Dispersion, efficacy, and persistence of dichlorvos aerosol against two flour beetle life stages in a mill

•Concrete arenas were placed in open, obstructed, and concealed locations among five floors of a flour mill.•Each mill floor was subjected to dichlorvos aerosol application at the labeled rate.•Tribolium confusum adults and Tribolium castaneum pupae were exposed in different locations to the aerosol.•Direct dichlorvos exposure resulted in 99-100% knockdown and/or mortality of Tribolium spp.•Dichlorvos residues on concrete arenas aged for an additional 24 h had little or no activity against both species.

The dispersion, efficacy, and persistence of dichlorvos applied as an aerosol inside the Kansas State University pilot flour mill was evaluated based on responses of adults of the confused flour beetle, Tribolium confusum, and pupae of the red flour beetle, Tribolium castaneum, during and after application. Dichlorvos was applied at the highest labeled rate of 0.35 g/m3. Concrete arenas with or without different life stages of the two species were placed in open, obstructed, and concealed mill locations during aerosol application. Knockdown and mortality of T. confusum adults was 99-100% and mortality of T. castaneum pupae was 97-100% in open and obstructed mill locations, indicating uniform dispersion of dichlorvos. In concealed locations, knockdown and mortality of T. confusum adults and mortality of T. castaneum pupae was 85-94%, indicating effective dispersion of dichlorvos into pieces of equipment. Holding insects directly exposed to dichlorvos for an additional 24 h in the same arenas did not increase knockdown or mortality. Exposure to dichlorvos residues aged for an additional 24 h on concrete resulted in moderate to poor knockdown and/or mortality of Tribolium spp. suggesting lack of residual activity. Results show dichlorvos will give immediate kill of exposed insects but will not offer effective residual control.