Insecticidal Properties and Chemical Composition of Conyza Aegyptiaca (L.) Oil: Studies on Two Dipterous Insect Pests

The herb, Conyza aegyptiaca L., was subjected to hydrodistillation process to extract the essential oil from the whole dry plant material. Larvae and adult stages of the mosquito, Anopheles pharoensis, and the housefly, Musca domestica, were used as test model organisms representing two dipterous insect pests of medical importance. Under standard bioassay test methods, the LC50 of the oil accounted to 37.8 ppm and 0.087 mg/cm against larvae and adults of An. pharoensis, respectively. These toxicity parameters were found to be 71.8 ppm as LC50 and 0.125 μg/insect as LD50 against larvae and adults of M. domestica, respectively. Using GC/MS analysis, we identified 19 compounds constituting ca. 97% of phytochemicals present in the oil, such as monoterpenes, sesquiterpenes and esters. Limonene constituted about 50% of the plant oil (48.79%), followed by (E) β-Ocimene (8.66%), Germacrene D (7.54%) and β-pinene (6.91%). The occurrence of the other constituents ranged between 0.27% and 5.29%. It was concluded that the potency of C. aegyptiaca oil refers mainly to the presence of limonene. The findings of this study may encourage more research aiming at investigation of eco-friendly biopesticides based on botanical resources.