MOLLUSCICIDAL ACTIVITY OF THAI INDIGENOUS PLANT EXTRACTS AGAINST POMACEA CANALICULATAWIMOL CHOBCHUENCHOM, SOMRUDEE MOUNGNOI AND DUANGRAT INTORN
Pomacea canaliculata (Lamarck) is one of a number of rice pests that causes serious problems because of rice field devastation. This study shows that the crude extracts of Thai indigenous plants have the capability of killing P. canaliculata (Lamarck). In toxicity tests, aqueous and ethanolic extracts of Thai indigenous plants were tested against P. canaliculata (Lamarck), 3-5 and 20-30 mm in size, and the toxicity was measured by LC50 at 72 h, with a 95% confidence limit. Results showed that for small snails (3-5 mm operculurn diameter), strong activity was observed in aqueous extracts of Bougainvillea spectabilis, Calotropis gigan tea and Croton tiglium and ethanolic extracts of Acaciu cuncinna, Allamanda cat hartica, Alpinia galanga, Bougainvillea spectablitis, Calotropis gigan tea, Cosmos sulphureus, Lantana camara, Murraya paniculata and Sesbania grandiflora. When the toxicity of aqueous and ethanolic extracts of each plant was compared, ethanolic extracts of Alpinia galanga, Calotropis gigan tea and Sesbania grandiflora had significantly greater toxicity than their aqueous extract, whereas the aqueous extract of Mimusops elengi had significantly greater toxicity than the ethanolic extract. For large snails (20-30 mm operculum diameter), strong activity was observed in aqueous extracts of Bougainvillea spectabilis and Calotropis gigan tea, and ethanolic extracts of Alpitzia galanga, Bougainvillea spectabilis, Croton tiglium and Sesbania grandiflora. When toxicity of aqueous and ethanolic extracts of each plants was compared, toxicity of the ethanolic extract of Croton tiglium was significantly greater toxicity than in the aqueous extract, whereas the aqueous extracts of Calotropis gigan tea and Mimusops elengi had significantly greater toxicity than the ethanolic extracts. The Toxicity of various plant extracts with small and large snails was compared and aqueous extracts of Acacia concinna, Allamanda cathartica, Alstonia macrophylla, Bougainvillea spectabilis and Croton tiglium were more toxic to small snails than to large snails at a p-value <0.05. On the other hand, the ethanolic extracts of Calotropis gigan tea, Cosmos sulphureus, Croton tiglium, Mimusops elengi and Murraya paniculata were more toxic for small snails than for large snails at a p-value <0.05. These findings suggest that isolation and purification of the active ingredients in these plants and more field studies should be done in future research.
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