Sublethal Effects Of Thialoprid And Clothianidin On Silkworm,Bombyx Mori L.

At present,the researches on the pesticides toxicity to silkworm are mainly focuses on the acute toxicity,but barely about the sub-lethal effect caused by trace pesticides.In tihs research,Two nicotine pesticides Thiacloprid and Clothianidin were selected to treat mulberry leaves with sublethal concentration gradient according to the acute toxicity test results.The sublethal effects of Thiacloprid and Clothianidin on silkworm were investigated by feeding the silkworm larve from 2nd instar to the 5th instar continuously and investigating the influences of Thiacloprid and Clothianidin on developmental duration of silkworm larvae,mass of molting silkworm,Feed efficiency of silkworm,the death rate and pupation rate of silkworm,the economic traits change of silkworm.The study obtained the following results:1.In this study,the acute toxicity of Thiacloprid and Clothianidin to silkworm was accomplish by immersion method.The results showed that the 96 h LC50 of Thiacloprid was 0.235 mg/L on the 2nd instar silkworm,and the 96-h LC50 of Clothianidin is 0.076 mg/L for the 2nd instar of silkworm.According to the toxicity evaluation criteria,both of them belong to highly toxic pesticides to silkworm.It is suggested that the application of Thiacloprid and in mulberry garden and its surrounding areas should be prohibited2.The effects of Thiacloprid and Clothianidin on the developmental duration of silkworm were as follows:the developmental duration of silkworm in high concentration group was prolonged compared with that in control group;the developmental duration of silkworm in medium concentration group was less different from that in control group;the development of silkworm in low concentration group was shortened compared with that in control group.At the same concentration,the effects of Thiacloprid and Clothianidin on the developmental duration of silkworm increased with the growth of silkworm instars.3.The effects to the mass of molting silkworm on Thiacloprid and Clothianidin are as follows:the mass of molting silkworm in high concentration group is lower than that in control group,and the body weight of silkworm in low concentration group is higher than that in control group.At the same pesticide concentration,the influence on the mass of molting silkworm on Thiacloprid and Clothianidin increased with instars.4.The effects of Thiacloprid and Clothianidin on the feed efficiency of silkworm were as follows:the silkworm feed efficiency,digestibility,cocoon conversion efficiency decreased at high concentration,while the silkworm feed efficiency,digestibility,cocoon conversion efficiency increased at lower concentration5.The effects of Thiacloprid and Clothianidin on the economic traits of silkworm were as follows:the cocoon weight,cocoon layer weight and cocoon layer rate of high concentration group decreased,while the cocoon weight,cocoon layer weight and cocoon layer rate of low concentration group increased6.The sublethal effects of Thiacloprid and Clothianidin on silkworm were as follows:when the physical concentration of Thiacloprid and Clothianidin is higher,it inhibited the growth and development,feeding and digestion,and economic characteristics of silkworm,and at lower concentration,it promoted the growth and development,feeding and digestion,and economic characteristics of silkworm.