Modeling and optimization of the toxicity of Eucalyptus Procera Dehnh essential oil against Tribolium castaneum Herbst

The use of synthetic pesticides is the main strategy for managing stored-product insect pests such as the red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). However, their abuse resulted in several side effects, including environmental pollution, human health risk, effects on non-target organisms, and the development of pest resistance. The promising insecticidal effects of plant-derived essential oils, as eco-friendly substitutions to synthetic chemical, has been documented in recent studies. The insecticidal effects of several species from Eucalyptus genus have also been reported in the previous studies. In the present study, the fumigant toxicity of essential oil extracted from the leaves of Eucalyptus procera was evaluated at five concentrations and three exposure times (۲۴, ۴۸, and ۷۲ h) against ۱ to ۷ day-old adults of T. castaneum. The modeling and optimization of mortality data were done by RSM (Response Surface Methodology). The mathematical model between independent (essential oil concentration and time) and dependent (insect mortality) variables measured by multiple linear regression analysis in the following form: Y=βo+∑_(i=۱)^k▒〖β_i X_i+〗 ∑_(i=۱)^k▒〖β_j X_j+〗 ∑_(i=۱)^k▒ ∑_(j=۱)^k▒〖β_ij X_i X_j 〗+∑_(i=۱)^k▒〖β_jj X_j^۲ 〗, in which Y is the dependent variable, Xi and Xj are independent variables, k is the quantity of independent variables, βo is the intercept of the model, βi and βj are the coefficients of the linear parameters, and βij is the coefficient of a quadratic parameter. E. procera essential oil exhibited potential concentration-time dependent fumigant toxicity against T. castaneum. Correlation coefficients of determination (R۲), adjusted R۲, and predicted R۲ were ۰.۹۶, ۰.۹۵, and ۰.۹۴, respectively, indicating the positive effects of essential oil concentration and time on insect pest mortality. A quadratic polynomial equation was realized for the mortality of insect pest using multiple regression analysis: Mortality = +۴.۸۰ – ۰.۳۹(A) + ۳.۵۸(B) + ۰.۰۲(AB) + ۶.۵۱(A۲) – ۰.۰۴(B۲), in which A and B are the exposure time and essential oil concentration, respectively. Optimization results revealed that ۲۴.۸۹ µL/L of essential oil and ۶۶.۰۲ h-exposure time would be sufficient for ۱۰۰% mortality of insect pest. According to the results of present study, the Response Surface Methodology can be used as a suitable method for modeling and optimization of insecticidal activity of E. procera essential oil. Furthermore, the essential oil of E. procera with promising insecticidal activity against T. castaneum can be considered as an effective and sustainable alternative to detrimental synthetic chemicals.

کلیدواژه ها:

Essential oil ، Eucalyptus procera ، Fumigant toxicity ، Optimization ، Stored-product insect pest.