Toxic Effects of Nanoemulsions Prepared from Melia azedarach and Peganum harmala Extracts on Eggs and Adults of the Southern Cowpea Beetle, Callosobruchus maculatus

Melia azedarach and Peganum harmala oils extracted with ethanol and emulsified with a hybrid emulsifying agent provided the required nanoemulsion of the oils. The nano-products were characterized using several techniques like transmission electron microscopy to determine the diameter of the nanoemulsion droplets. The droplets of the two emulsions were almost spherical and non-clustered. On average, nanoemulsions' diameter was 36.37 nm for M. azedarach oil and 52.15 nm for P. harmala oil. Two and three-dimensional images obtained by atomic force microscopy (AFM) of the droplets of the nanoemulsion of M. azedarach and P. harmala oils were reasonably homogeneous irregular spheres of the size of 60.54 nm for M. azedarach oil and 86.35 nm for P. harmala oil. The stability of the nanoemulsion during a storage period was 1 month as no separation of layers was observed up to 25.5°C. The nanoemulsion of M. azedarach and P. harmala oils at a concentration of 1500 ppm against Callosobruchus maculatus F. eggs were ovicidal, and 63.43% and 56.83% mortality were recorded, respectively. The highest mortality rate was 97.5% and 54.17% of the adult females after 72 h by nanoemulsions of M. azedarach and P. harmala oil, respectively. It was obvious that these environment-friendly botanicals could be safe alternatives as nanoemulsions for targeted delivery in combating the southern cowpea beetle, C. maculatus, instead of chemical pesticides.. KEYWORDS :Callosobruchus maculatus, Melia azedarach, Nanoemulsions, Ovicides, Peganum harmala, Southern cowpea beetle