Particle size matters: Efficacy of aerosols for the control of stored product psocids

Abstract

The insecticidal effect of an aerosol formulation that contained a 100: 1 mixture of pyrethrin and methoprene (by volume), was evaluated for control of nymphs of four stored-product psocid species, Liposcelis bostrychophila, L. decolor, L. entomophila and L. paeta. The aerosol was applied at two particle sizes, 2 and 16 μm. The application time of the aerosols was 0 (untreated controls, no aerosol), 5, 10, 20 and 30 min. Nymphs were examined at 5 days post-treatment. The aerosol was effective on all species tested, with mortality of 100% after 5–20 min, depending on the species. There was a strong interaction between the application time and the particle size. In all cases, the application of the aerosol at 16 μm was more effective than 2 μm for all species. Moreover, the application at 16 μm required less time to reach 100% mortality, suggesting that this particle size may provide a more cost-effective application, as it requires less formulation and a considerably shorter application time. Our results provide the first series of data for the application of aerosols at different particle sizes against stored-product psocids and could be used as a guide for improved management of psocids. © 2019 Elsevier Ltd