Repellency and toxicity of essential oils from two aromatic and medicinal plants and their components against bean beetle, Callosobruchus maculatus (F) (Coleoptera: Chrysomelidae: Bruchinae)

Essential oils (EOs) from two species of medicinal plant growing in Iran (M. piperita and C. cyminium) were first analyzed by gas chromatography (GC) and GC/mass spectrometry (MS) and then evaluated for toxicity and repellent activity against Callosobruchus maculatus. The fumigant toxicity of the volatile oils was tested against ۱week old adults of C. maculatus at ۲۸ ± ۲ C and ۶۵ ± ۵% RH in darkness under laboratory conditions (۲۹±۱°C , ۶۰±۵% r. h.). The essential oil from Cuminium cyminium and Mentha piperita have a number of bioactive compounds and their chemical constituents were analyzed by GC-MS. Seventeen and fourteen components were identified in Mentha piperita and Cuminium cyminium respectively. The main components of the M. piperita oil were menthone (۲۲.۸%), menthol (۱۶%), isomenthone (۸.۱%), Pulegone (۸.۱%), ۱, ۸- Cineole (۵.۹۵%) and limonene (۵.۸۳%). The main components of the C. cyminum oil were α- Pinene (۲۸.۱۵%), γ- terpinene (۱۳%), Linalool (۱۰.۹%), ۱,۸- Cineole (۹.۸۵%), α- terpinene (۹.۲۵%) and γ- terpinene-۷-ol (۸%). with the different oil doses and various periods of time. Results showed that mortality of insects are increased by increasing concentration and the time of distillation. So that, after ۷۲ hours, the highest concentration of each plant oils tested, led to death of hundred percent of insects. According to the essential oil bioassays against adult’s insects, the levels of LC۵۰ and LC۹۵ were determined. In evaluate fumigant toxicity these values of C. cyminum and M. piperita oils were estimated respectively (۹۲.۴۶ and ۲۲۴.۵۳) μl/l air and (۵۴۹.۵۷ and ۱۱۷۳) μl/l air after ۴۸ h length of exposure and in contact toxicity these values of C. cyminum and M. piperita oils were estimated respectively (۰.۱۰۷ and ۰.۱۷) μl/insect and (۰.۱۲۲ and ۰.۴۲۶) μl/insect after ۴۸ h length of exposure. Also, percent repellency (PR) of essential oil from Cuminum cyminum and Mentha piperita against Callosobruchus maculatus were determined by treated filter paper test. Results showed that PR is increased by increasing concentration of oils and the oils showed high insecticidal and percent repellency properties against the adults of Callosobruchus maculatus (Fabricius). The results indicate that the essential oil of M. piperita and C. cyminium aerial parts and isolated compounds have potential for development into natural insecticides or repellents for control of insects in stored products.

Keywords:

Repellency , Toxicity , Plant essential oils composition , Pest stored-products , Iran