Pesticide Resistance in Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae) from Flour Mills in the United States

Field strains of confused flour beetle, Tribolium confusum Jacquelin du Val, and red flour beetle, Tribolium castaneum (Herbst), were collected from flour mills throughout the United States and tested with discriminating doses to determine their resistance to pesticides. Of 17 strains of T. confusum, 82% were resistant to malathion, 53% were resistant to chlorpyrifos-methyl, 24% were resistant to dichlorvos, 18% were resistant to phosphine, and none was resistant to synergized pyrethrins or resmethrin. Of 28 strains of T. castaneum, 93% were resistant to malathion, 64% were resistant to dichlorvos, 46% were resistant to phosphine, 36% were resistant to chlorpyrifos-methyl, and none was resistant to synergized pyrethrins or resmethrin. Generally, T. castaneum was more resistant than T. confusum. The frequency of this gene for malathion resistance in T. castaneum was sufficiently high to contribute to control failures in the field.