Chemical composition, fumigant toxicity and biochemical and anti-nutritional effects of the essential oil of Eucalyptus oleosa Muell. against the lesser grain borer, Rhyzopertha dominica (F.)

The lesser grain borer, R. dominica, causes extensive quantitative and qualitative loses on stored cereal grains. The use of synthetic chemicals in the management of such insect pests resulted in several side effects such as environmental contamination, potential impacts on human health and development of pest resistance. Promising insecticidal potential of the essential oils isolated from several species of Eucalyptus genous against insect pests was shown in recent study. In this study, the lethal and sublethal effects of E. oleosa essential oil were investigaetd against the adults of R. dominica.  Chemical analysis of the essential oil indicated that terpenes, including 1,8-cineole, α-pinene, trans-pinocarveol, (s)-α-terpineol, and β-eudesmol, had high amount. The adult insects were susceptible to the fumigation of essential oil so that LC50 (Lethal Concentration to kill 50% of insects) values were estimated as ‎42.923, ‎35.828, and ‎34.044 µl/l air after 24, 48 and 72 h, respectively. Despite increases in a- and β-estearse enzymes, total protein, glycogen, and lipid contents and digestive amylolytic and proteolytic activities of the adults treated with LC30 (Lethal Concentration to kill 30% of insects) of essential oil were significantly decreased in comparision with the control. The consumption index (CI), relative consumption rate (RCR), and relative growth rate (RGR) were also significantly decreased in treated adults. A 59.40% feeding deterrence index (FDI) was evaluated for insects treated with LC30 of  the essential oil. According to observed lethal and sublethal effects, the essential oil of E. oleosa can be considered in further investigations in the management of R. dominica.