Bioefficacy Evaluation of Commercial Mosquito Coils Containing Metofluthrin, d-Allethrin, d-Trans Allethrin, and Prallethrin Against Aedes albopictus (Diptera: Culicidae) in Malaysia

A volatilized pyrethroid insecticide from a mosquito repelling device does not impact honey bee foraging and recruitment

Because nontarget, beneficials, like insect pollinators, may be exposed unintentionally to insecticides, it is important to evaluate the impact of chemical controls on the behaviors performed by insect pollinators in field trials. Here we examine the impact of a portable mosquito repeller, which emits prallethrin, a pyrethroid insecticide, on honey bee foraging and recruitment using a blinded, randomized, paired, parallel group trial. We found no significant effect of the volatilized insecticide on foraging frequency (our primary outcome), waggle dance propensity, waggle dance frequency, and feeder persistency (our secondary outcomes), even though an additional deposition study confirmed that the treatment device was performing appropriately. These results may be useful to consumers that are interested in repelling mosquitos, but also concerned about potential consequences to beneficial insects, such as honey bees.

Evaluation of An Aerial Application of Duet Hd® Against Aedes Dorsalis and Culex Tarsalis in Rural Habitats of the Great Salt Lake, Utah

The Salt Lake City Mosquito Abatement District (SLCMAD) has been conducting aerial applications using an organophosphate insecticide against adult mosquitoes for several decades. In order to evaluate a potential rotation product, aerial applications of Duet HD™, a pyrethroid, were conducted under operational conditions against wild populations of Aedes dorsalis and Culex tarsalis and against colony strains of Cx. pipiens and Cx. quinquefasciatus. The erratic wind patterns of the greater Salt Lake area did not prevent sufficient droplet deposition flux at 9 monitoring locations spread across a 5,120-acre (2,072 ha) spray block within rural habitats. Three separate aerial application trials showed great efficacy against Ae. dorsalis. In contrast, Cx. tarsalis exhibited inconsistent treatment-associated mortalities, suggesting the presence of less susceptible or resistant field populations as a result of spillover from agricultural or residential pyrethroid usage. Bottle bioassays to diagnose pyrethroid resistance using field-collected Cx. tarsalis indicated that some populations of this species, especially those closest to urban edges, failed to show adequate mortality in resistance assays. Despite challenging weather conditions, Duet HD worked reasonably well against susceptible mosquito species, and it may provide a crucial role as an alternative for organophosphate applications within specific and sensitive areas. However, its area-wide adoption into control applications by the SLCMAD could be problematic due to reduced impacts on the most important arboviral vector species, Cx. tarsalis, in this area. This study demonstrates the importance of testing mosquito control products under different operational environments and against potentially resistant mosquito populations by municipal mosquito control districts.

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

BACKGROUND

Use of pyrethroid insecticides is a pivotal strategy for mosquito control globally. Commonly known for their insecticidal activity by acting on voltage-gated sodium channels, pyrethroids, such as bioallethrin and transfluthrin, are used in mosquito coils, emanators and other vaporizers to repel mosquitoes and other biting arthropods. However, whether specific olfactory receptor neurons are activated by pyrethroids to trigger spatial repellency remains unknown.

RESULTS

We used behavioral and electrophysiological approaches to elucidate the mechanism of bioallethrin repellency in Aedes aegypti, a major vector of dengue, yellow fever, Zika and chikungunya viruses. We found that bioallethrin elicits spatial (i.e. non-contact) repellency and activates a specific type of olfactory receptor neuron in mosquito antennae. Furthermore, bioallethrin repellency is significantly reduced in a mosquito mutant of Orco, an obligate olfactory co-receptor that is essential for the function of odorant receptors (Ors). These results indicate that activation of specific Or(s) by bioallethrin contributes to bioallethrin repellency. In addition, bioallethrin repellency was reduced in a pyrethroid-resistant strain that carries two mutations in the sodium channel gene that are responsible for knockdown resistance (kdr) to pyrethroids, indicating a role of activation of sodium channels in bioallethrin repellency.

CONCLUSION

Results from this study show that bioallethrin repellency is likely to be the result of co-activation of Or(s) and sodium channels. These findings not only contribute to our understanding of the modes of action of volatile pyrethroids in spatial repellency, but also provide a framework for developing new repellents based on the dual-target mechanism revealed. © 2021 Society of Chemical Industry.

Efficacy of orally toxic sugar baits against contact-insecticide resistant culex quinquefasciatus

In recent years, attractive toxic sugar bait has been used in the mosquito control in nature, and achieved good control effects. However, the current researches about toxic sugar bait did not focus on whether the wild mosquito population used for control is resistant or not. The purpose of this study was to evaluate the effectiveness of the toxic sugar bait against mosquito resistant populations to test the effects of bait on the control of mosquitoes with different levels of resistance. Boric acid, dinotefuran and deltamethrin were separately formulated into toxic sugar bait to test their anti-mosquito activity against Culex quinquefasciatus. Using the sugar baits formulated with boric acid and dinotefuran, the mortality of Cx. quinquefasciatus resistant populations was significantly higher than that of sensitive populations at the same concentration. Conversely, with the use of sugar baits formulated with deltamethrin, the mortality of Cx. quinquefasciatus resistant populations was significantly lower than that of sensitive populations at the same concentration. The results suggested that toxic sugar baits might have a good application prospect in high resistant mosquito management.