Case Study: Golden Apple Snail

The golden apple snail Pomacea canaliculata was introduced from Florida and Latin American to Taiwan in the early 1980s to start an escargot industry. The snail’s fast breeding and adaptability, as well as its high protein content, made it an ideal dietary supplement. Consumers did not react as enthusiastically as snail farmers did, however, and though they were initially expensive, the market value of the snail soon plummeted. Additionally, it was discovered that the golden apple snail was just as likely as the native apple snail to transfer the rat lungworm parasite, which can infect humans and is passed through undercooked snail meat. As the market disappeared, snails were readily discarded and released into the wild. These snails soon spread to rice fields, entering through waterways and irrigation canals.

The golden apple snail has a brachial respiration system that allows it to breathe under water as well as a lung that respirates air. This allows the snail to adapt quickly to changing conditions and expands its ability to search for food, prompting the snail to leave the water when the food supply below the surface is inadequate. Female snails lay up to 500 eggs per week, causing population explosions. Such adaptations, along with high population densities, have made these snails a serious pest in many areas of cultivated rice land in Asia. The snails eat the base of padi seedlings, then consume the aerial leaves and stems, all of which takes an adult snail between three and five minutes.

Snail grazing has devastated rice paddies, costing farmers over one billion dollars in crop losses. Attempts at snail control and eradication are varied. Fields in Taiwan have been treated with tea seed cake powder in an effort to kill the golden apple snails, while nets and special traps placed at outlets in rice fields have been used to prevent entry. Biological control has been relatively successful, with farmers using both catfish and Peking ducklings to help eradicate the snail population.

The blight of golden apple snails continues, however, as snails have spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines. There are indications that they are now invading Australia. A 1989 introduction of golden apple snails to Hawaii wreaked havoc on the rice and taro fields of the islands.

Related Links:
-- Food and Agriculture Organization of the United Nations
^{-- Sarawak Warns of Snail Threat}