Influences of Exposure Time and Mortality Assessment Interval on Bioassay Results of Insecticide-Resistant Tropical Bed Bugs (Hemiptera: Cimicidae)

Abstract

We evaluated the influences of insecticide exposure time and mortality assessment intervals on the bioassay results of three insecticide-resistant tropical bed bug Cimex hemipterus (F.) populations (Madam Mo, Tanjong Tokong, and Green Lane). This was achieved using the surface contact method and tested with six commercial insecticide products: Tandem, Temprid SC, Pesguard FG161, Sumithrin, Sumithion, and Phantom applied at label rate on glass petri dishes. Six exposure times (5 min, 10 min, 30 min, 1 h, 4 h, and continuous exposure for 4 or 14 days for Phantom) were tested. A susceptible common bed bug Cimex lectularius L. strain (Monheim) was used as the reference strain as no susceptible C. hemipterus strain exists. In treatment with Temprid SC, the Tanjong Tokong strain showed significantly higher KT50 values at 5, 10, and 30 min exposures than 1 h, 4 h, and continuous exposures. When all resistant populations were evaluated at continuous exposure to Sumithion, they demonstrated moderate resistance levels (RR50 ranged from 6.0 to 7.9), while KT50 and KT95 of other shorter exposure times failed to be generated due to low knockdown rate. Higher mortalities were observed in Tanjong Tokong and Green Lane strains when tested at longer exposure times with Temprid SC, Pesguard FG161, Sumithrin, Sumithion, and Phantom. Better killing effect was observed in the treatment with Temprid SC (Tanjong Tokong and Green Lane strains), Pesguard FG161 (Tanjong Tokong and Green Lane strains), Sumithrin (all C. hemipterus strains), Sumithion (all C. hemipterus strains), and Phantom (all strains tested) at longer mortality assessment intervals. We demonstrated that insecticide exposure time and mortality assessment interval could potentially affect outcomes of product performance evaluations, resulting in underestimation or overestimation of insecticide resistance levels in field populations.

Cuticle thickening associated with fenitrothion and imidacloprid resistance and influence of voltage‐gated sodium channel mutations on pyrethroid resistance in the tropical bed bug, Cimex hemipterus

“…We also noticed that all the three pyrethroid‐resistant C. hemipterus strains (SEL_MY, PEN2_MY, and KUL_MY) carrying the M918I and L1014F mutations were also resistant to fenitrothion and imidacloprid (Table 2). This finding suggests that multiple resistance mechanisms against various classes of insecticides may exist within each population, which was consistent with previous reports 19,33,51 . To understand this further, we investigated if metabolic enzyme activities also contributed to the observed phenomena.…”

“…All modern strains of C. hemipterus are known to display a certain degree of resistance or tolerance to various classes of insecticides when compared with the insecticide‐susceptible C. lectularius Monheim strain, with one exception. Leong et al 33 . recently reported a C. hemipterus Madam Mo strain that was susceptible to pyrethroid.…”

“…Nevertheless, despite the relatively large number of reported putative kdr mutations in C. hemipterus , no pyrethroid‐susceptible genotype has been documented, mainly due to the absence of an established insecticide‐susceptible strain of C. hemipterus . For this reason, all current assessments of insecticide bioassays in C. hemipterus were determined by comparison against the insecticide‐susceptible C. lectularius strains 32,33 …”

Susceptibility of Broflanilide and a Broflanilide-based Insecticide Formulation against the Common Bed Bug, Cimex lectularius L. (Hemiptera: Cimicidae)

“…However, in the field, it may be that bed bugs will not be constantly confined to insecticide treated areas, as the insects harbor in cracks and crevices where insecticide penetration is challenging to achieve. Therefore, the influences of exposure time and mortality assessment interval, as per Leong and colleagues [39], should be investigated in future efficacy studies involving broflanilide. Fortunately, C. lectularius did not avoid surfaces treated with the insecticide, which will ensure a longer exposure with through applications.…”

Potensi Aromaterapi Jeruk Purut (Citrus hystrix DC.) sebagai Adultisida terhadap Aedes aegypti (Linn.) Dewasa

“…Durasi paparan yang singkat hanya mampu menyebabkan nyamuk pingsan dan tidak menimbulkan kematian setelahnya, 40 sedangkan durasi paparan yang lama akan menyebabkan mortalitas lebih tinggi. 46 Oleh karena itu, perlu dilakukan estimasi waktu paparan untuk mendapatkan efektifitas mortalitas yang maksimal. Berdasarkan hal tersebut perlu dilakukan studi lanjutan untuk mengembangkan potensi minyak atsiri jeruk purut sebagai alternatif insektisida terhadap nyamuk Ae.…”