Studies On The Activity Of Chemical And Biological Insecticides Against Sweet Potato Whitefly And Aphids On The Protected Vegetables

Recently the Sweet Potato Whitefly (Bemisia tabaci(Gennadius)) and Aphids(Aphis gossypii(Glouer) and Myzus persicae(Sulzer)) are considered as one of the most serious pests on the protected vegetables in most regions of China. And they have caused severe damage to agriculture productions. The management in the cropping systems has been largely dependent on insecticides. Consequently, it is necessary to determine the toxicity of conventional insecticides (organophosphates, pyrethroids, cyclodienes), neonicotinoids, IGRs, bio- pesticide, etc. so as to provide scientific basis for the better control of them in the production of non-pollution vegetables and green vegetables.After treating for 24h and 48h, the toxicity of 13 insecticides on the adults of B. tabaci collected from the trial field of Nanjing Agricultural University was determined by leaf-dipping method. The results showed that matrine, avermectin, azadirachtin, endosulfan, emamestin benzoate, acetamiprid,high penetration imidacloprid, fipronil, pymtrozine had relatively high activity against the adult of B. tabaci, while the toxicity of chlorpyrifos, bifenthrin, imidaclopid, thiamethoxam was lower than others. The self-made insecticide 0.2% pymtrozine emulsifiable concentrate had good activity against B. tabaci in 72h, and LC50 value was 28.10 a.i. mg/L, indicating that pymtrozine had the potential for developing new because of its unique mode of action.The efficacy of the systematic action of imidacloprid and acetamiprid on the adult B. tabaci was compared through drenching cucumber and cotton seedling with 1/10 pot volume solutions containing 250, 500 a.i. mg/L imidcloprid and acetamiprid, respectively. And the similar results were achieved in both plants. At the beginning of the experiment, acetamiprid showed a relatively strong effect against the adult, with the time going, the twoinsecticides appeared the similar efficacy, and at the end of the experiment the residual activity of imidacloprid was higher than that of acetamiprid. The residual activity of imidacloprid could maintain more than 40days after drenching.The toxicity and efficacy of IGRs (buprofezin and pyriproxyfen) to the nymphs and eggs of B.tabaci reared with cotton were examined through both leaf-dipping method and dipping method. The effectiveness of buprofezin to the 1st instar and 4th instar nymphs of B. tabaci was observed, LC50 values were 1.334 and 128.8 a.i. mg/L, respectively. The difference in LC50 between the first instar and fourth instar nymph was 96.6 folds. The effect of pyriproxyfen on the emergence of 4th-instar B. tabaci with 0.0078-16.0 a.i. mg/L was observed almostly with no suppression when compared with that of control.The toxicity of pyriproxyfen on the 0-1 d old eggs of B. tabaci was observed through leafing dipping method and dipping method. The results showed that LC50 values were 0.0227, 0.0011 a.i. mg/L, respectively. The cotton leaves infested with eggs of different ages were dipped in 0.5, 5.0 a.i. mg/L, respectively, the results showed that 0-1, 1-2, 2-3 d old eggs were susceptible and the older ones were almost not affected by pyriproxyfen. When B. tabaci female were exposed to cotton plant treated with 10 a.i. mg/L pyriproxyfen for 48h, eggs oviposited during this period were not viable. And eggs hatching continued to be totally suppressed for an additional 96h(2-6 day) after the" transfer of the female to untreated leaves. The viability was reduced considerably for 0-6d old eggs by pyriproxyfen, while 6-8d old eggs were not affected.The toxicity of conventional chemical insecticides (imidacloprid, acetamiprid, fipronil, avermectin) and biopesticides(matrine, azadirachtin) to control A. gossypii and M. persicae was tested in the laboratory using leaf-dipping method and dipping method. The results showed that all of supplied insecticides had good effect on these two aphids. And matrine was proved to be the significant positive effects of temperature, while azadirachtin was tendency negative effect. The toxicity difference of matrine was 19.6 folds between 19℃...