| Aphis gossypii (Hemiptera:Aphididaethe) is one of the worldwide pests on cotton which can feed on many kinds of plants,such as Cucurbitaceae, Malvaceae, Solanaceae and Rutaceae.Especially for the cotton. Aphis gossypii can not only directly harm plants by feeding plants juices, but also can spread plant virus. And secretion of honey dew also affect the growth and development. Aphis gossypii can not be controled, except for by chemical method, in that they occurre by overlapping generations and in a large number.At present, chemical controlling method are widely used domestic and oversea. However, cotton aphid have development different level of resistance to organophosphates, carbamates, and pyrethroids, along with the wide and continuous use. Neonicotinoids pesiticides are widely used to control sucking mouthparts agricultural pests and sanitary insect pests, becoming the pesiticides which increase rapidly after pyrethroids. Because of the unique mode of action, Neonicotinoids pesiticides made a good effect on controlling the cotton aphids which have developed resistance to organophosphates, carbamates, and pyrethroids. Since put on the market in the90s, neonicotinoids pesiticides have become the first choice to control sucking mouthparts agricultural pests, including cotton aphids, and released the resistant problems. But with neonicotinoids pesiticides, including imidacloprid, used massively and unreasonably, the reisistance of cotton aphids are becoming more and more secious.In order to clarify the sensitive situation of cotton aphid populations in the field of Liaocheng, Tai’an and Dongying in Shandong province to the six kinds of neonicotinoid insecticides:imidacloprid, nitenpyram, acetamiprid, thamethoxam, thiacloprid, clothianidin, we did some research on the resistance of the cotton aphid populations, at the same time, synergism by enzyme inhibitors and test for activity of enzyme, aimed at clarifing the sensitive situation and the biochemical mechanism of cotton aphid populations in Shandong province, which can provide theory for reasonable use and put off the resistant problems. The results of the study are as follows:1. The resistance to six kinds of neonicotinoids pesiticides of the cotton aphids in Shandong provinceThe same aphid population developed different level resistance to six kinds of neonicotinoids pesiticides, however different aphid population developed different level resistance to the same kinds of neonicotinoids pesiticides. Field survey revealed that Tan’an aphid population developed a medium resistance to nitenpyram with resistance ratio of16.95and a low resistance to imidacloprid, acetamiprid with resistance ratio of5.69,9.57. Since the resistance ratio to clothianidin,thamethoxam and thiacloprid was less than3.0,Tan’an aphid population was still in a sensitive stage. Liaocheng aphid population developed a medium resistance to imidacloprid, acetamiprid and thamethoxam with resistance ratio of18.16-28.51and a low resistance to thiacloprid, clothianidin with resistance ratio of6.01,6.37, which was sensitive to nitenpyram. Dongying aphid population developed a medium resistance to imidacloprid, acetamiprid and clothianidin with resistance ratio of12.95-37.95and a low resistance to clothianidin, nitenpyram and thamethoxam with resistance ratio of7.07-4.75.2. Studies of the effect of Carboxylesterase inhibitor TPP, Glutathione-S-transferase inhibitor DEM and Mixed-functional oxidase inhibitor PBOThe effect of Carboxylesterase inhibitor TPP, Glutathione-S-transferase inhibitor DEM and Mixed-functional oxidase inhibitor PBO to six kinds of neonicotinoids pesiticides: imidacloprid, nitenpyram, acetamiprid, thamethoxam, thiacloprid, clothianidin were detected in the study. What’s more, we also test Carboxylesterase inhibitor TPP and Glutathione-S-transferase inhibitor DEM of Tan’an aphid population, Liaocheng aphid population and the sensitive aphid population. Mixed-functional oxidase inhibitor PBO had obvious synergism to imidacloprid, nitenpyram, acetamiprid, thamethoxam and clothianidin, while Carboxylesterase inhibitor TPP and Glutathione-S-transferase inhibitor DEM also had an effect. However, TPP had obvious synergism to thiacloprid as well as PBO and DEM playing a certain role. In conclude, Mixed-functional oxidase plays the main role, at the same time, Carboxylesterase and Glutathione-S-transferase play a certain role.3. The test of the enzyme activityThe enzyme activity test shows that, compared with the sensitive strain, Specific activity of Carboxylesterase of Tan’an aphid population and Liaocheng aphid population was2.38-fold and3.10-fold. And the Glutathione-S-transferase was1.36-fold and1.48-fold. We can see that Carboxylesterase and Glutathione-S-transferase play a certain role. |
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