| Tea green leafhopper, Empoasca vitis G?the, is the most badly damaged pest in tea plantations in Chinese mainland and China's neighbouring countries, such as Vietnam and Burma. The pest has been mainly controlled by means of spraying pesticides during the past several decades. In 2009 the identification of the resistance of the pest against insecticides from Fujian Province showed the pest has developed a medium level of resistance to imidacloprid, and a high level of resistance to bifenthrin and acetamiprid. The colleagues in the tea industry speculate the amount of insecticides to control the leafhopper accounts for 40 % of the total amount of insecticides applied in the tea plantations per year. Additionally, the lavishment of pesticides usually occurs. The affairs of insecticide residue exceeding standard are difficult to avoid. It is imperative under the situation make a way of green controlling the leafhopper.The leafhoppers possess the significant habit to tend towards and feed on the tender shoots, for which the physical and chemical information emitting from tea shoots may be responsible. Furthermore, during summer and autumn seasons, the parasitic rate of eggs of the leafhoppers by the mymarid Stethynium empoascae Subba Rao was higher than the spring season, as the functional and numerical responses of the mymarids to the pest was quicker than in spring. The routine air entrainment was used to collect the volatiles among the tritrophic level: tea plant, leafhopper and mymarid. The Super Q was adsorbent, which was eluted by organic solvent after it adsorbing. The resulting extract was injected into GC-MS for qualitative and quantitative analysis. The activity of the volatiles were detected by bioassay so as to offer data for the development of entrapping preparation of the leafhopper and the attractant of the mymarid.The thirteen components in the volatiles of intact tea shoots were identified, i. e. (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-ethyl-1-hexanol, (E)-ocimene, linalool, nonanol, (Z)-butanoic acid, 3-hexenyl ester, decanal, tetradecane, caryophyllene, geraniol and hexadecane. In the laboratory the behaviour bioassay with Y-tube olfactometer results showed the attractivity of (E)-2-hexenal to the leafhopper was the strongest, followed by (E)-ocimene and linalool. However, the attractivity of blend 2, composed of (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-penten-1-ol, (E)-2-pentenal, pentanol, hexanol and1-penten-3-ol with the same concentration was stronger than (E)-2-hexenal. The blend 2 and (E)-2-hexenal loaded onto rubber nobs respectively to manufacture into lures, then attached on bud green sticky boards to make up traps. During the leafhopper population peak period, the traps were applied to entrap the leafhoppers. Two days later, the control efficacy of blend 2 and (E)-2-hexenal were respectively 59.3 % and 31.8%, with the control efficacy of the pure bud green sticky boards being 23.0%. Six days later, the control efficacy of blend 2 was 43.1%. The control efficacy of blend 2 excelled those of matrine and other botanical pesticides. In the laboratory, the differences in attractive activity of other twenty-one plant volatile components to the leafhopper were investigated by Y-tube olfactometer, in which pentanol,β-ionone, phenethyl alcohol, (+)-cedrol, (+)-3-caren and hexanol displayed the stronger attraction.Resorting to the same air entrainment methods, eighteen components were identificated from the volatiles of tea shoots, i. e. hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-2-hexen-1-ol, benzaldehyde, (Z)-3-hexenyl acetate, acetic acid, hexyl ester, (E)-ocimene, linalool oxide (Z)-furanoid, linalool, nonanol, phenylethyl alcohol, squalene, (Z)-butanoic acid, 3-hexenyl ester, pentadecane,α-farnesene,β–myrcene and hexadecane. It was detected that the content ofα-farnesene, benzaldehyde and (E)-2-hexenal augmented after the leafhopper damaging. Ten and eleven components were respectively identificated from the volatiles from the intact stems and leafhopper-damaged stems, i. e. (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-ethyl-1-hexanol, linalool oxide (Z)-furanoid, linalool, nonanol, tetradecane, pentadecane, hexadecane and (E)-2-hexenal, (Z)-3-hexen-1-ol, benzaldehyde, (Z)-3-hexenyl acetate, (E)-ocimene, linalool oxide (Z)-furanoid, linalool, squalene, (Z)-butanoic acid, 3-hexenyl ester, pentadecane,α-farnesene respectively. Compared with the volatiles of the intact stems, the content ofα-farnesene和benzaldehyde increased, whilst the content of (E)-2-hexenal, (Z)-3-hexen-1-ol and (Z)-3-hexenyl acetate decreased. The attraction of seven primary volatiles to the mymarid were detected by four-arm olfactometer, in which 10?4 g/mlα-farnesene display the strongest attraction, followed by benzaldehyde,(Z)-jasmone andβ-farnesene. On account of the results, the infochemicals, i. e.α-farnesene, benzaldehyde, (Z)-jasmone,β-farnesene, (E)-2-hexenal and methyl salicylate with the dosage of 10?2 g/ml and hexane, were chosen and manufactured into lures, subsequently, the lures were united with the coloured sticky boards to attract the mymarids in the plantations. The attractive efficacity of 10?2 g/mlα-farnesene was the best.In order to probe into whether the damages by tea green leafhopper and other important pests induce the same synomones, and enlarge the application scope of the synomones, we compared the composition of volatiles of tea shoots injured by tea green leafhopper, tea aphid, tea geometrid and cupmoth. Theα-farnesene, benzaldehyde and (E)-2-hexenal were common, especially the content of the former two was ample.On all accounts, we think that the certain kairomones exist in dense odours emitting from the fresh tea shoots, and the kairomones can regulate the behaviour of tea green leafhoppers. We can screen the key components and confect into the attractant in proper ratio for the mass trap of the leafhopper. The leafhopper damaging can induce the tea shoots to release the volatile synomones which attract the mymarids, and the synomones can be confected into the attractant which direct mymarids parasitize the leafhoppers so as to heighten the parasitic rates. The infochemicals can act as one of the main measures in green control system for the leafhopper. |
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