Impact of the Insect Growth Regulator Pyriproxyfen on Immature Development, Fecundity, and Fertility of Aedes albopictus

Assessment of barrier treatments impacting Aedes albopictus (diptera: culicidae) using lambda-cyhalothrin and pyriproxyfen in a suburban neighborhood in Eastern North Carolina, 2018

Pyrethroids are commonly used in barrier treatments but less is known about how mosquitoes are affected by the simultaneous application of an insect growth regulator (i.e., pyriproxyfen) used in barrier treatments. This field study, conducted from May 14 - October 16, 2018, evaluated the effect of lambda-cyhalothrin (pyrethroid adulticide) and pyriproxyfen on the reproduction (measured by fecundity and adult emergence) and abundance of Aedes albopictus. Nine properties were treated with Demand®CS 0.06% + Archer® 0.010% (every 60 days) and three control properties received no treatment (N=12 total properties). No significant (P>0.05) differences were observed between abundance of Ae. albopictus in treatment compared to control groups. However, significant differences were observed in abundance of Ae. albopictus adults between weeks at both control (P = 0.003) and treatment (P < 0.0001) properties. Results from our research show that continued studies are needed to determine the efficacy of barrier treatments for this species.           .

Indirect transfer of pyriproxyfen to European honeybees via an autodissemination approach

The frequency of arboviral disease epidemics is increasing and vector control remains the primary mechanism to limit arboviral transmission. Container inhabiting mosquitoes such as Aedes albopictus and Aedes aegypti are the primary vectors of dengue, chikungunya, and Zika viruses. Current vector control methods for these species are often ineffective, suggesting the need for novel control approaches. A proposed novel approach is autodissemination of insect growth regulators (IGRs). The advantage of autodissemination approaches is small amounts of active ingredients compared to traditional insecticide applications are used to impact mosquito populations. While the direct targeting of cryptic locations via autodissemination seems like a significant advantage over large scale applications of insecticides, this approach could actually affect nontarget organisms by delivering these highly potent long lasting growth inhibitors such as pyriproxyfen (PPF) to the exact locations that other beneficial insects visit, such as a nectar source. Here we tested the hypothesis that PPF treated male Ae. albopictus will contaminate nectar sources, which results in the indirect transfer of PPF to European honey bees (Apis mellifera). We performed bioassays, fluorescent imaging, and mass spectrometry on insect and artificial nectar source materials to examine for intra- and interspecific transfer of PPF. Data suggests there is direct transfer of PPF from Ae. albopictus PPF treated males and indirect transfer of PPF to A. mellifera from artificial nectar sources. In addition, we show a reduction in fecundity in Ae. albopictus and Drosophila melanogaster when exposed to sublethal doses of PPF. The observed transfer of PPF to A. mellifera suggests the need for further investigation of autodissemination approaches in a more field like setting to examine for risks to insect pollinators.

Autodissemination approaches have attracted a significant amount of attention for mosquito control because of the advantages of self-delivery of small amounts of highly potent insect growth regulators (IGRs) such as pyriproxyfen (PPF) to oviposition locations. However, while PPF may be delivered to oviposition locations by the mosquito vehicles, these treated mosquitoes may also be delivering PPF to nectar sources that other insects may visit, in particular important insect pollinators. Here we have examined for the direct transfer of PPF to nectar sources and the indirect transfer to the European honey bee. We show PPF is being deposited on artificial nectar sources and is being indirectly transferred to European honey bees. The results are discussed in reference to the potential risks to important insect pollinators of using autodissemination approaches for mosquito control.

Evaluation of a mosquito home system for controlling Aedes aegypti

BACKGROUND

Dengue is a significant public health issue that is caused by Aedes spp. mosquitoes. The current vector control methods are unable to effectively reduce Aedes populations and thus fail to decrease dengue transmission. Hence, there is an urgent need for new tools and strategies to reduce dengue transmission in a wide range of settings. In this study, the Mosquito Home System (MHS) and Mosquito Home Aqua (MHAQ) formulations were assessed as commercial autodissemination traps in laboratory and small-scale field trials.

METHOD

Multiple series of laboratory and small-scale field trials were performed to assess the efficacy of MHS and MHAQ exposed to Ae. aegypti. In the laboratory trials, various parameters such as fecundity, fertility, wing size, oviposition preferences, residual effects, and MHAQ transference to other containers through controlled experiments were tested. For small-scale field trials, the efficacy of the MHS and MHAQ approaches was determined to ascertain whether wild mosquitoes could transfer the MHAQ formulation from MHS stations to ovitraps.

RESULTS

The data revealed that Ae. aegypti was highly susceptible to low concentrations of MHAQ formulations and had a residual effect of up to 3 months, with MHAQ exposure affecting fecundity, fertility, and mosquito wing size. In the oviposition studies, gravid females strongly preferred the hay infusion compared to tap water and MHAQ during egg-laying in the laboratory. Nevertheless, the use of commercial MHAQ by MHS was highly attractive in field settings compared to conventional ovitraps among local Aedes spp. mosquitoes. In addition, MHAQ horizontal transfer activities in the laboratory and small-scale field trials were demonstrated through larval bioassays. These findings demonstrated the potential of MHAQ to be transferred to new containers in each study site.

CONCLUSION

This study provided proof of principle for the autodissemination of MHAQ. Through further refinement, this technique and device could become an effective oviposition trap and offer an alternative preventive tool for vector control management.