Laboratory and field studies were conducted to determine if accumulation of a flour food source or milling debris affected residual efficacy of beta-cyfluthrin for control of Tribolium castaneum (Herbst), the red flour beetle. In the laboratory study, the high label rate of 20 mg active ingredient (AI)/m² gave effective control for 8 wks, regardless of whether or not the concrete was sealed prior to application or the presence of flour contamination. However, with the low label rate of 10 mg AI/m², the flour apparently absorbed the insecticide residues from the treated surface, and sealing the concrete did not have a beneficial effect on efficacy. Two field studies with the low label rate were conducted during autumn of 2012 and 2013 and summer of 2013, using only unsealed concrete. Accumulated milling debris caused a reduction in efficacy in the autumn studies, as shown by increased time to 100% knockdown, decreased mortality, and decreased residual efficacy. There was no such corresponding decrease in residual efficacy in the summer study. Overall, results of both studies show that accumulated food and milling debris can absorb residue of beta-cyfluthrin from a treated surface and have a negative impact on residual efficacy, particularly with the low label rate of 10 mg AI/m².