Research On The Effects And Mechanism Of Molluscacidal With Rongbao

Objective:To evaluate the effects of molluscacidal by Rongbao,to explore the optimal dosage and methods of application in the field;To research effective ingredients and molluscacidal effects of Rongbao;To explore the role of effective components of Rongbao in causing the histological changes of Oncomelania,and research the mechanism of the molluscacidal by Rongbao,in order to provide a scientific basis for using molluscacider.Methods:Observations were carried out on molluscacidal effects of Rongbao by using immersian and spraying and dusting in laboratory and field experiments.Meanwhile field molluscacidal experiments were conducted with mechanical power duster and the molluscacidal effects were observed.The leaching solution of Rongbao was extracted by centrifugation after immersion;The effective molluscacidal ingredients were explored via molluscacidal tests,neutralization tests and contrast tests.The histological changes of Oncomelania caused by those effective components of Rongbao were analyzed by continuous pathological section.Results:In the laboratory,by immersion in 50mg/L and 80mg/L of Rongbao for 5 days,the snail mortality were 70%and 100% respectively,while In the field experiment,the snail mortality were 81.29%and 94.59%respectively.By the spraying methods with 30g/m~2 Rongbao for 1 day,the snail mortality was 100%,and by the spraying and dusting methods with this dose for 7 days in the field,the snail mortality were 80.38%and 70.73%;24-hour leaching solution of Rongbao dosed 25,50,100,200mg/L for 72 hours,the snail mortality were 20%,85%,100%和100%separately;"1 to 5"-day leaching solution continuously of Rongbao with 200mg/L for 48 hours,the snail mortality were 100%,10%,5%,5%and 15%separately.There existed obvious absorption peaks at the wavelength of 200nm,205nm and 215nm for leaching solution of Rongbao.At the wavelength of 205nm, the OD for the neutralizer of Rongbao with 25,50,100mg/L were 0.021,0.070,0.172 respectively,while it for cyanamide dosed 6.25,12.5,25mg/L were 0.028,0.072,0.171 separately.And by immersion in these solutions for 48 hours,the snail mortality were 40%,95%,100%,20%,90%and 100%respectively;After treated with the leaching solution of Rongbao with 200mg/L,Tissue section reveals that epithelial cells of mantle destroyed,denudated,the basal layer of it bared and the number of secretory granules reduced.Article gill cells expanded, surfaces of which were burr-like,and he central vascular ruptured. Smooth muscle cells of proleg expanded,membrane fused and just liked glassy degeneration.Tepatic lobules atrophied and hepatic vessels expanded and ruptured,the number of secretory granules reduced significantly.Conclusion:Both immersion methods dosed 50mg/L and spraying methods dosed 30g/m~2 of Rongbao have potential molluscacidal effects. In field experiment,The molluscacidal effect by dusting methods of Rongbao was better that of spraying,different methods can be chosen according to different fields.Rongbao is a kind of slightly soluble substance.Effective molluscacidal component can be hydrolyzed and released in a short time.When the lixivium of Rongbao is isolated,the sediments left had no molluscacidal effect.So Rongbao has no character of slow releasing effect on molluscidal.Rongbao is a mixture containing mainly Calcium Cyanamide.It had been proved Spectrophotometry that molluscacidal component.But it still needs further research on whether the lixivium contains other component that impacts molluscacidal effect or not.In the molluscacidal effect of Rongbao lixivium,the mantle, branchial bar,abdominal foot and liver of the oncomelania had apparently Pathological changes.Especially,destroyed respiratory system and liver caused snail mortality directly.