Study On Fumigation Activities Of Plant Essential Oil To Stored Grain Pest

This research extracted 8 plant essential oils by steam distillation and tested the fumigant toxic effects of 15 species of essential oils vapours on the adult of Sitophilus zeamais Motschulsky and Tribolium castaneum Herbst to select two better plant essential oils respectively.And then under different conditions(i.e.different concentration,adding foodstuff and different temperature) the fumigant toxic effects were studied.Finally fumigant activities of four monomers on the adult of S. zeamais and T.castaneum was tested.The result was as follow:1.Eight plant materials were extracted by steam distillation to get the oil water mixtures.The mixtures were extracted by the petroleum ether.The petroleum ether extracts were concentrated to get the maximum oils.Result showed that extract rate of the plant essential oils were low by steam distillation and the obtained extract rate presented important differences.The extract rates of only 2 species reached 1%,with a maximum for Illicium verum with 1.87%.The extract rates of the other 6 species were all under 1%,with a minimum for Capsicum annuum with 0.08%.2.The essential oils presented different fumigant activities on the adult of S. zeamais and T.castaneum.With the fumigant concentration of 14.7μL/L and 48h exposure time,eight plant essential oils had fumigant effects on S.zeamais and six plant essential oils had fumigant effects on T.castaneum.Mentha haplocalyx oil and Mentha spicata oil had better fumigant effects on S.zeamais.At 48h,lethality rate of M.haplocalyx oil had reached 100%mortality,and M.spicata oil values reached 79.17%.â… .verum oil and Alpinia officinarum oil had stronger fumigant effects on T. castaneum.At 48h,lethality rate of the two oils both reched 100%mortality.3.More results showed by the fumigant toxicity experiments.After 24h,48h and 72h,values of LC₅₀ of M.haplocalyx oil on S.zeamais were respectively 11.53μL/L,9.49μL/L and 7.93μL/L,and values of LC₅₀ of M.spicata oil on S. zeamais were respectively 13.43μL/L,11.36μL/L and 9.20μL/L.Values of LC₅₀ ofâ… . verum oil on T.castaneum were respectively 6.50μL/L,3.70μL/L and 3.31μL/L after 24h,48h and 72h,and values of LC₅₀ of A.officinarum oil on T.castaneum were respectively 10.42μL/L,9.18μL/L and 8.01μL/L.4.The four essential oils still had good fumigant effects on the testing insects after adding grain.With 70%grain loading degree and 7 days exposure time,values of LC₅₀ of M.haplocalyx oil and M.spicata oil on S.zeamais were 231.50μL/L and 268.71μL/L,and values of LC₅₀ ofâ… .verum oil and A.officinarum oil on T. castaneum were 273.10μL/L and 294.76μL/L.On the condition of same grain loading degree,the mortalities of testing insects increased with the concentrations of essential oils.When the grain loading degree was different,the fumigant concentrations increased with the amount of grain.Adsorption rate of wheat to essential oils were different.The bigger of space volume of wheat,the more adsorption to essential oil.5.With different temperature(10℃,18℃,27℃),at 24h,48h and 72h expoure periods,the values of LC₅₀ of four essential oils presented downtrend along with the increaseing of fumigant temperature,with the minimum value at 27℃.When the temperature is same,the values of LC₅₀ decreased with the longer of the exposure time.The four essential oils had best fumigant effects at 27℃72h exposure time.6.Fumigant activities of three compounds in M.haplocalyx oil and M.spicata oil on the adults of S.zeamais:carvone＞limonene＞menthol.After 24h exposure time,the correct mortalities of carvone with three fumigant concentrations had reached 100%.Two compounds inâ… .verum oil and A.officinarum oil,transanethole and limonene,had good fumigant effects on adults of T.castaneum.The correct mortalities of trans - anethole with three concentrations had reached 100%. So carvone,limonene and trans - anethole are effectively insecticidal activity component of fumigant.