Sanitation increases effectiveness of aerosol insecticides in milling facilities

Earlier studies have shown that accumulated dust and food residues in flour mills can potentially decrease the efficacy of contact insecticides used against adult and immature stages of stored product insects. A study was conducted to evaluate effects of flour residues on the efficacy of synergized pyrethrin aerosol against different life stages of the confused flour beetle, Tribolium confusum (Tenebrionidae). Twenty individuals of the adult, pupal, and larval stages were exposed to aerosol spray separately in Petri dishes containing 0, 0.1, 1, 5 or 10 g of wheat flour held inside empty sheds. After 2 h of exposure, the dishes were taken out of the sheds and placed in an incubator set at 27°C-60% RH. Adult mortality was assessed at 2, 5, 8, and 15 days post-exposure, while pupae and larval mortality were assessed at 21 and 28 days post-exposure respectively. Additionally, adult recovery after exposure was recorded for each of the flour depths. Mortality of adult beetles decreased with increasing depth of flour. Also, recovery of moribund insects increased with depths of 5 and 10 g flour compared to dishes with 0, 0.1, or 1 g of flour. Similarly, larvae and pupae were less affected when exposed in deeper flour dishes. Results suggest accumulated flour residues during application of an aerosol can reduce effectiveness, therefore sanitation should be emphasized prior to aerosol application.