January), before the dry spell began (February/May) in the study region, involving discussions with local people in the areas visited. <br /><br />Ten different mollusc species were found to occur in the study sites. According to the information gathered from respondents during the survey, different malacofauna occur in the area and the most common among these is the GALS, Achatina fulica.<br /><br />Need for a detailed study<br />The marsh slug, Deroceros laeve, was reported for the first time in South India during the study. It could have been dispersed unintentionally along with horticulture goods as it was identified in three horticulture nurseries, two Forest Department nurseries and a private nursery. <br /><br />Thus, the present observations indicate the need for a more detailed survey of terrestrial snails and emphasise the need to monitor invasive malacofauna in the region. Also, a thorough study to understand the impact of A. fulica on endemic snails needs to be undertaken. A. fulica was found to occur in 60 (53 per cent) of 114 villages, followed by Filicaulis alte in 58 (51 per cent), Cryptozona bistrialis in 37 (32 per cent), macrochlamys indica in 29 (25 per cent) and mariella dussumeri in 24 (21 per cent) villages. <br /><br />High densities of GALS population were observed in Hoskote taluk of Bangalore Rural district. Many farmers complained that they could not grow vegetables because they were eaten by A. fulica at the seedling stage. Because the snail is considered sacred and referred to as ‘Basavana hula’ in Kannada, the sacred bull incarnation, there is a stigma attached to its eradication, more so because some farmers believe it is harmless and facilitates crop growth. <br /><br />Observations point to the southern Coucal and mongoose predating on A. fulica. In addition, farmers have observed some species of snake feeding on A. fulica. <br />The extent of the role of such natural enemies in containing the snail population in high-density areas needs to be assessed.<br /><br />Educational campaigns such as ‘Operation Eat Achatina fulica’ have been recommended and practised in some countries with a dense population of A. fulica to promote its consumption and thereby regulate its population. Similar awareness would facilitate the use of snails as feed to poultry, piggery and also to be used in scientific studies. <br /><br />Many alien species of terrestrial molluscs are established in India, data about which is sparse. The potential costs of these alien species on agriculture or the environment are largely unknown in the Indian context, but potentially immense as reported in other parts of the world. <br /><br />Not only are they reported to devour native plants, modifying the environment, but they probably also outcompete native gastropods. It is believed that, with expanding world trade and movement of agri-horticulture goods within India, opportunity for the introduction of new alien species continues to increase perhaps facilitated by lack of external and internal quarantine measures. <br /><br />INVASIVE SNAILS<br />* Any species, including its seeds, eggs, spores or other biological material capable of propagating that species, not native to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health is termed as invasive and exotic species. <br /><br />IMPACT & CONTROL<br />*Degradation of habitat caused by snail feeding and faeces may have an impact on local tourism.<br />* Empty shells filled with water serve as breeding of Vector mosquitos<br />* Recommended molluscicides- mataldehyde, metiocarb,i ron phosphate.<br />* Hand picking, using salt, disruption of soil, sanitation.<br />* There is mild response to snail control using bio-control organisms.<br /></p>
