Control efficacy of tobacco extract against Pomacea canaliculata Lamarck under high temperature conditions

【Objective】 To investigate the control effect of tobacco extract on Pomacea canaliculata Lamarck under high temperature environment， which could provide scientific basis for improving the utilization efficiency of botanical molluscicides and optimizing the timing of Pomacea canaliculata Lamarck control. 【Method】 Pomacea canaliculata Lamarck at different developmental stages were placed in an outdoor natural light environment in summer （high temperature environment was simulated） and laboratory with air conditioner on all day（simulated room temperature environment）. Treatments included aerated tap water （CK） and tobacco extract on concentrations of 0.2， 0.5， and 1.0 g/L. The effects of high temperature and tobacco extract on the survival， behavioral activity， feeding and growth of Pomacea canaliculata Lamarck were observed， and the activities of antioxidant enzymes and acetylcholinesterase （AChE） in the hepatopancreas were determined. 【Result】 The molluscicidal effect of tobacco extract increased with increasing concentration； 1.0 g/L tobacco extract caused complete mortality of Pomacea canaliculata Lamarck within 6 d. Under 0.5 g/L tobacco extract， the snails had difficulty feeding， and the proportions of individuals with tightly closed opercula and crawling out of water both increased markedly； meanwhile， the activities of superoxide dismutase （SOD）， catalase （CAT）， and AChE activity in the hepatopancreas were induced to increase. High temperature enhanced the effectiveness of tobacco extract in controlling Pomacea canaliculata Lamarck， under the combined stress of 0.5 g/L tobacco extract and high temperature， Pomacea canaliculata Lamarck almost completely lost their motor ability and all died within 3 d. The survival ability of different developmental stages ranked as medium-sized Pomacea canaliculata Lamarck > adult Pomacea canaliculata Lamarck > juvenile Pomacea canaliculata Lamarck. Under normal temperature conditions， 0.2 g/L tobacco extract significantly reduced the food intake of juvenile and medium-sized Pomacea canaliculata Lamarck compared with CK （P<0.05）. High temperature promoted the growth of juvenile and medium-sized Pomacea canaliculata Lamarck under CK， while enhancing the inhibitory effect of 0.2 g/L tobacco extract on the growth of juvenile Pomacea canaliculata Lamarck. 【Conclusion】 High temperature can significantly enhance the control efficacy of tobacco extract against Pomacea canaliculata Lamarck. Tobacco extract has the potential to be developed as a botanical molluscicide. In practice， it is re-commended to apply the extract in combination with high temperature weather and shallow water layer （3-5 cm） management， with precise application during the late rice transplanting period in southern rice-growing regions of China， so as to improve efficacy and reduce dosage.