The apple snail plague
The apple snail creates ecologic imbalances and destroys rice paddy fields, eating the sown seed and the rice plantlets, although they also feed on other plants. These snails represent one of the worst gastropod crop pests of the recent times.
The Apple snail species from genus Pomacea, including Pomacea insularum (described by d’Orbigny in 1835), are native of the South America wetlands. They have been widely introduced in Asia and Central and North America to be used as aquarium pets or human food.
The Apple snail species are considered important exotic invasive species due to several characteristics they possess. In favourable conditions, they have a lifespan of 4 years, reach maturity in 2-4 months and each female can lay about 8500-9000 eggs per season. They are highly adaptable to harsh environmental conditions such as low dissolved O2 concentration, low food availability and low temperatures.
It is calculated that the snails currently cause damage in rice fields worldwide equivalent to the loss of tens of billions of Euros each year.
Recently, apple snails entered accidentally the Ebro river delta (Spain). This invasion represents a serious threat to Europe’s wetlands as it is spreading quickly. If the apple snail establishes itself across Europe, the consequences will be devastating for both Europe’s wetlands biodiversity and for rice European production. An evaluation of European Food Security Authority (EFSA) at the end of 2013, included Italy (the Po valley, where rice is mainly cultivated) as an important hub for apple snail dispersal and epidemics.
To date, the measures adopted to combat the apple snail and stop its spread have failed, but in the autumn of 2013 the Autonomous Government of Catalonia explored a new strategy with permission of the European Union. This strategy was to flood 2500 ha of infested fields with sea water in advance of the 2014 growing season. The sea water treatment proved 100% effective in destroying apple snail infestations, however, the residual salinity caused a loss of productivity of about 30% in some fields. The availability of commercial salt tolerant rice lines will prevent the dispersion of this devastating pestall over Europe.