Apple snails are characterized by large, round snail shells that have a thin shell cover. In addition to the long antennae above the eyes, there is a second pair of antennae on the mouth. Since apple snails belong to the lung snails, they have to fill up their air supply about once an hour. To get air they form a skin fold on the side of the body to a closed tube which they stretch to the water surface.
The main food source of apple snails are aquatic plant species, and here they have a wide host plant spectrum. When food is scarce, they also feed on algae, detritus, small crustaceans, fish spawn, etc. In Asia, introduced apple snail species threaten the biodiversity and functionality of aquatic ecosystems (see EFSA risk assessment). In the EFSA risk assessment, the potential impact on the environment in the EU is assessed as massive. In addition to marsh and aquatic plants, Pomacea species also eat rice.
The family of apple snails or Ampullariidae originates from South or Central America and occurs worldwide in many tropical and subtropical regions, as well as temperate regions (e.g. in Argentina and in Japan). Species of the genus Pomacea are often kept in aquaria.
Climatic comparisons of the southernmost range in Paso de las Piedras (Argentina) with Europe show extensive climatic similarity (>80%) with southern, western and parts of central Europe, especially if a warming of +2 °C from the 1961-1990 average climate values is assumed (see EFSA Opinion). EFSA therefore assesses the risk of establishment in river courses and channels in the areas at risk as high.
There is uncertainty regarding the possible northern limit of spread of the apple snail in Europe. The tightly fitting gill cover allows the snails to survive unfavorable conditions (drought, cooler periods) for several months. In the northernmost distribution area of Japan, P. canaliculata hibernates at water temperatures of 2 °C in the sediment of watercourses.
Details of the current distribution range can be found here:
Propagation and transmission
Spread by natural means:
- Small-scale through the active foraging of snails.
- Locally by water currents
- Trade in snails
- "Disposal" from aquariums into natural watercourses is thought to be the main route of dispersal
- Egg-laying on boat hulls led to the spread of the apple snail population in Asia; apple snails attached to boats have also been found in the Ebro Delta
- Trade in aquarium plants to which egg clutches adhere
Prevention and control
The Official Plant Protection Services of the Federal Provinces are responsible for carrying out controls to ensure compliance with the measures described in their territory. In case of a suspected occurrence of the apple snail in waters in Austria, this must be reported to the Official Plant Protection Service of the federal state.
With the implementing decision 2012/697/EU of 08.11.2012, the European Commission has taken protective measures to prevent the introduction and spread of snails of the genus Pomacea in the EU. The protective measures include both an import ban on snails of the genus Pomacea and movement restrictions on planting material that can only grow in water or in soil that is permanently saturated with water.
Why were protective measures imposed?
In 2009, the apple snail(P. insularum) was found in the Ebro delta in the province of Tarragona in Catalonia (Spain), and the following year also in rice fields. It spread rapidly and colonized about 600 ha of rice fields (20 km along the Ebro River and 130 km along irrigation canals, respectively) in October 2011. (see also EPPO Global Database). In 2011, the Spanish authorities took emergency measures - based on a national risk assessment - to prevent further introduction and spread of the apple snail. On behalf of the EU Commission and based on the Spanish risk assessment, EFSA prepared a scientific opinion on the risk of the apple snail for the EU in spring 2012.
EFSA Panel on Plant Health (PLH); Scientific Opinion on the evaluation of the pest risk analysis on Pomacea insularum, the island apple snail, prepared by the Spanish Ministry of Environment and Rural and Marine Affairs. EFSA Journal 2012;10(1):2552. [57 pp.] doi:10.2903/j.efsa.2012.2552.
Specific requirements for importation into the EU.
Snails of the genus Pomacea may not be imported into the EU.
In addition, planting material (excluding seeds) of plants that grow only in water or in soil permanently saturated with water (e.g. aquarium plants) may be imported into the EU only if a phytosanitary certificate has been issued for the consignment. This must confirm that the plants were inspected immediately prior to export and found to be free of the apple snail. In addition, the plants are subjected to a health inspection at the place of import (in particular, inspection for apple snail eggs).
Conditions for movement in the EU
The movement (trade) of apple snails in the EU is prohibited.
Aquarium plants originating from demarcated areas (= infestation areas of the apple snail within the EU) require a plant passport for movement to non-demarcated areas.
Note that the requirements for import and movement concern all species of the genus Pomacea .
Last updated: 11.09.2023