Study On Pesticides For Controlling Dialeurodes Citri Ashmead Y

In this paper, Dialeurodes citri Ashmead as the tested insects were collected from Guangxi Citrus Research Institute. Insecticidal activity of 13 chemical pesticides and 131 plant extracts to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory, in order to sift effective chemical and insecticidal plant against Dialeurodes citri Ashmead. On the basis of insecticidal activaty sifting, Pilea cavaleriei Levl. which had much higher insecticidal activaty to Dialeurodes citri Ashmead was siftted to be further investigated for active ingredients. And the extract was separated by liquid-liquid extraction and purified through column chromatograghy. Meanwhile, primary mechanism was investigated through the change of several enzymes.In order to define and compare the contact activities of different pesticides to Dialeurodes citri Ashmead, contact toxicities of 13 chemical pesticides to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that contact toxicity of 13 chemical pesticides to Dialeurodes citri Ashmead from the highest to lowest in proper order were acetamiprid, cyhalothrin, cypermethrin, methomyl, omethoate, thiamethoxam, deltamethrin, chlorpyrifos, fenpropathrin, imidacloprid, methidathion, thiacloprid and isocarbophos. Their LC50 were 1.7068, 3.7240, 3.7556, 4.5021, 5.4234, 7.1864, 10.7590, 11.3382, 11.3656, 12.8690, 19.1177, 23.2012 and 59.7984mg/mL. Acetamiprid of neonicotinoid insecticides had the highest contact toxicity to Dialeurodes citri Ashmead, while isocarbophos of organophosphate insecticide had the lowest contact toxicity, the former virulence was 34.04 times higher than the latter.126 species of plants belonging to 68 families collected from the northeast of Guangxi were extracted with methanol. Insecticidal activity of 131 plant extracts to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that at the concentration of 10mg/mL, most of the plant methanol extracts had higher contact activity to Dialeurodes citri Ashmead, of which with a corrected mortality of >80% after 48 hours were Pilea cavaleriei Levl., Artemisia carvifolia Buch.-Ham. ex Roxb., Pterolobium punctatum Hemsl., Cuscuta chinensis Lam., Buddleja asiatica Lour., Euchresta japonica Hook.f. ex Regel, Daphniphyllum oldhami (Hemsl.) Rosenth., Acacia confusa Merr., Sida rhombifolia L., Dendropanax macrocarpus C.N.Ho , Humulus scandens (Lour.) Merr. and Prunella vulgaris Linn.; with a corrected mortality ranging from 60% to 80% after 48 hours had 61 kinds , such as Clerodendron fortunatum L., Tetrastigma planicaule Gagnep., Gnetum montanum Markgr., Pyrrosia tonkinensis (Gies.) Ching, Phyllanthus urinaria Linn., Solanum verbascifolium L., Cryptotaenia japonica Hassk., Cibotium barometz (Linn.) J.Sm. and Piper puberulum (Benth.) Maxim.; corrected mortality of the other plants extracts were below 60% after 48 hours.In oder to further define and compare the contact activities of plant extracts, contact toxicities of 9 plant extracts to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that relative toxicities of 9 plant extracts from the highest to lowest in proper order were Pilea cavaleriei Levl., Prunella vulgaris Linn., Artemisia carvifolia Buch.-Ham. ex Roxb., Dendropanax macrocarpus C.N.Ho, Sida rhombifolia L., Acacia confusa Merr. Euchresta japonica Hook.f. ex Regel, Pterolobium punctatum Hemsl. and Cuscuta chinensis Lam.. Their LC50 were 1.3967, 2.0863, 2.2986, 2.3584, 2.8588, 3.4964, 3.6924, 4.1307 and 4.1626mg/mL. Pilea cavaleriei Levl. had the highest contact toxicity, while Cuscuta chinensis Lam. had the lowest contact toxicity, the former virulence was 1.98 times higher than the latter.According to above results, Pilea cavaleriei Levl. was selected for further study. The methanol extract of Pilea cavaleriei Levl. was preliminarily separated into 4 parts by liquid-liquid extraction with petroleum ether extract, ethylacetate extract, n-butanol extract and water extract. The insecticidal activities of 4 parts extract to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that at the concentration of 5mg/mL, insecticidal activity of 4 parts extract from the highest to lowest in proper order were petroleum ether extract, ethylacetate extract, n-butanol extract and water extract. Their corrected mortality were 62.71%, 19.11%, 18.01% and 11.45% after 48 hours. Petroleum ether extract had the highest contact toxicity, while water extract had the lowest contact toxicity. This indicates that the active ingredients of the methanol extract of Pilea cavaleriei Levl. mainly exist in the petroleum ether extract. It is a low-polar substances.By silica gel column chromatograghy and tested by TLC analysis, using chloroform/acetone as eluting solvent system, the petroleum ether extracts was separated into 17 groups. The contact toxicity of 17 groups to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that at the concentration of 2.5mg/mL, the insecticidal activity of groups 6, 8, 9, 10, 11 had higher than that of the others. Their corrected mortality were 70.73%, 66.47%, 65.28%, 62.10% and 67.73% after 48h; The corrected mortality of other groups had less than 40% after 48h.Groups 6, 8, 9, 10, 11 which had higher insecticidal activity to Dialeurodes citri Ashmead were selected to continue further to silica gel column chromatography, using chloroform/acetone as eluting solvent system, it was separated into 9 groups by TLC analysis. The contact toxicity of 9 groups to Dialeurodes citri Ashmead were determined by the using of the method of dipping leaf in laboratory. Results showed that at the concentration of 1.25mg/mL, the insecticidal activity of groups 7 had higher than that of the others,its corrected mortality was 50.49% after 48h, the corrected mortality of other groups had less than 20% after 48h.Influence of the methanol extracts of Pilea cavaleriei Levl. on protein content and 2 kinds of enzymes of Dialeurodes citri Ashmead was studied. After the treatment of the methanol extract of Pilea cavaleriei Levl., the content of protein declined, the activity of GSTS rised, while the activity of AchE could not be inhibited.