| Aphis gossypii Glover is the major pest of agricultural and distributes in all the world. Many crops, vegetables and fruit trees are harmed and various plant viruses can be spread by A.gossypii. Chemical control is widely used to manage A.gossypii and organophosphorus insecticides are one of the most important insecticides to control A.gossypii in agricultural production. However, Acetylcholinesterase is the target enzyme of organophosphorus insecticide and carbamateinsecticide. It was reported that the sensitivity of insects to insecticides could be affected by host plants. So in this paper the toxicities of some insecticides to A.gossypii were measured, and the effects of 3 OP insecticides to AChE in A.gossypii fed by four host plants were determined. The results were showed.The dipping leaves method was used to measured the toxicities of insecticides to A.gossypii. The results showed that A.gossypii was most pronounced to imidacloprid in the tested insecticides and LC50 was 4.203 mg/L. The values of LC50 of omethoate, phoxin and triazophos were 21.70,38.86,43.30 and 255.0 mg/L. The toxicity of five insecticides to A.gossypii is: imidacloprid < omethoate < phoxin < triazophos < cyhalothrin.There were significant differences in the AChE specific activities of A.gossypii fed by different host plants. The AChE specific activity of A.gossypii fed by cucumber was 38.8 nmol·min-1·mg-1, and fed by eggplant was 38.6 nmol·min-1·mg-1. There was no significant difference between them. The AChE specific activity of A.gossypii fed by rape was 36.6 nmol·min-1·mg-1. The AChE specific activity of A.gossypii fed by pumpkin was 35.1nmol·min-1·mg-1. The Km of AChE from A.gossypii fed by pumpkin was the smallest, the value was 0.259 mmol/L, and there was significant difference between pumpkin and three other plants. The values of the Vmax of AChE from A.gossypii had no significant differences between different host plants.It was revealed that AChE activities from A.gossypii fed by different host plants could be inhibited by Eserine and three tested OP insecticides at different concentrations. Inhibitory concentration of AChE activity from A.gossypii fed by four host plants by eserine has significant differences, the value of inhibitory concentration of AChE activity from A.gossypii fed by eggplant is 0.010 mmol/L, while fed by rape is 0.023 mmol/L. Inhibitory concentration of AChE activity from A.gossypii fed by four host plants by omethoate has no significant difference, the value of inhibitory concentration of AChE activity from A.gossypii fed by rape is 0.069 mmol/L, and fed by pumpkin is 0.148 mmol/L. Inhibitory concentration of AChE activity from A.gossypii fed by pumpkin,eggplant and rape by triazophos has no significant difference. Inhibitory concentration of AChE activity from A.gossypii fed by cucumber and rape by phoxin has no significant difference, Inhibitory concentration of AChE activity from A.gossypii fed by pumpkin and eggplant by phoxin has no significant difference.It was proved that three tested OP insecticides could inhibit the activity of AChE in A. gossypii significantly, and their inhibition abilities increased with time. The values of I50 of omethoate to the AChE from A.gossypii fed by four host plants had significant difference, The values of I50 of omethoate to the AChE from A.gossypii fed by eggplant was 4.27 min,and the values of I50 of omethoate to the AChE from A.gossypii fed by rape was 5.05 min.The values of I50 of phoxin to the AChE from A.gossypii fed by cucumber, pumpkin and rape had no significant difference, The values of I50 of phoxin to the AChE from A.gossypii fed by eggplant was 4.67 min,and the values of I50 of phoxin to the AChE from A.gossypii fed by rape was 5.69 min.The values of I50 of triazophos to the AChE from A.gossypii fed by cucumber was 4.27 min,and the values of I50 of triazophos to the AChE from A.gossypii fed by eggplant was 6.88 min. |
