Preliminary Study On The Effects Of Dimethoate On The Growth, Development And Reproduction Of Antheraea Pernyi

Chinese oak silkworm,Antheraea pernyi,is a characteristic economic insect originated from China,and mainly distributed in Liaoning,Jilin,Hebei and Shandong provinces.This wild silkworm cocoon production in Liaoning province account for 70% in China.Chinese oak silkworm rearing has become the mainly incomes of local farmers in mountain areas,and has a great contribution to county economy.The Blepharipa tibialis Chao is a parasitic pest that seriously endangers the spring silkworm rearing.Since 1960 s,dimethoate has been used as the main medicine to control the B.tibialis.After dimethoate has been used a certain number of years,increased resistance in B.tibialis in tussah silkworm nursery.The working solution concentration of dimethoate keeps growing in tussah rearing.Farmers always lose money because of wrong using this drug.In order to reduce the concentration of dimethoate and ensure the safety of drug using,dimethoate and synergetic compound were used to control B.tibialis in recent years.Till now,the physiological and biochemical effects of high dose dimethoxide,dimethoxide and synergetic compound on A.pernyi have not been reported.In view of this,this study selects "Preliminary study on the effects of dimethoate on the growth,development and reproduction of Antheraea pernyi" as the topic,which is guidance to drug using in tussah rearing.This research adopts the combination of indoor test and outdoor test.The toxicity of dimethoate was test to the fifth instar A.pernyi larvae by leaf diping method.From lowest test concentration?practical application?to highest concentration(LC₂₀),four concentrations were carried out in outdoor experiment?L₁,L₂,L₃ and L₄ represent 4 dimethoate concentrations,LZ₁,LZ₂,LZ₃,and LZ₄ represent 4 dimethoate and synergetic compound concentrations?.Growth and development of A.pernyi were investigated in outdoor rearing.The influence of drug treatment has been investigated in every stage of silkworm,including larva,pupa and adult.Several detoxification enzymes and acetylcholinesterase activities under dimethoate treatment haven been studied.The results are as follows:1.From the results two drugs treatment,both of them have great influence on growth and reproduction in A.pernyi.Different concentrations of the two drugs can reduce weight in spring tussah rearing.Higher drugs concentraions,smaller larvae will get compare with control.Larval period will increase under higher drug concentrations.For example,L₃,L₄,LZ₃,and LZ₄ have longer larval period than control.The L₁,L₂ have longer pupae period in female,and L₁,L₂,L₃,and LZ₃ larvae have longer pupae period in male.The cocoon formation rate and cocoon layer rate of spring silkworm decreased with the increasing drug concentration.The cocoon formation rate of L₃,L₄ and LZ₄ was significantly lower than control;and the cocoon layer rate of L₃,L₄ and all LZ treatments were significantly lower.The rate of pupation of spring silkworm treated by L₁,L₂ and LZ₁ was significantly lower than that of control.The pupa weight and pupa length of spring silkworm have no influence.In spring,the female-male ratio was significantly lower except L₂ and LZ₁.There was no significant difference in female-male ratio of autumn silkworm rearing.The spring pupae eclosion rate and male adult insect life span were similar to control group after drug treatment.Female adult LZ₄ has shorter life time than control.With the increasing drug concentration,the spawning amount of spring silkworm decreasing,and L₃,L₄,LZ₂,LZ₃ and LZ₄ treatments were significantly lower than control.Drug treatment had no effect on the hatching rate adult survival of spring silkworm.There was no different influence between dimethoate,dimethoate and synergetic compound treatment of the same concentration.In addition,the drug treatment will cause part of the spring silkworm pupation deformity.2.The P450 activity of fat body,haemolymph and head was significantly increased after dimethoate treatment.It reached the maximum value at 12 h in fat body and haemolymph,and reached the maximum value at 6 h in head.GST activity in fat body increased at 6 h and 12 h,and 3 h is the highest expression after dimethoate treatment,while up-regulated at 12 h,24 h of haemolymph,and peaked at 24 h.GST expressed in head and highest at 12 h after treatment.Car E activity increased significantly at 6 h and 12 h in fat body.ACh E activity in fat body was significantly increased at 12 h after the treatment,and ACh E activity in haemolymph was significantly increased at each sampling time point during the treatment,and reached the maximum value at 6 h after the treatment.ACh E activity in the head was significantly increased at 3 h,6 h and 12 h after the treatment,and reached the maximum value at 6 h after the treatment.It can be seen from the results that the compound treatment of dimethoate,dimethoate and synergistic agent has a negative effect on the growth and reproduction of A.pernyi,and high concentration has a greater effect.There was no more additional influence of compound compared with only dimethoate to A.pernyi.In summary,silkworm rearing farmers need strictly control dimethoate dosage,and the maximum concentration should not exceed 2.88 g/L.Under the control B.tibialis,we also need make sure prevent negative influence on A.pernyi.