Impact of sublethal exposure to a pyrethroid-neonicotinoid insecticide on mating, fecundity and development in the bed bug Cimex lectularius L. (Hemiptera: Cimicidae).

Katelyn A. Kowles,Michael F. Potter,Jennifer R. Gordon,Kenneth F. Haynes,Sydney E. Crawley

doi:10.1371/journal.pone.0177410

Abstract

Sublethal exposure to an insecticide may alter insect feeding, mating, oviposition, fecundity, development, and many other life history parameters. Such effects may have population-level consequences that are not apparent in traditional dose-mortality evaluations. Earlier, we found that a routinely used combination insecticide that includes a pyrethroid and a neonicotinoid (Temprid® SC) had deleterious effects on multiple bed bug (Cimex lectularius, L.) behaviors. Here, we demonstrate that sublethal exposure impacts physiology and reproduction as well. We report that sublethal exposure to Temprid SC has variable aberrant effects on bed bugs depending on the strain, including: a reduction in male mating success and delayed oviposition by females. However, after sublethal exposure, egg hatch rate consistently declined in every strain tested, anywhere from 34%-73%. Conversely, impact on fifth instar eclosion time was not significant. While the strains that we tested varied in their respective magnitude of sublethal effects, taken together, these effects could reduce bed bug population growth. These changes in bed bug behavior and fecundity could lead to improved efficacy of Temprid SC in the field, but recovery of impacted bugs must be considered in future studies. Sublethal effects should not be overlooked when evaluating insecticide efficacy, as it is likely that other products may also have indirect effects on population dynamics that could either aid or inhibit successful management of pest populations.

Highlights

Sublethal exposure to an insecticide may affect many life history parameters for insects, including: reductions in feeding or searching time, diminished life span, alterations in development time, and diminished mating and/or fecundity [1,2,3,4,5,6]
We demonstrated a negative impact of sublethal exposure to Temprid SC, the most widely used insecticide for bed bug management in the USA, on bed bug feeding and locomotion, but not on aggregation in daytime harborages [28]
The LT10 values for bed bugs exposed to Temprid SC at the label rate(0.075% a.i., with a 2:1 ratio of imidacloprid, and β- cyfluthrin) differed depending on the initial level of pyrethroid resistance for each strain

Summary

Introduction

Sublethal exposure to an insecticide may affect many life history parameters for insects, including: reductions in feeding or searching time, diminished life span, alterations in development time, and diminished mating and/or fecundity [1,2,3,4,5,6]. Development, mating, fecundity, and feeding after sublethal exposure may have important population-level consequences [8]. Sublethal exposure to a combination product impacts bed bug mating and fecundity standard practice, might overlook population level consequences caused by sublethal effects. Applying the information gleaned from standardized acute toxicity laboratory assays at the population-level can be problematic if there are large differences in the insecticide concentrations or exposure times leading to lethal versus sublethal effects [5]. Since insecticides remain the most common tool for treating infestations [17], understanding both lethal and sublethal effects of pesticides on populations is important

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Results

Conclusion