Golden apple snails in the world: Introduction, impact and control mesures

The golden apple snail (GAS), Pomacea canaliculata (Lamarck) is a large freshwater snail native to tropical and substropical South America that later spread to Taiwan, Japan, Southeast People's Republic of China, and the Philippines. Many potential benefits of GAS have been recognized, including its use as a food source; use in the aquarium trade, for biological control of weeds; as a protein source for fish, ducks, pigs, and crocodiles; and as liquid biofertilizer. In its native environment GAS has not become a major threat to the ecosystem, but it has become an invader in new ecosystems due to its physiological adaptability and ability to move along distance within a water system. Pomacea is now a major pest in rice and taro crops. In Thailand it seriously damages Ipomoea aquatica, a popular vegetable. Heavy economic losses as well as high costs of control have been reported in some Asian countries. Furthermore, Pomacea has threatene d some native aquatic plants in these countries. It acts as a vector for Angiostronghlus cantonensis (ratlong worm), which causes fatal eosinophilic meningo encephalitis in humans. Eradication of GAS has become a umbersome and costly task. Studies have shown that GAS can be controlled by integrating chemical, mechanical, and biological measures at different stages of cultivation. Biological methods would be more effective for GAS control, as it is a source of food for many birds, in particular water birds like ducks, open bills (Anastomus oscitans), the common scope owl (Otos sunica) and greater coucal (Centropus sinensis), and prey birds such as kites and egrets in rice fields. The fish species common carp (Cyprinus carpio) and Piaractus brachypomus effectively predate on GAS. Botanical antisnail preparations such as dried tobacco leaves and neem extracts have been reported to control GAS populations. Many approaches have been tried. Sustainable management of GAS needs exte n ded studies on ecological and biological behavior patterns, which are the main knowledge gaps required to minimize the spread of GAS. Integration of such information and control measures identified so far along with suitable legislation and policies have become a need at present to prevent introduction and to manage the GAS population at non threatening levels, but implementation has been limited due to lack of resources.