Effects of aerosol insecticide application location on patterns of residual efficacy against Tribolium confusum (Coleoptera: Tenebrionidae) larvae

Authors: Scheff, Deanna; Campbell, James - Jim; Arthur, Franklin; ZHU, KUN YAN - Kansas State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2020
Publication Date: 6/3/2020
Citation: Scheff, D.S., Campbell, J.F., Arthur, F.H., Zhu, K. 2020. Effects of aerosol insecticide application location on patterns of residual efficacy against Tribolium confusum (Coleoptera: Tenebrionidae) larvae. Journal of Economic Entomology. 113(4):2007-2015. https://doi.org/10.1093/jee/toaa103.
DOI: https://doi.org/10.1093/jee/toaa103

Interpretive Summary: Aerosol insecticides are a valuable tool for food processing facilities since they can apply the insecticide more uniformly within a space then other application methods. However, the method by which an aerosol insecticide is applied can impact spatial pattern of distribution leading to areas with low efficacy. In this study, we investigated the effect application position within a flour mill had on the spatial pattern in insect growth regulator efficacy. The two aerosol insecticide formulations evaluated had very different patterns of efficacy, with one providing relatively uniform high suppression of larval development to the adult stage and the other insecticide having areas with high adult emergence. Application location significantly impacted the spatial pattern of efficacy for one of the aerosol insecticides, with splitting an application among multiple locations providing the most even coverage and prevented >90% of larvae from becoming adults compared to releases from one of three single locations. Regardless of the treatment location or formulation used there were still areas of a mill where little efficacy was observed, so further improvement in application methods is needed.

Technical Abstract: Aerosol insecticides are one tool that pest management professionals can utilize as a spatial treatment inside food facilities such as mills, processing plants, and storage warehouses. However, methods of aerosol application can vary significantly which can impact the spatial pattern of efficacy. We investigated how the location from which an aerosol insecticide is applied influenced the spatial dispersal of the insecticide by evaluating residual activity on concrete surfaces. Concrete arenas were placed out during applications and Tribolium confusum Jacquelin du Val, confused flour beetle, larvae were exposed on treated concrete surfaces at two-, four-, and six-weeks post aerosol application and monitored for adult emergence. Treatments were performed using two commercial aerosol formulations, pyrethrin + pyriproxyfen and pyrethrin + methoprene, applied in one of three static locations or a fourth application comprising of splitting the application among all three locations. The pyriproxyfen formulation had <10% emergence of adults in only three arenas after six weeks and an average efficacy range of 9-18 across all treatments and residual times (efficacy index values range from 1 (low) to 21 (high)). The methoprene formulation had adult emergence after two weeks and efficacy values ranging from 1 to 16 across all treatments by six-weeks post aerosol application. Efficacy index values were high in locations directly in front of the aerosol application and in unobstructed locations. The pyriproxyfen application was more consistent in spatial coverage and residual control compared with methoprene. This study illustrates that the aerosol delivery method and aerosol formulation significantly influenced residual efficacies.