Spatial Repellency Caused by Volatile Pyrethroids is Olfactory-Mediated in the German Cockroach Blattella germanica (Dictyoptera: Blattellidae)

Abstract

Pyrethroids are synthetic insecticides that have a repellent action. This effect has been associated with an increase in the locomotor activity, which causes the avoidance of the insecticide-treated area (excito-repellency). In this work, we studied with behavior and electrophysiological recordings the occurrence of olfactory-mediated repellency caused by pyrethroids of different volatility in the German cockroach Blattella germanica (Linnaeus, 1767). Male cockroaches were spatially repelled when they were exposed to D-allethrin vapors and vapothrin vapors in a dose-dependent manner. No repellency was observed when insects were exposed to permethrin, a non-volatile pyrethroid. To confirm the role of olfaction in this phenomenon, we measured the electrical activity of the cockroaches' antennae in response to these insecticides. There was a significant increase in the electrical activity in response to D-allethrin and vapothrin, but no increase was observed in insects exposed to permethrin. Locomotor activity of cockroaches exposed to pyrethroids was measured in order to discard excito-repellency. No changes in locomotor activity were observed for any of the insecticides. Finally, we found that volatile pyrethroids in the vapor phase cause spatial repellency in cockroaches, being the first report of an olfactory-mediated repellency phenomenon caused by pyrethroids in cockroaches.

Behavioral responses of field‐collected German cockroaches to pyrethroids and pyrethroid‐formulated insecticides

“…found that d‐allethrin and vapothrin vapors spatially repelled German cockroaches while also increasing spontaneous neuronal activity. However, in the same study, permethrin neither spatially repelled nor increased spontaneous electrical activity in the German cockroach 46 . This study confirmed that the vapor pressure (and thus volatility) of pyrethroids plays a major role in determining repellency in German cockroaches.…”

“…Although we tested several pyrethroids and pyrethroid-based products that are commonly used indoors, there are some pyrethroids that have low vapor pressure and high volatility which have been shown to possess true repellent (spatial) properties (e.g., transfluthrin, vapothrin, d-allethrin). [46][47][48][49][50] While much of this work has been done with mosquitoes, a recent study by Boné et al 46 found that d-allethrin and vapothrin vapors spatially repelled German cockroaches while also increasing spontaneous neuronal activity. However, in the same study, permethrin neither…”

Bioallethrin activates specific olfactory sensory neurons and elicits spatial repellency in Aedes aegypti

“…Detection of EAG by bioallethrin is reminiscent of EAG elicited by d ‐allethrin and vapothrin (empenthrin) in the German cockroach 33 . Although it is not yet known if d ‐allethrin‐ or vapothrin‐mediated repellency is dependent on activation of Or(s), we found in this study that bioallethrin repellency is reduced in orco −/− mutant mosquitoes.…”

“…31 In addition, D-allethrin, containing four of the eight stereoisomers of allethrin, and vapothrin, another volatile pyrethroid (also known as empenthrin), have been reported to elicit electroantennogram (EAG) responses from the German cockroach (Blattella germanica). 33 These recent findings prompted us to address the following questions in this study: (i) can bioallethrin elicit non-contact repellency (i.e. spatial repellency) in Ae.…”

“…aegypti antennae 31 . In addition, d ‐allethrin, containing four of the eight stereoisomers of allethrin, and vapothrin, another volatile pyrethroid (also known as empenthrin), have been reported to elicit electroantennogram (EAG) responses from the German cockroach ( Blattella germanica ) 33 …”