Measured efficacy, bioaccumulation, and leaching of a transfluthrin‐based insecticidal paint: a case study with a nuisance, nonbiting aquatic insect

Abstract

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. This study was initiated because a nuisance net-spinning caddisfly, Smicridea fasciatella, is lowering the quality of life for riverfront residents at the type locality. 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 (⊎ ± S.E. = 0.008 ± 0.001, P < 0.001) and a coarse texture maintained greater efficacy (⊎ ± S.E. = −3.7 ± 1.3, 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 h of direct exposure the concentration of transfluthrin was 25.3 ± 0.9 ng/caddisfly with a maximum concentration of 345 ng/caddisfly after 7 days. CONCLUSION: Our predictions were validated with measured, time-dependent impacts on efficacy, leachability, and bioaccumulation. Because of the mobility of active ingredient in the environment, insecticidal paints merit low-impact protocols to improve public health outcomes and environmental safety.

Comparative Efficacy of Pyrethroid-Based Paints against Turkestan Cockroaches

“…Currently, limited information is available regarding the effects of environmental factors on the efficacy of insecticide-based paints. By evaluating the potential washoff of a transfluthrin-based IP through water immersion tests simulating a rain event, the minimum mass loss of transfluthrin has been estimated to range between 0.007 and 0.013% from the original paint concentration [ 41 ]. This loss of transfluthrin is many orders of magnitude lower than those reported for wettable powder and emulsifiable concentrate pyrethroid residual sprays (5.4 and 14.1%, respectively) [ 42 ].…”

“…is a concern with the use of pyrethroid-based paints [43]. Outdoor painted applications are subject to a variety of physical surface conditions and abiotic factors that can decrease insecticide efficacy over time [41]. Therefore, continuous exposure to sublethal doses of insecticides could select resistant individuals [44].…”