Effectively Treating Container Mosquito Species with WALS® Applications of VectoBac® WDG

With insecticide resistance remaining on the forefront of operational mosquito control districts all over, it is important to implement resistance management strategies. Constant surveillance of current insecticide resistance levels in your local mosquito control populations ensures effective control.  Aedes aegypti resistance in Florida is nothing new. Genetic and phenotypic studies have shown that local populations throughout the state have decreasing susceptibility levels to a variety of adulticides. With a limited toolbox of products to choose from, product rotation can be somewhat challenging. Monitoring the efficacy of available adulticides and larvicide products, and application methods in field trials, can give us key insights into the efficacy of a specific product against a specific population.

With the prevalence of mosquito insecticide resistance, finding effective control strategies is extremely vital to having a successful integrated pest management program.

Take a look at this trial that was conducted in Manatee County Florida in order to address these resistance issues by applying a biological larvicide to target a resistant strain of Aedes aegypti in Cortez, Florida:

2020 WALS Evaluation

In the summer of 2020, Manatee County Mosquito Control in Palmetto, FL evaluated WALS strategy with the truck-mounted A1 Super Duty Mist Sprayer and VectoBac WDG against Aedes aegypti at 0.5 lb/acre.  The study was conducted in Cortez (Manatee County), Florida, USA (27° 27’ N, 82° 40’ W). The first study site was the untreated control, which was 55 acres, and the second study site was the treatment site which was 57 acres. These locations were chosen because historical data has shown high populations of Ae. aegypti based on weekly ovitrap surveillance. Weekly BGs and ovitraps (10–15 traps/site) were deployed to monitor adult population dynamics. A total of 50 bioassay jars were placed in the field each afternoon of the Bti application (8 application events) at fixed locations to collect droplets and gauge efficacy. There was significant reduction in female adults (P = 0.0002) and landing rate counts (P = 0.0058) as a result of treatment. Larval bioassays during the eight applications confirmed Bti deposit in a variety of coverage types regardless of placement in the yards.

Data provided by Katie Williams, Technical Development Specialist at ADAPCO, previous Senior Research Biologist at Manatee County Mosquito Control District.

Fig. 1 Aerial overview of experimental sites in Cortez, Florida, Manatee County. Top Left: Control site larval jar locations. Top Right: Treatment site larval jar locations. Bottom Left: Control site surveillance locations with ovitraps and BG Sentinel 2 Traps.  Bottom Right: Treatment site surveillance locations with ovitraps and BG Sentinel 2 Traps.

Fig.2 Sampling location coverage type in the treatment site.

From top to bottom:

  • (E) Exposed to sky
  • (S) sparse vegetation cover
  • (D) dense vegetation cover
  • (C) covered (obstructed from sky)

Fig.3 Percent larval Mortality (±SE) one-way analysis of variance (ANOVA): L2/L3 Aedes aegypti larval bioassays after weekly/bi-weekly A1 Mister & VectoBac WDG applications during May-August 2020, Manatee County, Florida.

Fig. 4 Average females caught in BGS traps for each week for untreated control and WALS sites.

Fig. 5 Average number of females collected (Landing Rate Count, LRC) for each week in untreated control and WALS sites.

VectoBac WDG
A1 Super Duty Mist Sprayer

Container species such as Aedes aegypti and Aedes albopictus are a major source of concern for mosquito abatement agencies across the globe due to their high vectorial capacity. In addition, adulticiding these species can be quite difficult because of their preference for host seeking and oviposition in the daytime. Various application methods of VectoBac WDG complement integrated vector management (IVM) programs that are aimed at reducing these species that have the capacity to transmit dengue, chikungunya, and yellow fever, as well as other arboviruses.

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