Susceptibility of red flour beetle Tribolium castaneum (Herbst) populations from Serbia to contact insecticides

Contact insecticides remain the principal option for controlling stored-product insects. Unsatisfactory results of insecticide applications are caused by several factors, one of the most important being resistance of stored-product insects. The objective of this study was to examine the susceptibility in several populations of red flour beetle Tribolium castaneum (Herbst) from Serbia to different contact insecticides. Toxicity of the insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and bifenthrin to adults of a laboratory population of T. castaneum was investigated in the laboratory by topical application. At the LD50, deltamethrin was the most toxic and malathion the least toxic of the insecticides. Discriminating dose data for the laboratory population were used to test the susceptibility of 10 other populations originating from different storage facilities (silos, warehouses and flour mills) in Serbia. The discriminating dose of malathion caused mortality of up to 85% in seven populations, indicating malathion resistance in those populations. For two populations of T. castaneum from Nikinci and Jakovo LD values, ld-p lines and levels of susceptibility/resistance (RRs) were determined. The most toxic insecticide for adults from Nikinci and Jakovo was deltamethrin, while malathion was least toxic. The resistance ratios (RRs) for malathion at the LD50 were 17.6 for beetles from Nikinci, and 26.0 for beetles from Jakovo. Keywords: Tribolium castaneum adults; Different populations; Insecticide toxicity; Susceptibility resistanc