Toxicity of Some Insecticides to the Red Flour Beetle, Tribolium castaneum

A laboratory experiment was conducted in 1960 comparing the toxicity of parathion, Diazinon® (O,O-diethyl O-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate), endrin, malathion, dieldrin and DDT to Tribolium castaneum (Herbst) (Tenebrionidae—Coleoptera), a storage pest. The insecticides were formulated in the laboratory from the technical grades and used in the form of emulsion. Benzene and Triton X-100 were used as solvent and emulsifier, respectively, and their proportion in the final formulation being kept as 5% w/v of the solvent and 0.625% w/v of the emulsifier. Approximately 5,000 adult beetles reared in the laboratory were kept in petri dishes and were sprayed directly under Potter's tower. Observations on mortality were recorded 72 hours after spraying. When the values of L.C.50 were taken into consideration the order of toxicity of different insecticides were: parathion>Diazinon >endrin>malathion>dieldrin>DDT. Thus parathion, Diazinon, endrin, malathion and dieldrin were found to be more toxic than DDT, i.e., 84.1, 62.4, 17.3, 14.8 and 2.3 times, respectively, as toxic as DDT.