Insecticide activity of essential oil of Litsea cubeba (Lour.) Pers. and its major component citral against Drosophila suzukii: Histological and ultrastructural assessment

Application of synthetic insecticides is the most frequently used method for controlling pests. However, their indiscriminatory use has led to the development of resistance and high insecticide residues in the environment. Natural products that have low mammalian toxicity with low environmental impact, are viable alternatives to synthetic pesticides. This study aimed to evaluate the contact, fumigant toxicity, and repellent activity of Litsea cubeba essential oil (EO) and its major compound citral against Drosophila suzukii (Matsumura). The morphological alterations in target organs and microscopic damage were observed by scanning electron microscopy (SEM) and light microscopy. Contact exposure to Litsea cubeba EO at 1.0 μL/cm² resulted in mortality of 91.67% in 24 h. Fumigant toxicity assay showed that larvae mortality reached 100% when Drosophila adults were exposed to 100 μL/L Litsea cubeba EO within 24 h. Litsea cubeba EO was most repellent at 1.0 μL/cm². The symptoms caused by Litsea cubeba EO and citral on larval epidermis was uneven pigmentation and darkening of body. In the SEM images, treated Drosophila larvae exhibited a dry cuticle surface, sensory distortions, and general degeneration. The intensified cytoplasmic vacuolation and necrosis of the intestinal tract were observed in the photomicrographs with both extracts. This study showed that Litsea cubeba EO can be utilized as a bioinsecticide against Drosophila, making it an environmentally safer option for pest management in fruit and vegetable preservation.