The Effect Of Neonicotinoid Insecticide Imidacloprid On Physiology And Biochemistry Of Silkworm,Bombyx Mori L.

Imidacloprid is a kind of neonicotinoid insecticide and widely applied in the control of agricultural and forest pests.In this study,the model of chronic poisoning on silkworm is established with imidacloprid as the representative agent.Based on the model,the influences of chronic poisoning imidacloprid on growth and development and food utilization of the larvae,the characteristics of metabolism and distribution of trace imidacloprid in silkworm tissue and the activity of related detoxification enzymes,glutathione synthase are studied.The obtained results are as following.1.The silkworm exhibites the following symptoms,such as antifeedant,twisting into "C" or "S" type,vomiting brown intestinal juice,shortening softening of the body and so on.The 96h-LC50 of newly molted 3rd instar larvae is 1.177 09 mg/L,and the 5rd instar larvae is 1.726 01mg/L.The concentrations of the imidacloprid of the chronic poisoning symptoms of silkworm in the experiment are10-1,10-2,10-3,10-4,10-5 mg/L,respectively.2.Mulberry leaves treated with different concentrationsof imidaclopridwere are fed to the silkworm larvae,the effects of imidacloprid chronic poisoning to growth and development and food utilization of the larvae are studied by gravimetric method.High concentrations of imidacloprid(10-1 and 10-2 mg/L)significantly inhibited the growth and development and food utilization of the silkworm;On the contrary,low concentrations of imidacloprid(10-3,10-4 and 10-5 mg/L)have auxo-action to the growth and development and food utilization of the silkworm.3.Mulberry leaves treated with different concentrations of imidaclopridwere are fed to the silkworm larvae,with the effects of imidacloprid chronic poisoning to economic characters of the larvae by gravimetric method and statistical method.The results show that imidacloprid have significantly influences on silkworm larvae death status,percentage of pupation,cocoon shell weight,cocoon shell rate,and the rate of dead worm;The higher the dosage of imidacloprid,the more obvious the toxicity to the silkworm.The effects of each liquid drug group on the quality of matured silkworm,whole cocoon weight and pupal weight are different,low concentration imidacloprid could promote it,while high concentration inhibited it.4.The effects of imidacloprid on digestive enzymes(amylase,sucrase and trehalase)activities of the 5th instar larvae are studied by gravimetric method and measuring enzyme activities.The results show that the amylase and trehalase activities in the midgut of the 5th instar larvae treated with low concentrations of imidacloprid promote significantly,whereas those treated with high concentrations of imidacloprid decrease significantly at 1~5 d of 5th instar larvae,and then recovere to the same as or a higher level than the control.The sucrose activity in the midgut of the larvae treated with imidacloprid is inhibited,and a positive correlation between concentrations and inhibitory action is shown.5.The contents of imidacloprid in midgut,blood,fat body and silk gland of 5th instar larvae at different times are determined by HPLC.The results show that the reaching order of imidacloprid to the tissues of silkworm is midgut,blood,fat body,and silk gland,and the midgut and silk gland have a cumulative effect on imidacloprid pesticides.6.The influence on imidacloprid to the activity of GSTs of 5th instar larvae are studied by measuring enzyme activity.The results showed that imidacloprid solution has different effects on GSTs enzyme activity in different tissues of silkworm,and GSTs activity in blood and fat bodies is inhibited temporarily and then induced,in midgut is inhibited,and there is no significant effect in silk gland.