Location: Stored Product Insect Research Unit
Title: Susceptibility of different life stages of Tribolium confusum to pyrethrin aerosol: effects of flour source on insecticidal efficacy Authors
Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2013
Publication Date: N/A
Interpretive Summary: The presence of food material on surfaces can enable adult flour beetles to survive exposure to contact insecticides. Aerosols are commonly used as space treatments for large-scale applications inside flour mills, but the level of sanitation at time of treatment impacts the amount of food material on surfaces and could affect the performance of these aerosols. We placed different life stages of the confused flour beetle in dishes with flour and then exposed them to pyrethrin aerosol. As more flour was added to a dish more larvae and pupae were able to develop to the adult stage after the initial exposure. When little or no flour was in the dish, all exposed adults of both species were immobilized by the aerosol and did not recover, but as more flour was added to the dish less adults were immobilized and more eventually recovered. Results show the effectiveness of aerosol insecticides is clearly reduced when food material is present, and insect management programs for flour mills should emphasize cleaning and removal of food residues prior to aerosol application.
Technical Abstract: Accumulated grain dust and flour residues in flour mills can potentially decrease the efficacy of contact insecticides used for control of adult and immature stages of stored product insects. A study was conducted to evaluate the effects of flour residues on the efficacy of synergized pyrethrin aerosol against different life stages of the confused flour beetle, Tribolium confusum Jacquelin du Val. Twenty individual adults, pupae, or larvae of T. confusum, confined in Petri dishes containing 0, 0.1, 1, 5 or 10 g wheat flour, were exposed separately inside an empty shed to the aerosol spray. After 2 h of exposure, all dishes were removed from the shed and placed in an incubator set at 27°C and 60% RH. Mortality of T. confusum adults decreased with increasing depth of flour. Recovery of moribund adults at 15-d exposure was greater in the 5 and 10 g flour dishes (15 and 46% respectively) compared to the 0, 0.1, or 1 g flour dishes (0, 0.7, and 5% respectively). Similarly, larvae and pupae were less affected at greater flour depths. Results show accumulated flour residues during aerosol application can compromise its effectiveness against insects. Reduced efficacy at greater flour depths also suggests lower penetration ability of pyrethrin aerosols. These results emphasize the importance of sanitation and cleaning to remove spillage and extraneous material prior to an aerosol application.