Toxicity And Sublethal Effects Of Neonicotinic Insecticides On Riptortus Pedestris

Riptortus pedestris is concentrated in East Asia and Southeast Asia.In recent years,the damage to soybean-based leguminous crops in various regions of my country has increased year by year.As one of the main pests of soybean,it can damage the flowers and branches,prolong the growth period,and can also suck the pods to form black spots.In severe cases,the whole plant will collapse and the seeds will not harvest,which is the so-called"symptomatic green"of soybeans.At present,the prevention and control of the R.pedestris mainly relies on chemical control,which leads to the increase of resistance of the R.pedestris to a variety of control agents year by year.The sublethal effects of the control agents and the changes in the activity of detoxification enzymes in the body may be related to the rapid development of the population.Based on this,this study preliminarily clarified the indoor toxicity of five neonicotinoid insecticides and the effects of sublethal doses of the tested agents on the growth and population reproductive ability of the R.pedestris.The main research results are as follows:1.The LC₅₀ of five neonicotinoid insecticides on the 1^st instar nymphs of R.pedestris nymphs were acetamiprid 3.32 mg/L,dinotefuran 5.43 mg/L,imidacloprid 6.29 mg/L,thiamethoxam 15.16 mg/L,and nitenpyram 17.56.mg/L.The LC₅₀ of the five neonicotinoid insecticides on the 2^nd instar nymphs of R.pedestris nymphs were dinotefuran 14.98 mg/L,imidacloprid 21.10 mg/L,thiamethoxam 24.68 mg/L,nitenpyram 33.54 mg/L,and acetamiprid 38.92 mg/L.Acetamiprid and dinotefuran showed higher toxicity to the 1^st and2^nd instar nymphs of R.pedestris,respectively.2.Sublethal effects of acetamiprid and dinotefuran on the 1^st instar nymphs of R.pedestris:after the treatment of sublethal dose of acetamiprid on the 1^st instar nymphs of R.pedestris,the development period of the 3^rd instar nymph is 6.3 days,which is significantly longer than Control,while no significant difference was found in the 4^th and 5^th instar nymphs.After the treatment of sublethal dose of dinotefuran on the 1^st instar nymphs of R.pedestris,the development period of the 3^rd,4^th and 5^th instar nymphs were prolonged significantly.After the treatment of sublethal doses of acetamiprid and dinotefuran,no significant difference was found in the emergence rates and longevity of adults,but the pre-oviposition period was prolonged and the weight of males decreased compared to control.3.The effects of acetamiprid and dinotefuran on detoxification enzymes in 1^st instar nymphs of R.pedestris:no significant difference was found in the activities of carboxylesterase,multifunctional oxidase,and glutathione transferase between the treatment of acetamiprid and control,but the activity of UGTs increased;no significant difference was found in the activities of UGTs glycosyltransferase,multifunctional oxidase,and glutathione transferase between the treatment of acetamiprid and control,but the activity of carboxylesterase increased.