Evidence of Tolerance to Silica-Based Desiccant Dusts in a Pyrethroid-Resistant Strain of Cimex lectularius (Hemiptera: Cimicidae)

Abstract

Insecticide resistance in bed bugs (Cimex lectularius and Cimex hemipterus) has become widespread, which has necessitated the development of new IPM (Integrated Pest Management) strategies and products for the eradication of infestations. Two promising options are the diatomaceous earth and silica gel-based desiccant dusts, both of which induce dehydration and eventual death upon bed bugs exposed to these products. However, the impact of underlying mechanisms that confer resistance to insecticides, such as cuticle thickening, on the performance of these dusts has yet to be determined. In the present study, two desiccant dusts, CimeXa Insecticide Dust (silica gel) and Bed Bug Killer Powder (diatomaceous earth) were evaluated against two strains of C. lectularius; one highly pyrethroid-resistant and one insecticide-susceptible. Label-rate doses of both products produced 100% mortality in both strains, albeit over dissimilar time-frames (3–4 days with CimeXa vs. 14 days with Bed Bug Killer). Sub-label rate exposure to CimeXa indicated that the pyrethroid-resistant strain possessed a degree of tolerance to this product, surviving 50% longer than the susceptible strain. This is the first study to suggest that mechanisms conferring resistance to pyrethroids, such as cuticular thickening, may have potential secondary impacts on non-synthetic insecticides, including desiccant dusts, which target the bed bug’s cuticle.

Insecticide resistance and resistance mechanisms in bed bugs, Cimex spp. (Hemiptera: Cimicidae)

“…Penetration resistance also works in combination with other resistance mechanism(s), as it has been hypothesized that decreased cuticular penetration could help to ‘buy more time’ for detoxifying enzymes to metabolize the insecticide or to allow the insect to excrete the insecticide before it reaches its target [90, 98]. Penetration resistance has been reported in various insect pests, including the house fly Musca domestica (L.) [98–100], the German cockroach B. germanica [2, 101], the dengue mosquito Aedes aegypti (L.) [102], and the common bed bug, C. lectularius [94, 95, 103]. …”

Behavioral Responses of the Common Bed Bug, Cimex lectularius, to Insecticide Dusts

“…Diatomaceous earth has been perceived as less toxic to mammals and a more sound option for bed bug control [ 20 , 40 , 41 ]. Several laboratory studies have reported high efficacy of DE against bed bugs [ 29 , 31 , 42 ].…”

“…These responses might be behavioral adaptations that would decrease the pickup of dust particles [ 33 ]. In addition, a recent study reported that a multiresistant bed bug population with cuticular thickening exhibited tolerance to sublabel rates of silica gel-based dusts (CimeXa) [ 41 ]. These findings are worrisome given the fact that these mechanisms might confer cross resistance across other nonrelated insecticides.…”

Evaluation of a Non-Chemical Compared to a Non-Chemical Plus Silica Gel Approach to Bed Bug Management

“…When bed bugs were exposed to CimeXa insecticide dust during a choice bioassay and a forced-exposure bioassay, 95% mortality was achieved after 1 day, and 100% mortality was observed after 5 and 10 days [ 20 ]. In another laboratory study, CimeXa insecticide dust at the label rate produced 100% mortality in highly pyrethroid-resistant and insecticide-susceptible strains of bed bugs within 3–4 days [ 21 ]. Ninety-eight percent mortality was achieved after 1 day when silica gel dust, in a water solution, was applied to bed bugs that were moderately resistant to pyrethroids [ 22 ].…”