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

Authors: ATHANASSIOU, CHRISTOS - University Of Thessaly; Arthur, Franklin; Campbell, James - Jim; DONALDSON, JOHN - Mri Global

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2019
Publication Date: 8/15/2019
Citation: Athanassiou, C.G., Arthur, F.H., Campbell, J.F., Donaldson, J.E. 2019. Particle size matters: Efficacy of aerosols for the control of stored product psocids. Journal of Stored Products Research. 83:148-152. https://doi.org/10.1016/j.jspr.2019.05.006.
DOI: https://doi.org/10.1016/j.jspr.2019.05.006

Interpretive Summary: Psocids are soft-bodied insects that are becoming more of a problem in stored products, leading to contamination issues and rejections of finished products. Recent studies show they are more tolerant to residual contact insecticides compared to stored product beetles, but there is less information on their susceptibility to aerosols. We conducted studies on four psocid species, using a combination product of pyrethrin combined with the insect growth regulator methoprene. We applied the aerosol for 5 to 30 minutes at two particle sizes, 2 and 16 microns, using psocid nymphs as the test life stage, and examined mortality after 5 days. Longer spray times were required to give 100% control at the 2 micron particle size compared to the 16-micron particle size, and mortality varied with species. Results mimic tests done with stored product beetles that showed the larger particles were more effective, but in this test both particle sizes of aerosol gave control of psocids, depending on the spray time, which contrasts with previous results for stored product beetles. However, the larger particle sizes would provide optimum control due to the decreased time required for complete mortality.

Technical 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 aerosol particle sizes against stored-product psocids and could be used as a guide for improved management of psocids.