A Novel Simulated-Use Test for Determining the Efficacy of Insecticides Against Bed Bugs (Hemiptera: Cimicidae)

Abstract

The common bed bug Cimex lectularius L. has undergone a worldwide expansion in recent years, due to increased opportunities for dispersal and development of insecticide resistance. For successful control, efficacy testing of products against bed bugs and determination of insecticide resistance under practical conditions are of outstanding importance. A new test system mimicking the practical use situation of residual insecticides was developed and evaluated. Bed bugs were attracted by CO2 and heat to cross surfaces treated with alpha-cypermethrin and bendiocarb. In contrast to the complete efficacy of alpha-cypermethrin (less than 1% surviving bed bugs [with one exception of 5%]), only 45.3, 46, and 29% of insecticide-susceptible bed bugs showed lethal damage 7 d after contact with freshly bendiocarb-treated wallpaper or insecticide aged for 1 or 2 wk. Results show that the efficacy of different insecticides can be assessed with this new test system. Moreover, susceptibility to deltamethrin of five bed bug field strains, collected from infested apartments in Berlin, Germany, was determined in a filter paper contact bioassay. Resistance ratios (RRs) ranged between 4.3 and 20.7. In the novel simulated-use test, efficacy of alpha-cypermethrin was tested against the bed bug strain with the highest RR. In contrast to the insecticide-susceptible laboratory strain, alpha-cypermethrin was not effective against the field strain, where 26–50% of the bed bugs survived and even laid eggs. These results provide evidence for the presence of practically relevant pyrethroid resistance in bed bugs in Germany.

Detection of target-site and metabolic resistance to pyrethroids in the bed bug Cimex lectularius in Berlin, Germany

“…S1 ). Except for the SK strain (collected from four separate infested sites ( Vander Pan et al, 2019 )) all strains originated from individual infested locations. Bed bugs from the different collection sites were identified as C. lectularius using the taxonomic key in , specifically the pronotum width-to-length ratio.…”

“…Sequences from the vssc cDNA obtained for all strains that were successfully bred showed >99.5% identity to C. lectularius and <97% identity to C. hemipterus , which confirmed the morphological identification. The C. lectularius strain of the German Environment Agency (UBA) was used as an insecticide susceptible reference strain ( Vander Pan et al, 2019 ).…”

“…Except for the SK strain (collected from four separate infested sites ( Vander Pan et al, 2019) ), all strains originated from individual infested locations. The UBA strain was used as an insecticide susceptible reference strain ( Vander Pan et al, 2019 ). Strain/population Laboratory rearing Pyrosequencing 5 technical replicates RT-qPCR 2 technical replicates pooled bed bugs individual bed bugs individual bed bugs UBA since 1947 100 M a /100 F b 10 M/10 F 10 M SK 6 generations 100 M/100 F 10 M/10 F 10 M OB LB AS HO GW 2 generations 75 M/75 F n.a.…”

“…In the EU, most of the authorized products contain pyrethroids, which are primarily used for bed bug control ( Kilpinen et al, 2011 ; Davies et al, 2012 ; Dang et al, 2017 ; Gonzalez-Morales and Romero, 2019 ). Pyrethroid resistance in bed bugs has been described in many countries ( Booth et al, 2015 ; Palenchar et al, 2015 ; Dang et al, 2017 ; Balvin and Booth, 2018 ; Caceres et al, 2019 ; Holleman et al, 2019 ; Vander Pan et al, 2019 ). German pest control companies have also observed increasing difficulties in controlling bed bugs with pyrethroids (personal communications with pest controllers).…”

“…Additionally, relative mRNA expression levels of the four CYP genes cyp397a1 , cyp398a1 , cyp4cm1, and cyp6dn1 were determined using reverse transcription quantitative PCR (RT-qPCR). In a first step, the molecular assays were validated using five C. lectularius field strains of which the resistance ratios for deltamethrin had been determined in a previous study ( Vander Pan et al, 2019 ). In a second step, the validated molecular assays were used to examine 15 additional field-collected strains.…”