Seasonal changes in yield, composition and fumigant action of essential oil of Murraya koenigii L. against Rhyzopertha dominica(F.) and Sitophilus oryzae (L.)Pantnagar Journal of Research, Volume - 19, Issue - 2 ( May-August, 2021)
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Experiments were conducted to study the variation in the yield and composition of essential oil of Murraya koenigii and its effect on fumigant action against Rhyzopertha dominica and Sitophilus oryzae. The essential oil was extracted from the leaf of test plant in each month of the year and its composition was determined through Gas Chromatography-Mass Spectrometry. The samples of spring (March-April), summer (May-June), rainy (July-September), autumn (October-November) and winter (December- February) were pooled to study the effect on test insects. The yield of essential oil varied from 0.07-0.43% in different month and maximum oil was obtained in November and December. The amount of monoterpenes was higher in autumn season (61.60%) followed by summer (59.00%), spring (55.80%), winter (55.41%) and rainy season (43.37%). On the other hand, sesquiterpenes were higher in spring season (36.46%) followed by winter (30.28%), autumn (28.55%),summer (26.60%) and rainy season(24.73%). Total terpenes were highest in spring (92.25%) followed by autumn (90.15%), winter (85.69%), summer (85.60%) and rainy season (68.10%). The essential oils of all the seasons inhibited 97.8 to 100.0 per cent progeny production at higher concentrations of 0.20 and 0.10% (w/v).At lower concentrations of 0.05, 0.025 and 0.012%, oils extracted in spring season was most effective against R. dominica and S. oryzae, while lowest efficacy was shown by oil extracted in rainy season. Results demonstrated that the efficacy of oil was dependent on level of constituents which varied with stage of plant and season.
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