Evaluation of citronella oil nanoemulsion formulation against the insect-stored pest Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae)

Citronella (Cymbopogon nardus) produces essential oil and has the potential to be developed as a botanical insecticide. However, in its development, botanical insecticides encountered several obstacles. Utilizing nanotechnology in nanoemulsion preparations is one method to overcome these challenges. This research aimed to determine the contents of the citronella oil nanoemulsion (CiONano) and citronella oil non-nano emulsion (CiONonNano) formulations and evaluate the toxicity, repellency, and prevention of oviposition against female adults of Callosobruchus maculatus. This was the first work to evaluate the nanoemulsion of citronella oil prepared from spontaneous emulsification against C. maculatus. Chemical content testing used the GCMS method. A toxicity test using the contact method (LC50), used a probit program, while testing for repellency and oviposition deterrence was carried out using the no-choice method. The highest chemical component of CiONonNano and CiONano was citronella (37.56 and 38.97%, respectively), followed by citronellol (17.71 and 18.99%, consecutively) and geraniol (14.78 and 15.38%, respectively). In general, the CiONano formulation showed higher repellency and toxicity than CiONonNano. The LC50 values of CiONano were 10.03%. These values were 4.49 times lower than the LC50 of CiONonNano. However, the results of the oviposition inhibition test showed different results, the CiONonNano formulation had a higher oviposition inhibition capacity for adult female C. maculatus than CiONano. As a result, it is necessary to optimize the CiONano formulation to obtain consistent results in controlling C. maculatus.