Biological effects of tea tree (Melaleuca alternifolia L.) oil formulations on Sitophilus granarius L. (col.: curculionidae)

Essential oils (EOs) are vital in pest management for their natural insecticidal properties. Among these EOs, the tea tree oil is considered as an important source of pest management, offering effective control against various pests through its insecticidal properties. Therefore, the current study was designed to examine the efficacy of tea tree oil formulations (F14, F15, F16, F17, and F18) against S. granarius through a series of bioassays including contact toxicity, fumigant toxicity, ovicidal, and larvicidal tests. The contact bioassay results revealed that the F15 (%72.17) and F16 (%79.18) formulations were highly toxic, while F14, F17 and F18 showed moderate toxicity after 120 h incubation. In the fumigant toxicity tests, both F14 (%43.69) and F18 (%22.59) formulations demonstrated significant efficacy, with F14 being slightly more toxic. The ovicidal bioassay results indicated that the F18 formulation had totally reduced the number of emerging adult weevils, showing its strong ovicidal properties. The larvicidal bioassay results further confirmed the effectiveness of the F18 formulation causing total mortality in larval stage. Overall, the results highlighted the potential of tea tree oil formulations, especially F15 and F16 for contact and F18 for fumigant bioinsecticides and can be used as promising alternatives to synthetic insecticides for the management of S. granarius in stored products.