The red flour beetle (Tribolium castaneum Herbst), a major pest of stored grains in tropical and subtropical regions, causes significant economic losses in several agricultural storage items. This research investigates the use of aqueous plant extracts and synthetic insecticide (deltamethrin) for the sustainable and safe management of the red flour beetle. Aqueous extracts from five plant species – Alpinia galanga, Azadirachta indica, Curcuma longa, Nicotiana tabacum, and Nicotiana rustica – were evaluated at six different concentrations (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0%) along with deltamethrin against T. castaneum. Toxicity (both contact and residual) was assessed after 24, 48, 72, and 96 hours using a completely randomized design with four replications. Probit analysis was carried out to determine LC50 and LC90 values. Results revealed that, generally, the mortality of T. castaneum increased as the concentration and exposure time increased. Deltamethrin exhibited the highest contact toxicity overall, with an LC50 of 0.88 ppm and LC90 of 4.74 ppm, and the highest residual toxicity showed the lowest LC50 (0.93 ppm) and LC90 (3.83 mol/L) after a 96 h exposure period. Among the plant species extracts in contact toxicity, N. rustica showed the highest toxicity with an LC50 of 1.00 g/L and LC90 of 5.38 g/L, followed by N. tabacum (LC50 of 1.09 g/L and LC90 of 6.50 g/L). In residual toxicity tests, among the plant species, N. rustica again had the highest toxicity in residual tests with an LC50 of 0.79 g/L and LC90 of 10.37 g/L, followed by N. tabacum (LC50 of 1.18 g/L and LC90 of 9.02 g/L) and A. indica (LC50 of 1.82 g/L and LC90 of 22.36 g/L). The findings suggest that deltamethrin is recommended for managing T. castaneum; however, N. rustica, N. tabacum, and A. indica can effectively control T. castaneum and may be useful in developing novel biopesticides.