BASELINE SUSCEPTABILITY AND FIRST OBSERVATION OF KNOCKDOWN RESISTANCE IN AEDES TAENIORHYNCHUS POPULATION OF ST. JOHNS COUNTY, FLORIDA.

The black saltmarsh mosquito, Aedes taeniorhynchus, is a prominent nuisance mosquito within St. Johns County, Florida. Due to their characteristically large outbreaks, and the elevated amount of insecticide application correlated with the outbreaks, local populations of Ae. taeniorhynchus are at an increased risk of developing insecticide resistance. This study was established to form a baseline susceptibility of Ae. taeniorhynchus against two technical grade materials, permethrin, and chlorpyrifos. Centers for Disease Control and Prevention bottle bioassays were conducted with technical-grade materials during two outbreaks in the fall of 2023. Results indicated a baseline susceptibility against the materials tested, but most notably, the phenotypic expression of knockdown resistance (kdr) was observed. Results highlight the need for continued monitoring and investigation into the resistance status and resistance level of this common Florida species.

Interactive Effects of Salinity and Mosquito Larvicides Toxicity to Larvae of Aedes Taeniorhynchus.

Understanding the influence of salinity on the efficacy of mosquito larvicides in brackish water habitats is crucial for effective salt-marsh Aedes taeniorhynchus control. This study investigated the interactive effects of salinity on the toxicity of 3 commonly used mosquito larvicides: Bacillus thuringiensis israelensis (VectoBac® 12AS), spinosad (Natular® SC), and S-methoprene (Altosid® 12AS) against Ae. taeniorhynchus larvae. Four salinity levels (0 ppt [parts per thousand], 8 ppt, 16 ppt, and 32 ppt) were tested in laboratory bioassays. The results revealed distinct responses of these larvicides to varying salinity levels. VectoBac 12AS displayed consistent efficacy across all salinity levels, indicating its suitability for brackish water habitats. In contrast, Natular 2EC exhibited increased effectiveness with higher salinity, making it a preferable choice for saline environments. Altosid 12AS showed its highest efficacy in freshwater, with reduced effectiveness as salinity increased. These findings underscore the need to consider salinity levels when selecting and applying mosquito larvicides in diverse aquatic habitats. Understanding the complex interplay between salinity and larvicide performance is essential for optimizing mosquito control strategies and mitigating mosquito-borne diseases in various environments.

Seasonal Abundance of Aedes Sollicitans and Aedes Taeniorhynchus Related to Temperature, Rainfall and Tidal Levels in Northeastern Florida.

The Anastasia Mosquito Control District, which manages mosquitoes in St. Johns County in northeastern Florida, has observed that the maximum numbers of the salt marsh mosquitoes, Aedes taeniorhynchus and Ae. sollicitan appeared to shift or change relative to each other, as evidenced by the Centers for Disease Control and Prevention (CDC) light trap data in the past 17 years. The aim of this study was to analyze environmental data to identify and explore these changes. Data from CDC light traps, temperature, rainfall, and tidal levels were analyzed using ANOVA. Analyses showed the 2 species had maximum abundance at different temperatures, which translated into seasonal differences with peaks of Ae. taeniorhynchus in the summer and, to a lesser extent, later in the year, and Ae. sollicitans with a peak in the autumn. This seasonal pattern was reflected in rainfall (more rain in autumn than in summer) and also, in the general area, in tidal levels (mean highest tide levels at the recording station were in autumn). The research demonstrated that simplifying the mosquito data, initially using only very high trap numbers (Mean ± 2 SD) that are important for control, identified, and made the seasonal pattern very obvious. The pattern was also observed using all the data but, although significant, was not as clear. Having identified tide as a potential driving variable, further research needs to detail spatial tidal patterns to identify areas and timing of flooding and explore the relationship between salinity and mosquito species and abundance. This is important as sea levels rise and climate changes, both potentially changing the mosquito situation and affecting control actions.

Baseline Susceptibility and Effectiveness of Adulticides to Local Aedes Taeniorhynchus From Collier County, Florida.

The black salt marsh mosquito, Aedes taeniorhynchus, is the primary nuisance mosquito in the coastal regions of Florida. This study aimed to establish the baseline susceptibility of Ae. taeniorhynchus to adulticide products used for mosquito control by the Collier Mosquito Control District (CMCD). The Centers for Disease Control and Prevention bottle bioassay was used to test technical-grade and formulated products, and Merus 3.0® was evaluated in semifield cage trials through aerial applications. The results revealed the baseline susceptibility of Ae. taeniorhynchus to the tested materials and the effectiveness of Merus 3.0 to effectively control the Ae. taeniorhynchus. The study provides important information for the development of an integrated mosquito management strategy for controlling Ae. taeniorhynchus mosquito populations in southwest Florida.

Insecticide Susceptibility Tests of Aedes taeniorhynchus in Yucatan, Mexico.

We report results of susceptibility tests for Aedes taeniorhynchus from 2 localities of Yucatan State, Mexico, to different insecticides. The Centers for Disease Control and Prevention bottle bioassays were performed using the active ingredients of 3 pyrethroids, 2 organophosphates, and 1 carbamate: permethrin (15 µg/ml), deltamethrin (10 µg/ml), alpha-cypermethrin (10 µg/ml), malathion (50 µg/ml), chlorpyrifos (85 µg/ml), and bendiocarb (12.5 µg/ml). The mortality recorded at the diagnostic time of exposure (30 min) was 100% with all insecticides evaluated and for both populations. These results suggest complete susceptibility to the 3 chemical groups generally used for urban Ae. aegypti mosquito control.

A Viability Assessment of Two Commercially Available Sticking Adjuvants Added to a Bifenthrin-Based Barrier Treatment on Aedes taeniorhycnhus.

In an effort to reduce Aedes taeniorhynchus numbers in the northernmost community of Key Largo, FL (known as Ocean Reef), during the peak summer months, Florida Keys Mosquito Control District (FKMCD) has utilized a bifenthrin-based barrier application (Wisdom TC Flowable®) for several years. The FKMCD conducted a study comparing whether 2 aftermarket wetting/sticking adjuvants could improve the efficacy of the barrier treatments used to control Ae. taeniorhynchus. Maximum label rate was used for 3 separate solutions: Wisdom TC Flowable (1 fl oz/gal [7.81 ml/liter] water) with no additives (Wisdom), Wisdom with Lesco Spreader-Sticker® (0.08 fl oz [2.37 ml]), and Wisdom with Xtended Performance® (2.56 fl oz [75.71 ml]). All solutions were applied to 100-ft (approximately 3 m) sections of tree-lined roadways in Key Largo, FL, using a SR 420® Mistblower backpack sprayer (Stihl Corp.). Leaves were collected from each application area for 8 consecutive weeks. Leaves were used to perform leaf bioassays against local populations of Ae. taeniorhynchus adults, and mortality was recorded at 1, 4, and 24 h postexposure. This process was replicated 3 times. Treatments had variable mortality rates at 1, 4, and 24 h postexposure across 7 wk following application. Mortality rates for all mixtures decreased for all exposure times throughout the study. Overall, the Lesco Spreader-Sticker solution was the only combination with a positive significant difference in adult mortality after 24 h.

Population Outbreaks of Mosquitoes After Hurricanes Matthew and Irma and the Control Efforts in St. Johns County, Northeastern Florida.

Major flooding occurred throughout St. John's County, FL, from Hurricane Matthew on October 8, 2016, and Hurricane Irma on September 11, 2017. The flooding caused mosquito population outbreaks in the middle of October in 2016 and September in 2017. Due to the mosquito population outbreaks, Anastasia Mosquito Control District (AMCD) received >3,500 service requests countywide in October 2016 and ≥1,400 service requests in September 2017. During the response to the mosquito population outbreaks caused by the hurricanes, AMCD collaborated with the Emergency Operations Center, Department of Health of St. Johns County, and local media, including television stations, newspapers, and radio stations for public outreach. The AMCD also employed contractors for aerial adulticiding and used every possible resource to successfully control the outbreaks of mosquitoes using both ground and aerial applications.

Screening of natural Wolbachia infection in Aedes aegypti, Aedes taeniorhynchus and Culex quinquefasciatus from Guadeloupe (French West Indies).

Guadeloupe islands are threatened by several mosquito-borne viruses such as Dengue, Chikungunya, Zika and West Nile virus. It appears essential to look for alternative mosquito control methods such as the incompatible insect technique (ITT) aiming at sterilizing wild females by inundative releases of incompatible males. Before considering the implementation of such a strategy, the characterization of genetic diversity of the endocellular bacterium Wolbachia regarding the local mosquito populations is a critical issue. Here, for the first time, we describe the prevalence and diversity of Wolbachia in natural populations of three mosquito species from Guadeloupe: Aedes aegypti, Aedes taeniorhynchus and Culex quinquefasciatus. The detection of Wolbachia in natural Ae. aegypti, Ae. taeniorhynchus and Cx. quinquefasciatus populations was conducted by studying Wolbachia 16S ribosomal RNA gene using a TaqMan quantitative real-time PCR and results were confirmed by conventional PCR and sequencing. In addition, molecular typing of wPip strains in Cx. quinquefasciatus was done by PCR-RFLP. We did not find Wolbachia infection in any of Ae. aegypti and Ae. taeniorhynchus studied populations. Natural Wolbachia infection was detected in Cx. quinquefasciatus with prevalence varying from 79.2% to 95.8%. In addition, no polymorphism was found between the Wolbachia strains infecting Cx. quinquefasciatus specimens, all carrying an infection from the same Wolbachia genetic wPip-I group. These results pave the way for the evaluation of the feasibility of IIT programs to fight against these medically-important mosquito species in Guadeloupe.

Zika Virus Vector Competency of Mosquitoes, Gulf Coast, United States.

Zika virus has recently spread throughout the Americas. Although Aedes aegypti mosquitoes are considered the primary vector, Culex quinquefasciatus and mosquitoes of other species may also be vectors. We tested Cx. quinquefasciatus and Ae. taeniorhynchus mosquitoes from the US Gulf Coast; both were refractory to infection and incapable of transmission.

Pathogenicity Tests on Nine Mosquito Species and Several Non-target Organisms with Strelkovimermis spiculatus (Nemata Mermithidae).

Nine species of mosquitoes and several species of non-target aquatic organisms were tested for susceptibility to the mernaithid nematode, Strelkovimermis spiculatus. All species of Anopheles, Aedes, Culex, and Toxorhynchites exposed to S. spiculatus were susceptible. Of the nine mosquito species tested, C. pipiens quinquefasciatus had the greatest tolerance to initial invasion and the highest percent infection of those that survived. High levels of infection were also achieved with Aedes taeniorhynchus and A. albopictus, but these mosquitoes were significantly less tolerant to parasitism than C. pipiens quinquefasciatus. Strelkovimermis spiculatus did not infect or develop in any of the non-target hosts tested.