Mixing essential oil-based nanoemulsions: A step towards the generation of effective green grain protectants

Abstract: The insecticidal activity of essential oils (EOs) can be enhanced by their
encapsulation into nanoemulsions (NEs). In the current study, we evaluated the adulticidal
efficacy of two EO-based NEs containing different combinations of Pimpinella anisum,
Trachyspermum ammi, Carum carvi and Cuminum cyminum (Apiales: Apiaceae) against
Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae), Tenebrio molitor
(Coleoptera: Tenebrionidae), Trogoderma granarium (Coleoptera: Dermestidae) and Acarus
siro (Sarcoptiformes: Acaridae). Concerning mortality of T. castaneum, 500 ppm and 1000 ppm of the 3 % (w/w) T. ammi + 3 % (w/w) C. carvi EO-based NE killed 61.1 and 84.4 % of the exposed adults, respectively, 7 days post-exposure. Mortality rates of T. confusum ranged
between 6.7 and 15.6 % for all tested EO-based NEs and their concentrations after 7 days of
initial exposure. Both the EO-based NEs caused moderate mortality to T. molitor that did not
exceed 70.9 % for 1000 ppm of the 3 % (w/w) T. ammi + 3 % (w/w) C. carvi EO-based NE and 67.6 % for 1000 ppm of the 2 % (w/w) P. anisum + 2 % (w/w) C. cyminum + 2 % (w/w) T. ammi EO-based NE at the end of the experimental period. Trogoderma granarium was the most susceptible species reaching 100.0 % and 96.4 % mortality after 7 days of exposure to 1000 ppm of the 2 % (w/w) P. anisum + 2 % (w/w) C. cyminum + 2 % (w/w) T. ammi and the 3 % (w/w) T. ammi + 3 % (w/w) C. carvi EO-based NEs respectively. Regarding A. siro, mortalities were low to moderate ranging from 23.0 to 73.1 %, 7 days post-exposure. Our results indicate that the efficacy of the two tested EO-based NEs is a species-dependent phenomenon.