Spatial pattern in aerosol insecticide deposition inside a flour mill
2014
Campbell, James F. | Arthur, Frank H. | Zhu, Kun Yan
Aerosol insecticides are commonly used for management of stored-product pests inside food facilities, but the physical complexity of the interior of most food facilities may influence the dispersal and deposition of aerosol droplets and create spatial variation in efficacy. The spatial pattern in aerosol insecticide deposition was evaluated inside on multiple floors of a flour mill using a high density grid of bioassay dishes containing adult Tribolium confusum Jacquelin du Val. Three aerosols, Aerotech with NyGuard, Pyrocide 100 + Diacon II, and Vap20, were evaluated at normal (27 °C) and high (40 °C) target temperatures. For the two pyrethrins insecticides, Aerotech and Pyrocide, there was spatial variation to efficacy assessed using a newly developed efficacy index, which was relatively consistent among floors, but varied with aerosol formulation and temperature. Walls and corners, especially behind the direction of application, and the far corner of the room had zones of lower efficacy, while open areas in the center of the room had the highest efficacy. The organophosphate insecticide, Vap20, provided high efficacy at all locations, probably due in part to its vapor toxicity. Using boxes 1 m deep and 5, 10 or 20 cm high and open on only one end, the relationship between gap height and aerosol dispersal under horizontal surfaces was also determined using the efficacy index. These results show the potential for spatial variation in aerosol efficacy within a food facility and identify locations that are likely to receive lower dosages of insecticide and need supplemental treatment to maximize overall efficacy.
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