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Theba pisanaMüller

A snail that causes severe defoliation threatens the southern U. S. and Mexico

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Name: Theba pisana Müller
Taxonomic Position:
Animalia: Mollusca: Gastropoda: Stylommatophora: Helicidae
Common Names: White garden snail, white Italian snail

Theba pisana has been established in southern California since 1985. Although no documented records exist for North American populations outside of California, the possibility remains for spread of T. pisana to other southern U. S. states and Mexico. Theba pisana is also the most frequently intercepted land snail arriving in shipments from Mediterranean countries.

Issues of Concern: Theba pisana can feed on nearly any plant. It is capable of causing severe defoliation, and can reproduce very rapidly. At high infestation levels, the snails not only compete with livestock for vegetation, the slime the snails produce can also make vegetation unpalatable for livestock.

These snails aestivate (go dormant) over the summer by sealing themselves onto vertical objects such as fence posts and plant stems. The harvest of plants with snails attached causes harvesting machinery to become clogged with shells, and also results in excess moisture and decay in the harvested product.

Pathways: Theba pisana has a strong tendency to climb up and aestivate in shipping containers, which may result in transport of the snail to uninfested areas. The snails may often be difficult for inspectors to detect.

Hosts: A wide variety of plants may be eaten, including citrus, ornamentals, cereal crops, grapevines, and garden crops.


Theba pisana is native to Morocco. It has been introduced into other parts of Africa, Mediterranean Europe and Great Britain, Asia, Australia, the Atlantic Islands, and the United States (San Diego, California area). Specimens from Brazil are in a historic collection at the Academy of Natural Sciences, however there are no subsequent reports in the literature or from communications with Brazil to confirm the distribution so the pest is considered absent.

Quarantines: Theba pisana is quarantine significant in southern U. S. states where the climate is suitable for growth and development

Detection Strategies
Theba pisana prefers open grassland areas with sandy soils near the coast. In these areas, searching should be directed to plants, fences and other vertical surfaces. In shipping yards in these areas, containers should be placed on bearers to minimize contact with the ground, in order to reduce the chance of snails climbing into the containers.

Containers shipped in from areas where the snails are known to exist should be inspected, especially the underside, lids, and corners. Any snails found should be removed and crushed.

Chemical controls may not be effective in the summer, due to the low metabolism of the snails during aestivation. Physical controls in infested areas may include mowing or burning vegetation, plowing or disking the soil, and maintaining good sanitation by disposing of rubbish and debris that may harbor snails.

Snail-infested cargo can be decontaminated with high pressure, freshwater washdown (followed by collection and proper disposal of material removed), live steam washdown, or fumigation by trained and certified applicators.

Useful Links:
University of Florida's Featured Creatures
SARDI Entomology
HYPP Zoology

Warning: The information in this archived item was not confirmed with the appropriate National Plant Protection Organization and is provided solely for informational purposes. Please use this information with caution.

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