Study On Pesticide Formulating Of Cantharidin Microemulsions

Cantharidin(C10H12O4)is an important natural product of terpinoids in the meloid insect (Meloidae). It is considered in the Chinese tradical medical science that meloids have good therapeutic effect upon antitumor and died tissue cleaning of wound ect.It was also reported that have activities against some pests and plant pathogenics. Being a precursor, cantharidin would play an important role in the research of selecting new kinds of insecticides and surmounting the formation and development of pest risistance to insecticides.According to the theories of composite membrane and R-ratio, the defined concentrations of DBS-Ca or 500# in the systems were 1 g, 5 g, 10 g or 15 g respectively, then the different non-ionic surfactants were added respectively. Scanning at the temperature range of 0~60℃, the eligible system should be transparent or semi transparent at certion point.After this system was adjusted by co-solvent or co-surfactant, the optimal system was selected finally.The micro-emulsion of cantharidin was obtained by providing an inert matrix composition comprising a defined mixture of a nonionic surfactant (DBS-Ca), both an anionic surfactant (emulsifier B) and another anionic surfactant (emulsifier F), mixing with the extract to form a micro-emulsion concentrate, and diluting with water .Preferably, the aqueous micro-emulsion includes methanol here in as a co-solvent in the micro-emulsion system.According to the related universal standard of pesticide, the quality indexes for 0.1 % cantharidin (ME) were established. It comprises appearance, content of cantharidin, PH value, cold stability, heat stability, and dillute stability and temperature range of transparence. The technic indexes of 0.1 % cantharidin (ME) were as follows:(1) The composition should appear as a single phase without any particulate or colloidal or a second phase being present when viewed by the naked eye.(2) The dispersion should remain clear and free of precipitation or flotage at the temperature range of-10~60℃.(3) The freeze-thaw test indicates that the frozen formulation could recover independently at the room temperature.(4) After heat storage at the temperature of 54±2℃,the decomposition rate of cantharidin should be lower than 8 %.The bioassay using the 3th instar of diamond back moth, Plutella xylostella L. showed that cantharidin micro-emulsion (ME) had obvious function of deterrent, poisonous action of contact and stomach digetion.The results of field trials showed that all instars of diamond back moth, Plutella xylostella L., could be effectively controlled by a 400 fold dilution of 0.1 % cantharidin. micro-emulsion (ME)As a competitive new product, the patent has been applied.