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The golden apple snail (GAS) is a dangerous rice pest in Asia




  • The GAS Pomacea canaliculata (Lamarck) is a recently introduced rice pest in Asia. The planting method greatly influences the period of susceptibility to snail damage: wetbed-transplanted 20-day-old seedlings were less damaged than dapog-transplanted 13-day-old seedlings or direct-seeded rice.
    Seedlings 30 days old were more tolerant of snail damage than younger seedlings.
    The GAS Pomacea canalicualata was originally introduced from South America to south-east Asia around 1980s, as a local food resource and as a potential gourmet export item. The markets never developed; the snails escaped or were released, and P. canaliculata became a serious pest of rice throughout many countries of south-east Asia.
    The GAS now is a major rice exotic invasive pest in Asia. The yield loss caused by P. canaliculata in rice was estimated varying from 5 % to 100 % depending on locality and the level of infestation in most Asian countries. In China, GAS was first introduced into Guangdong province of China in 1981 and became a serious pest of rice since 1984.
    In the Philippines, it is considered the number one rice pest and has caused huge economic lossesDuring the 1980’s the introduced snails rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines and there are indications that they are currently invading Australia. Nevertheless, apple snails are considered a delicacy in several regions and they are often sold in Oriental markets for consumption.
     In the 1980’s, GAS Pomacea canaliculata was introduced in Taiwan to start an escargot industry. Such food culture can provided protein for the local population, especially useful for the farmers, who primary live on a rice diet, low in proteins. However, the snails didn’t become a culinary success. It also became quickly clear that the imported species were able to transfer the Angiostrongylus cantonensis (rat lungworm) parasite just like the native apple snail population (Pila).However, the snails did not become a culinary success.
    It was introduced to Hawai‘i in 1989, probably from the Philippines, and for the same reasons as for its initial introduction to south-east Asia.
    Already, introduced P. canaliculata has been implicated in the decline of native species of Pila apple snails in south-east Asia. Also, native species of Pila in thePhilippines are reported to have declined as a result of extensive pesticide applications against introduced P. canaliculata.
    This parasite spends a part of its life cycle in apple snails and can infect humans when the snail isn’t cooked long enough before consumption.  Instead of becoming a food source they escaped, and became a serious pest, posing a real threat to the rice production and the environment. 
    Instead of becoming a valuable food source, the introduced snails escaped and became a serious threat to rice production and the native ecosystems. During the 1980s the introduced snails rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines.
    In 1989 GAS Pomacea canaliculata was introduced in Hawaii to serve as a food source and aquarium pet. Some snails escaped to the wild and turned into a serious pest in the taro and rice fields. Although a few restaurants serve them, the apple snail didn’t become a great gastronomic success here either.
    Recent research reveals the catastrophic nature of the Pomacea invasion in new habitats: the snail herbivory drastically alters the state and function of invaded natural wetlands. When the plants are consumed, nutrients in the system are shunted to phytoplankton instead of the plants which creates dense algal blooms (Carlsson et al in press. 2004). 
    In China, GAS was first introduced into Guangdong province in 1981 and became a serious pest of rice since 1984 (Halwart, 1994). The first record for GAS infestation on rice and Zizania latifolia in Yuyao City of Zhejiang province was found in 2002, and became a serious pest in rice and Z. latifolia fields in 2004 (Pan et al., 2008). 
    Z. latifolia, is one of the most important aquatic and economic vegetable crops cultivated in the Southeast China since ancient time (Guo, 2007). Nowadays, around 100 thousands hectares of Z. latifolia were planted in more than ten provinces in China(Chen, 1991; Zhai et al., 2001).
    The yield loss caused by GAS in rice was estimated varying from 5 % to 100 % depending on locality and the level of infestation in most Asian countries (Halwart, 1994; Naylor, 1996).
    Numerous measures have been taken to control GAS, in Z. latifolia fields. The molluscicide was usually used to kill GAS with a serious environmental and human health consequence, and the hand-picking was proved to be a time-consuming work (Yu et al., 2001; Chen et al., 2003). Thus, local farmers did not adopt these methods extensively for GAS control.
    Recently, the biological control was applied to suppress the occurrence of GAS by releasing biological agents such as fishes and ducks in crop fields. However, due to the low efficiency of fishes and ducks, especially for controlling the adult GAS (Yoshie and Yusa, 2008), the Chinese soft-shelled turtle (Pelodiscus sinensis), was tentatively selected as a new biological agent to control GAS in Z. latifolia field (Zheng et al., 2005). 
    P. sinensis is widely distributed in Eastern Asia and usually take up 4 ~ 6 years to reach sexual maturity adulthood. P. sinensis consumes insect larvae, small fish, small aquatic animals and seeds of marsh plants (Nuangsaeng and Boonyaratapalin, 2001). Furthermore, P. sinensis is of high commercial value and is commonly cultured in Malaysia, Indonesia and China for food consumption (Jia et al., 2005). The objective of this study is to quantify the role of P. sinensis in biologically controlling GAS in Z. latifolia field.
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