Abstract
Mites are one of the most notorious and destructive pests affecting stored grains, contaminating stored grain with toxins and reducing germination rates. Applying synthetic miticides is the sole method for providing knockdown control of mites; however, the continuous application of miticides results in the contamination of grain with highly persistent toxic residues, which pose a health hazard to humans. The present research evaluates the efficacy of crude aqueous extracts of Azadirachta indica, Melia azedarach, Eucalyptus sp., Datura stramonium, and Citrullus colocynthis under laboratory conditions at 5 concentrations (6.25%, 12.5%, 25%, 50%, and 100%) and 4 exposure periods (7, 14, 21, and 28 days) against Rhizoglyphus tritici (Acari: Acaridae) with the aim of exploring safe, natural grain protectants as alternatives to toxic synthetic miticides. There were concentration-and exposure-period-dependent EC50 and ET50 levels and efficacy against mites among all extracts, and levels increased significantly with increasing concentrations and exposure periods for all extracts. Regression equations and their probability values against EC50 and ET50 for each plant extract revealed a significant and positive role in mite population inhibition. Azadirachta indica, D. stramonium, M. azedarach, and C. colocynthis extracts were highly and equally effective, and their EC50 ranged between 5.23% and 8.13% at 28 days of exposure (approximately 3.5-5.4 times less than levels in Eucalyptus sp. leaf extract); ET50 was in the ranges of 0.56-1.20, 1.90-2.70, 8.20-14.50, 15.47-24.67, and 24.75-39.58 days (approximately 12, 8-11, 3-4, 7-11, and 11-17 times less than Eucalyptus sp. leaf extract) at 100%, 50%, 25%, 12.5%, and 6.25%, concentrations, respectively. This study highlights an opportunity to develop natural molecules from A. indica, C. colocynthis, M. azedarach, and D. stramonium extracts as acaricides.