Abstract
A pesticides reduced farming method for irrigated rice cultivation, using the apple snail Pomacea canaliculata (LAMARCK) as a biological weed control agent, has become popular in Japan and some Asian countries. There is no risk assessment of using this snail, although it is invasive for native ecosystems and biodiversity in rice paddy and wetlands of Asian countries. Examination of snail impact on species diversity of vascular plant flora in rice fields of Matsuyama City, was conducted, where snail populations is extending. In rice fields colonized already, mean number of species declined to 40% of ones not yet colonized and aquatic plants markedly decreased.
