The efficacy of some synthetic monoterpenes and Yucca extract for controlling Tribolium castaneum (Herbst) in wheat grain

The study's objective was to assess the efficacy and to identify the toxic mechanisms of action of some plant-derived monoterpenes and yucca extract as alternatives to chemical insecticides against the red flour beetle, Tribolium castaneum. Carvone, 1,8-cineole, cuminaldehyde, and linalool, as well as Yucca schidgera extract, were the control agents whose efficacy against the red flour beetle was tested in the laboratory and compared to malathion. The criteria for evaluating efficacy were the effects of the tested compounds on adult mortality and red flour beetle progeny. Furthermore, the effects of the control agents on some enzymes (Acetylcholinesterase, alpha-amylase, and alkaline phosphatase) in T. castaneum were investigated. Moreover, the effect of the tested control measures on weight loss of treated wheat grain was studied. The tested substances showed a high ability to control T. castaneum with regard to adult mortality and offspring production, especially when used as fumigants. For adult mortality, malathion showed the highest potential against T. castaneum as a fumigant, followed by carvone, yucca extract, cuminaldehyde, linalool, and 1,8-cineole with LC50 values of 0.05, 331.5, 365.1, 372.2, 460, and 467.5 mg.1000 cm(-2) after 72 hours, respectively. The highest reduction in progeny was for malathion followed by carvone, linalool, cineole, yucca extract, and cuminaldehyde with reduction percentages of 100, 90, 89.3,79.4 and 65.8%, respectively. The tested compounds significantly affected acetylcholinesterase activity, alpha-amylase activity, and alkaline phosphatase in the red flour beetle. There was no significant reduction in the weight of wheat grains treated with the tested materials compared to the untreated healthy grains. Finally, the tested compounds as fumigants, especially 1,8-cineole, can be considered as effective alternatives to control the red flour beetle.