Survival of red flour beetles after exposure to cyfluthrin: Effects of a food source
Dr. Frank Arthur

Introduction:Food warehouses, processing plants, and mills often contain residual food and hidden areas that support insect infestations. Sanitation programs for these indoor storage structures include the use of residual insecticides as crack and crevice treatments or spot treatments. However, insects may encounter the insecticidal residues for comparatively brief intervals during normal foraging and feeding activity. The objectives of this test were to determine: 1) the exposure intervals required to kill red flour beetles exposed on concrete treated with cyfluthrin wettable powder (WP), and 2) effects of a food source on beetle survival.

Methods:Adult red flour beetles were exposed for 15, 30, 45, 60, 75, 90, or 120 minutes on concrete treated with cyfluthrin WP, then removed and classified as either knocked down or running, and held for 1 week at approximately 72 °F in new Petri dishes that were either empty or contained 1 gram of flour. Beetles that were upright and running after 1 week were considered to have survived exposure to cyfluthrin. Tests were repeated on the same treated dishes with new beetles every 2 weeks for 16 weeks.

Results:The percentage of beetles that were knocked down after they were exposed on the concrete increased as exposure interval increased and decreased as residues aged.

Until week 8, survival was < 5% when beetles were exposed for > 30 minutes and not given food. After week 8, survival increased at exposure intervals >30 minutes, and by week 16, survival usually exceeded 50%

 In contrast, survival of beetles provided with flour exceeded 80% by week 8.

Conclusions:These results demonstrate that residual food and trash material within storage structures may have a negative impact on the efficacy of residual insecticides such as cyfluthrin. The flour could have either provided nutrition to enhance survival or given the beetles a means to physically remove insecticide particles from the exterior cuticle. Increased emphasis should be given to cleaning and removing residual trash material before insecticides are applied.