Botanical innovation in grain storage: Dual insecticidal and acaricidal activity of Commiphora myrrha essential oil in stored wheat

The search for effective botanical alternatives to synthetic insecticides in stored-grain protection is intensifying due to resistance development and regulatory restrictions of the latter. The current study evaluated the acaricidal and insecticidal effectiveness of Commiphora myrrha essential oil (EO), rich in furanosesquiterpenes, against three stored-product pests of wheat: Acarus siro adults and nymphs, Trogoderma granarium larvae and adults, and Rhyzopertha dominica adults. The myrrh EO main constituents were furanoeudesma-1,3-diene, curzerene, lin- destrene, and isofuranodiene. Hard wheat was treated with two concentrations of C. myrrha EO (500 and 1000 ppm) and compared with pirimiphos-methyl at the label concentration (5 ppm). Mortality was assessed from 4 h to 7 days of exposure. The EO demonstrated species- and stage-dependent efficacy, while outperforming the synthetic insecticidal agent in many cases. Trogoderma granarium adults were the more susceptible devel- opmental stage (100 % mortality at 6 d at 1000 ppm), followed by A. siro adults (77.8 % mortality at 7 d at 1000 ppm). In contrast, R. dominica adults (71.1 % mortality at 7 d at 1000 ppm) and A. siro nymphs (68.9 % mortality at 7 d at 1000 ppm) showed moderate mortalities and T. granarium larvae (25.6 % mortality at 7 d at 1000 ppm) high tolerance. The pronounced adulticidal activity against T. granarium and the documented acar- icidal effect against A. siro indicate that C. myrrha EO may serve as a multi-targeting grain protectant. This dual action enhances the potential integration of C. myrrha EO into sustainable stored-product pest management programs.