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Title: Residual efficacy of pyrethrin+methoprene for control of Tribolium castaneum and Tribolium confusum in a commercial flour mill

item Arthur, Franklin

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2015
Publication Date: 8/15/2015
Publication URL:
Citation: Arthur, F.H. 2015. Residual efficacy of pyrethrin+methoprene for control of Tribolium castaneum and Tribolium confusum in a commercial flour mill. Journal of Stored Products Research. 64(PartB):42-44. doi: 10.1016/j.jspr.2015.08.001.

Interpretive Summary: Aerosol insecticides are used to control insects in flour mills, but there are concerns about how well these aerosols are distributed in practical situations. Concrete treatment arenas were exposed with and without flour inside a flour mill that regularly used an aerosol application of pyrethrin combined with Diacon® II, an insect growth regulator that prevents normal development of insect larvae. Results show the insecticide was effective for up to 7 weeks, but there was less control of red flour beetles and confused flour beetles in arenas that were placed in areas where there was limited dispersal of the aerosol. Also, the confused flour beetle was harder to control with the insecticide compared to the red flour beetle. Management personnel can use the results to identify areas within flour mills where aerosol dispersion might be limited, and also to plan appropriate control programs for specific flour beetle species.

Technical Abstract: Concrete arenas with and without flour were placed in open, obstructed, and hidden positions inside a commercial flour mill and exposed to a combination treatment of pyrethrin + methoprene. Bioassays were conducted 1, 3, 5, and 7 weeks after the arenas were treated by adding flour to those arenas that were exposed without flour, and then placing late-stage larvae of either Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum Jacqueline DuVal, the confused flour beetle, on an individual arena. There were no differences in adult emergence of either species on any of the exposed arenas in any position for the residual bioassays, indicating no loss of effectiveness of the insecticide. There was less adult emergence of both species on arenas that had contained flour when they were exposed to the aerosol compared to those exposed without flour and then flour added for the bioassay process. Adult emergence of both species was also lower in arenas with flour in the open position compared to those in the hidden and obstructed positions but regardless of exposure position or whether or not the arenas contained flour when they were exposed to the aerosol, adult emergence was greater in T. confusum than in T. castaneum. Results show how species variability and the presence of structural barriers within a facility can affect susceptibility to aerosol insecticides.