Toxicities And Biochemical Mechanism Of Organophosphorus And Pyrethroid Insecticides On Aphis Sp.

Aphis sp. is one of the major pest of the wolfberry, and causes a horrible threat to the yield and quality of wolfberry in long-term. Some measures should be done to control Aphis sp. effectively, ensure the wolfberry production, improve the quality of the wolfberry and reduce pesticide residues. Organophosphorus and pyrethroid insecticides have always been used to control Aphis sp. In this paper the toxicities of three insecticides to Aphis sp. were measured, and biochemical mechanisms of the two kinds of insecticides to Aphis sp. were studied too.1. The toxicities of three common insecticides to Aphis sp. were studied. The toxicity of deltamethrin to Aphis sp. is the strongest among three tested insecticides, and LC50=24.979mg/L, while the LC50values of imidacloprid and omethoate were29.194,40.086mg/L. The slope of omethoate and deltamethrin were similar, and value of omethoate and deltamethrin was1.323,1.370. The slope of imidacloprid was different from them and it was1.146.2. It was studied that substrate specificity of acetylcholinesterase to Aphis sp. The results showed that the activity of AChE from Aphis sp. hydrolyzing ATCh was the highest, Vmax=13.412μmol/min·mg, while the affinity of AChE to BuTCh was the closest among the four substrates,Km=0.224μmol/L. The hydrolyzing tendencies of AChE from Aphis sp. hydrolyzing four substrates were similar.3. It was indicated that OP insecticides tested could inhibitor the activity of AChE in Aphis sp., and the sensitivity of AChE to omethoate was the highest among the three tested insecticides, and its I50value was6.9×10-6mol/L. The values of I50of phoxin and triazophos to AChE were9.8×10-6and11.8×10-6mol/L. The inhibitory curses of three insecticides to AChE were same,and their inhibition abilities increased with time. IT50of triazophos was6.54min and the IT50values of omethoate and phoxim were5.05and4.57min.4. The inhibition of five pyrethroid pesticides and endosufan to mitochondrial Na+-K+-ATPase and Ca2+-Mg2+-ATPase from Aphis sp. was determined. The results showed the inhibition of ATPase activity by five pyrethroids insecticides was increased with the increasing of insecticides concentrations from1×10-4to 1×10-8mol/L. Na+-K+-ATPase and Ca2+-Mg2+-ATPase could namely be inhibited in a certain degree. When the final concentration of five pyrethroid insecticides was1×10-4mol/L, the inhibition of five pyrethroids to Na+-K+-ATPase was higher than that of them to Ca2+-Mg2+-ATPase. The order of inhibition to Na+-K+-ATPase was cyfluthrin> bifenthrin>cypermethrin> fenpropathrin> deltamethrin in1×10-4mol/L, percentage of inhibition of Na+-K+-ATPase was55.12%,52.59%,47.60%,37.19%and35.36%. However it was different that inhibition of pyrethroids to Ca2+-Mg2+-ATPase from inhibition to Na+-K+-ATPase, and inhibition of bifenthrin to Ca2+-Mg2+-ATPase was the largest among the tested pyrethroids and the percentage of inhibition was46.41. On the contrary the inhibition of deltamethrin to Ca2+-Mg2+-ATPase was the smallest and the valve was32.36%. The inhibition of endosulfan to Na+-K+-ATPase and Ca2+-Mg2+-ATPase was smaller than that of tested pyrethroids, the percentage of inhibition to Na+-K+-ATPase was31.15%and to Ca2+-Mg2+-ATPase was30.79%.