Not just popular spices! Essential oils from Cuminum cyminum and Pimpinella anisum are toxic to insect pests and vectors without affecting non-target invertebrates

Each year the flavor and fragrance industry produces more than hundred thousand tons of essential oils. An important portion of this production might be directed to the fabrication of green pesticides relying on the well documented efficacy of many essential oils against insect pests as well as vectors, besides their safety for human health and the environment. In this regard, two popular spices of economic importance, such as cumin (Cuminum cyminum) and anise (Pimpinella anisum), which are not only cheap, readily available, generally recognized as safe (GRAS), but also produces larger amounts of essential oils, are gaining interest for botanical insecticide development. Herein, we evaluated the efficacy of the essential oils obtained from seeds of these two spices on two agricultural pests, i.e., the peach-potato aphid Myzus persicae and the tobacco cutworm Spodoptera hoorahs, and on two insect vectors, i.e., the common housefly Musca domestica and the lymphatic filariasis and Zika virus vector Culex quinquefasciatus. Furthermore, their safety on beneficial organisms such as the earthworm Eisenia fetida and the aphid predator Harmonia axyridis was assessed. The two essential oils, characterized by alpha-terpinen-7-al (35.3%), cumin aldehyde (21.8%), and alpha-terpinen-7-al (15.4%), and (E)-anethole (93.0%), respectively, showed noteworthy effects against all pest targets, with anise more effective on larvae of C. quinquefasciatus (LC50 = 25.4 mu l L-1) and S. hoorahs (LD50 = 57.3 mu g larva(-1)), whereas cumin was more active on adults of M. persicae (LC50 = 3.2 ml L-1) and M. domestica (LD50 = 31.8 mu g adult(1)). Moreover, when compared at sub-lethal concentrations with the commercial insecticide alpha-cypermethrin, they were definitely devoid of toxic effects on E. fetida and H. cayridis. These results represent a milestone to manufacture and commercialize green formulations to be used in crop protection and to combat insect vectors of public importance.