Fumigant and repellent potentials of Ricinus communis and Mentha pulegium essential oils against Tribolium castaneum and Lasioderma serricorne

This work was aimed to investigate the chemical composition of pennyroyal (Mentha pulegium L.) aerial parts and castor (Ricinus communis L.) stems essential oils from Tunisia. Fumigant and repellent toxicities were assessed toward two major stored product beetles: Lasioderma serricorne and Tribolium castaneum. Pennyroyal essential oil was characterized by a clear predominance of the oxygenated monoterpenes fraction (97.10%) instead of phenol fraction (61.47%) in the castor essential oil. The major common compounds of Mentha pulegium were pulegone and isomenthone, whereas 2,4-bis (dimethylbenzyl)-6-t-butylphenol was the main volatile compound of castor essential oil. Pennyroyal essential oil showed a strong antiradical capacity (IC50=14 mu g/mL) which is higher than synthetic standard. The effectiveness of pennyroyal essential oil against the coleopteran insects showed potential fumigant impact particularly against Lasioderma serricorne with LC50=8.46 mu L/L air. Moreover, significant pest repellent activity was demonstrated with Ricinus communis and Mentha pulegium where the repellency effects reached 80 and 60% after 1 and 24h of exposure against Tribolium castaneum at doses of 0.31 mu L/cm(2) and 0.078 mu L/cm(2) respectively. Hence, these findings underlined the potential insecticidal effect of castor and pennyroyal essential oils and highlighted their use as valuable food and insecticide products instead of synthetic pesticides.