Effect of Citrus limonum essential oil against granary weevil, Sitophilus granarius and its chemical composition, biological activities and energy reserves

Abstract

Stored grains could lose substantially their nutritional quality, and consequently its value, between storage and consummation because of insect’s infestation. One of the most frequent pests of wheat is the grain weevil (Sitophilus granarius L.). Cleverly hidden, the immature stages of this destructive pest are very difficult to identify. Protecting stored grains has become an agricultural challenge. In the present study, the essential oil (EO) distillated from Citrus limonum (L.) (Burm. F., 1768) and analyzed by gas chromatography-mass spectrometry (GC-MS) revealed the presence of 47 compounds with (Z)-citral (30.74%), dl-limonene (19.81%) and geranyl propionate (16.28%) as major components. In a second series of experiment, its fumigant (using filter paper), repellent (by semi circles joined discs) and residual (persistent insecticidal activity) activities were examined against Sitophilus granarius (L.) adults. The total nutrition (carbohydrates and lipids) depletion index (NDI) was also calculated. Residual toxicity and repellency of EO were demonstrated after fumigation against S. granarius with a dose-response relationship. The effectiveness of EO was exposure time dependent and its residual activity persisted up to 30 h following mortality. Moreover, data showed that treatment of S. granarius adults had adverse effects on the depletion of their energy reserves. C. limonum EO declined the lipid and carbohydrate contents in adults. Obtained data prove that botanical essential oils could be considered as potent biorational alternatives to synthetic insecticides for pest control of stored products in a sustainable manner.