Invasive Species: Apple Snail

An apple snail (Pomacea canaliculata), also known as a miracle snail

Apple snails are native to the Amazon basin on down to parts of Argentina and are quite large-bodied, growing up to ten centimeters. They have become invasive in a large swath of South and Eastern Asia, as well as Guam, the Dominican Republic, Papua New Guinea, Hawaii, and parts of the continental United States. Introduction has been through the aquarium trade, the nursery trade as eggs attached to plants,and through attempts to use them as a food source. They are also known to escape captivity.

The first transports of this species out of its native range began in the 1980's. After attempts to sell the snails as food, they escaped and began becoming crop pests. The species is known to feed on such plants as rice and taro, causing major damage to important food sources, but they also feed on water chestnut, lotus, and other plants. Since they are aquatic, the species spreads quickly and easily in watery environments. They pose a threat to native plant species in and have been linked to the decline of several species of native snail. Mainly due to crop damage, the economic losses these snails have caused in some countries are huge.

Egg mass, scale 5cm

The most important management method thus far is prevention. Spread of the snails must be prevented, particularly to potentially vulnerable areas such as wetlands in India and Australia. Simple things such as copper barriers have proven effective at preventing spread of infestations. Eradication of the pest is done where possible, but cannot be done when there are too many snails. As much as possible, egg masses and hatched snails are removed from effected areas. So far this has been the most viable form of control. Other methods, such as pesticides and biological controls via predators, have not worked out so well. One big concern for any of these methods involves concerns over the environment. Hand removal, on the other hand, as minimal effect if any.

This species is currently on the list of 100 World's Worst Invasives at #73. 

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