Abstract
In our screening program for new agrochemicals from Chinese medicinal herbs, Murraya exotica was found to possess insecticidal activity against the maize weevil, Sitophilus zeamais and red flour beetle, Tribolium castaneum. The essential oil of aerial parts of M. exotica was obtained by hydrodistillation and investigated by GC and GC-MS. The main components of M. exotica essential oil were spathulenol (17.7%), α-pinene (13.3%), caryophyllene oxide (8.6%), and α-caryophyllene (7.3%). Essential oil of M. exotica possessed fumigant toxicity against S. zeamais and T. castaneum adults with LC50 values of 8.29 and 6.84 mg/L, respectively. The essential oils also show contact toxicity against S. zeamais and T. castaneum adults with LD50 values of 11.41 and 20.94 μg/adult, respectively.
Highlights
Sitophilus and Tribolium species are two of the major pests of stored grains and grain products in the tropics and subtropics [1]
A total of 36 components were identified in the essential oil of M. exotica, accounting for 99.5% of the total oil)
The essential oil was 12 times less toxic to the maize weevils and 4 times less toxic to the red flour beetles compared with the commercial fumigant methyl bromide (MeBr)
Summary
Sitophilus and Tribolium species are two of the major pests of stored grains and grain products in the tropics and subtropics [1]. Plant essential oils and their components have been shown to possess potential for development as new fumigants and they may have advantages over conventional fumigants in terms of low mammalian toxicity, rapid degradation and local availability [4]. Essential oils derived from more than 75 plant species have been evaluated for fumigant toxicity against stored product insects so far [5]. During our screening program for new agrochemicals from local wild plants and Chinese medicinal herbs, the essential oil from aerial parts of Murraya exotica L. have been found to possess insecticidal activity towards the maize weevil, Sitophilus zeamais (Motsch) and red flour beetle, Tribolium castaneum Herbst. No report on insecticidal activity of essential oil of M. exotica against stored product insects was available
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