Formulation of Neem Leaf and Croton Seed Essential Oils as a Natural Insecticide Tested on Mosquitoes and Cockroaches

[Image: see text] Essential oils are highly aromatic plant oils utilized as a new insect control alternative to synthetic insecticides because of environmental concerns. As a result, the purpose of this study was to evaluate the effects of essential oil extraction conditions on neem leaf and cotton seed, as well as to identify their chemical composition using gas chromatography–mass spectrometry. Moreover, both extracted oils were subjected to bioinsecticide formulation in individual as well as mixed forms, which were tested on mosquitoes and cockroaches using the conventional roach killer and a blank control as a comparison. The results revealed that the maximum yields of essential oils from neem leaf and croton seed were respectively 30.54 and 14.75%. The extraction process was greatly affected by the particle sizes because of the mass transfer limitation between solute–solvent interactions. The insecticidal evaluation showed that the blended form of essential oils at the 20% concentration has better efficiency than the individual oils, which accounted for 80% mosquito and 71.8% cockroach death rates within 4 h, whereas the synthetic roach killer completely killed all of the insects within the same time frame. Terpineol, α-terpinyl acetate, eucalyptol, and δ-cadinene are the active insecticidal compounds in neem leaf oil, whereas the active compounds of croton seed oil are epiglobulol, copaene, δ-cadinene, α-cubebene, and β-guaiene.