Insecticidal synergy of essential oils from Cymbopogon citratus (Stapf.), Myristica fragrans (Houtt.), and Illicium verum Hook. f. and their major active constituents.

[Display omitted] • Some plant essential oils are effective against Musca domestica. • C. citratus , M. fragrans , and I. verum oils are even synergistic against it. • 0.5 % I. verum oil + 0.5 % geranial active constituent was the most synergistic. • 0.5 % I. verum oil + 0.5 % geranial shows the highest insecticidal activity. • This formulation has the highest potential for green insecticidal application. This study attempted to find safe and effective green insecticidal agents against Musca domestica L., which is a major public health pest in tropical and subtropical countries that have already developed resistance to synthetic pesticides. Plant essential oil-based insecticides are new, effective, and eco-friendly alternatives. Today, they are a housefly control method of choice. The study evaluated the insecticidal effect against M. domestica adults of essential oils (EOs) from Cymbopogon citratus (Stapf.), Illicium verum Hook. f., and Myristica fragrans (Houtt.) as well as their major active chemical constituents. Formulations of these individual and combined compounds were evaluated to see whether they were synergistic against M. domestica. Chemical compositions of these EOs were also analyzed by GC–MS. The major constituent of C. citratus was found to be geranial (45.4 %); that of I. verum was trans -anethole (94.0 %), and that of M. fragrans was α-pinene (21.6 %). Formulation CB3 (0.5 % I. verum EO + 0.5 % geranial) exhibited the highest synergistic effect (SI = 0.04), with 100 % knockdown and mortality rates, a 50 % knockdown time (KT 50) of 4.0 min, and a 50 % lethal time (LT 50) of 6.0 min. CB3 was more effective than 1% w/v cypermethrin, followed by CB5 (0.5 % M. fragrans EO + 0.5 % geranial), CB7 (0.5 % α-pinene + 0.5 % geranial), and CB8 (0.5 % geranial + 0.5 % trans -anethole). To conclude, some formulations of combined C. citratus , I. verum , and M. fragrans were strongly synergistic against M. domestica and more effective than cypermethrin. Moreover, since they have been long used as natural food ingredients and in traditional medicine, they are also safe for humans, non-target organisms, and the environment. [ABSTRACT FROM AUTHOR]