Chlorfenapyr and bifenthrin susceptibility monitoring of field collected bed bug populations from the United States
Complete and effective elimination of common bed bug (Cimex lectularius ) infestations continues to be a challenge for the pest management industry. However, effective bed bug control can be achieved through integrated pest management (IPM) programs that use a variety of control techniques. An integral component of an IPM program is the type of insecticide applied. However, insecticide products for bed bug control are somewhat limited as resistance to some pyrethroid insecticides, such as deltamethrin has developed. Currently, chlorfenapyr and bifenthrin are two insecticides approved for bed bug control. Chlorfenapyr is a pro-insecticide from the pyrrole class. Bifenthrin is a type-I pyrethroid that can be applied indoors, but it is also available to the general public and therefore has the potential to be misused for bed bug control. Insecticide resistance is an inevitable consequence of widespread and continuous insecticide application when the proper strategies are not implemented. If bed bugs develop resistance to chlorfenapyr and bifenthrin, it would significantly inhibit the effective management of these notorious pests. Notwithstanding, the susceptibility levels of field bed bug populations to chlorfenapyr and bifenthrin have not been determined on a large scale. Due to the impending threat of insecticide resistance, the primary goal of this research was to screen bed bug populations from across the United States for chlorfenapyr and bifenthrin susceptibility. To screen the field populations , a diagnostic bioassay-based susceptibility monitoring program was developed and implemented. Filter paper and glass vial bioassay methods were compared for different formulations (technical grade and formulated product) of chlorfenapyr and bifenthrin to determine the most suitable assay and formulation for susceptibility monitoring. For each treatment type, lethal concentration (LC50 and LC99) estimates were determined with the insecticide-susceptible Harlan strain. Statistical comparison of PROBIT analysis data for bioassay techniques found significant differences in toxicity ratios at the LC 50 and LC99 levels. Based on the toxicity ratios and bioassay duration, glass vial bioassays using formulated insecticide product appeared more effective for chlorfenapyr and bifenthrin susceptibility monitoring. The glass vial diagnostic LC99 concentrations for chlorfenapyr and bifenthrin were validated using the Harlan-Susceptible and field-collected (Washington D.C. and Richmond, VA) bed bug populations. Subsequently, eight additional field bed bug populations collected from geographically different regions around the U.S. were screened for chlorfenapyr and bifenthrin susceptibility with the diagnostic glass vial assay. Three of the field collected bed bug populations were resistant to chlorfenapyr when compared to the Harlan susceptible strain. Five of the ten populations had significantly different bifenthrin susceptibilities when compared to the Harlan strain at the LC99 concentration. These findings demonstrate the need for continuous susceptibility monitoring of bed bug populations to ensure insecticides remain effective.
Bennett, Purdue University.
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