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Susceptibility of different life stages of Tribolium confusum to pyrethrin aerosol: effects of a flour food source on insecticidal efficacy

Kabita Kharel, Frank H. Arthur, Kun Yan Zhu, James F. Campbell, Bhadriraju Subramanyam
Journal of pest science 2014 v.87 pp. 295-300
Tribolium confusum, aerosols, cleaning, direct contact, grain dust, imagos, insect control, insecticidal properties, insecticides, larvae, mortality, pupae, pyrethrins, sanitation, storage insects, wheat flour
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.