LAUSR

BACKGROUND Pest management professionals will require a diverse, adaptive abatement toolbox to combat advanced challenges from disease vector and nuisance insect populations. Designed for post-application longevity, insecticidal paints offer extended residual effects on targeted insect pest populations; a measured understanding of active ingredient bioavailability over time is valuable to fully assess treatment efficacy and potential environmental risks. Here, the study species was a nuisance net-spinning caddisfly, Smicridea fasciatella, which is lowering the quality of life for riverfront residents at the type locality and prompted this study. RESULTS We tested the efficacy and potential mobility of a transfluthrin-based paint (a.i. 0.50%), comparing the impacts of UV exposure and substrate texture over time. Direct UV exposure decreased efficacy (β ± S.E. = 0.008 ± 0.001, p < 0.001) and a coarse texture maintained greater efficacy (β ± S.E. = -3.73 ± 1.32, p = 0.004) over time. Notably, the coarse texture + indirect UV treatment maintained 100% mortality after 240 days. UV exposure and substrate texture did not have a significant impact on leachate concentrations over time, and successive immersion tests indicated a two-phase emission pattern. Bioaccumulation increased with time on the cuticle of dead adult S. fasciatella; after 24 hr of direct exposure was 25.3 ± 0.9 ng/caddisfly with a maximum concentration of 345 ng/caddisfly after seven days. CONCLUSION Our predictions were validated with measured, time-dependent impacts on efficacy, leachability, and bioaccumulation. Considering its mobility in the environment, insecticidal paints merit low-impact protocols to improve public health outcomes and environmental safety. This article is protected by copyright. All rights reserved.