Contact toxicity and persistence of essential oils from Foeniculum vulgare, Teucrium polium and Satureja hortensis against Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae) adults

Contact toxicity and persistence of essential oils extracted from Foeniculum vulgare Miller (Apiaceae), Teucrium polium L. (Lamiaceae) and Satureja hortensis L. (Lamiaceae) were evaluated against the adults of cowpea seed beetle, Callosobruchus maculatus (Fabricius) at 28 +/- 2 degrees C, 60 +/- 5% r.h. in dark conditions. Contact toxicity tests were conducted on one-day old adults of C. maculatus with 6 concentrations of essential oils at 24-h exposure time. The persistence of insecticidal activity of essential oils was examined for a period of 30 h at the LC99 level. The results indicated that mortality of adults was dose related. Males were more susceptible to essential oils than females. The essential oil of F. vulgare was the most toxic to male and female adults of C. maculatus with LC50 values of 390.38 and 513.46 mu l.m(-2), respectively. Moreover, S. hortensis oil was more toxic to male and female adults of C. maculatus with LC50 values of 535.69 and 640.99 mu l.m(-2) than T. polium oil with LC50 values of 1263.09 and 1469.72 mu l.m(-2), respectively. The results of persistence tests revealed that essential oil of S. hortensis was the most persistent, while that of T. polium was the least. High persistence of S. hortensis oil could be attributed to its high proportion of oxygenated compounds compared to other oils. The present study demonstrated that these essential oils can be used as appropriate alternative to control of cowpea seed beetle.