Extreme resistance to S-methoprene in field-collected Culex pipiens (Diptera: Culicidae) across the Chicago, IL region.

Insect growth regulators, like S-methoprene, are heavily relied upon worldwide for larval mosquito chemical control due to their target specificity and long-lasting effects. In this study, susceptibility to S-methoprene was evaluated in Culex pipiens, a globally important vector species. Populations from 14 sites throughout the Chicago area with a long history of S-methoprene use and two sites with minimal use in Wisconsin were examined.

Assessment of Truck-Mounted Area-Wide S-methoprene Applications to Manage West Nile Virus Vector Species in the Suburbs of Chicago, IL, USA.

West Nile virus remains the leading cause of arboviral neuroinvasive disease in the United States, despite extensive efforts to control the mosquito vectors involved in transmission. In this study, we evaluated the effectiveness of Altosid SR-20 (active ingredient, S-methoprene 20%) larvicide applications using truck-mounted ultra-low volume (ULV) dispersal equipment to target Culex pipiens Linnaeus (Diptera: Culicidae) and Cx. restuans (Theobald)larvae.

Semi-field and surveillance data define the natural diapause timeline for Culex pipiens across the United States.

Reproductive diapause serves as biological mechanism for many insects, including the mosquito Culex pipiens, to overwinter in temperate climates. While Cx. pipiens diapause has been well-studied in the laboratory, the timing and environmental signals that promote diapause under natural conditions are less understood.

Wide-Area Larviciding with a Buffalo Turbine® Mist Sprayer and Vectolex® WDG.

Wide-Area Larviciding techniques (WALS™) using aqueous suspensions of Bacillus thuringiensis israelensis and various types of mist sprayers have typically been employed against container-inhabiting species of mosquitoes such as Aedes albopictus and Ae. aegypti in urban peridomestic environments. However, relatively little work has been done to examine the use of WALS-applied aqueous suspensions of Lysinibacillus sphaericus (Ls) against susceptible species of mosquitoes in larger natural habitats such as forest pools, floodwaters, and marshes.

Variation in Susceptibility to Permethrin in Culex pipiens and Culex restuans Populations in the Great Lakes Region of the United States.

Two Culex pipiens form Pipiens colony strains and a field population of Cx. restuans from Michigan were susceptible and a Cx. pipiens form Molestus colony strain was comparatively less susceptible to a dose of 43 μg/ml of permethrin in Centers for Disease Control and Prevention (CDC) bottle bioassays.

The Impact of Adulticide on Culex Abundance and Infection Rate in North Shore of Cook County, Illinois.

Mosquito surveillance is critical to reduce the risk of West Nile virus (WNV) transmission to humans. In response to surveillance indicators such as elevated mosquito abundance or increased WNV levels, many mosquito control programs will perform truck-mounted ultra-low volume (ULV) adulticide application to reduce the number of mosquitoes and associated virus transmission. Despite the common use of truck-based ULV adulticiding as a public health measure to reduce WNV prevalence, limited evidence exists to support a role in reducing viral transmission to humans.

Operational Basin Larvicide Evaluations in Northern Cook County, Illinois During 2019 and 2020.

Over the course of 2019 and 2020, 7 larvicide formulations for use in catch basins were evaluated using a standardized pass/fail protocol. A comparison between 1- and 2-pouch doses of VectoLex® water-soluble pouches (WSP; 10 g per pouch) and 20 g of VectoLex FG (loose granules) suggests that the WSP formulation may have a shorter duration than the FG formulation. Results also suggest that 20 g doses of each of 2 larvicides, Duplex™-G and Sumilarv® 0.

Gravid Exhibit A Reduced Susceptibility to Ultra-Low Volume Adult Control Treatments Under Field Conditions.

In July and August of 2018, a field trial was conducted to examine the effectiveness of the North Shore Mosquito Abatement District's operational ultra-low volume (ULV) adulticide program. Two study sites were selected in Skokie, IL, and treated by truck-based ULV with d-phenothrin and prallethrin synergized with piperonyl butoxide over the course of a month. Natural mosquito populations were sampled via Biogents (BG)-counter baited with CO or Alfalfa infusion.

Standardized Back Checks of Catch Basin Larvicides Across Three Modes of Action in the North Shore Suburbs of Chicago, USA.

During June through September 2018, the North Shore Mosquito Abatement District evaluated a quality control protocol for larvicide-treated catch basins that allowed for comparisons of larvicides with different modes of action. Results suggest that when applied at a rate of 2 tablespoons (approximately 20 g of product) per basin, these larvicides (VectoLex FG , Natular™ G30 Spinosad, and Altosid Pellets Methoprene) could reduce the need for retreatment for up to 4 wk or longer. Using this same protocol, Spheratax SPH (50G) was applied to a subset of approximately 900 basins and met the threshold for retreatment 1.

Mosquito adaptations to hematophagia impact pathogen transmission.

Mosquito-borne diseases such as Dengue fever, Chikungunya, and Malaria are critical threats to public health in many parts of the world. Female mosquitoes have evolved multiple adaptive mechanisms to hematophagy, including the ability to efficiently draw and digest blood, as well as the ability to eliminate excess fluids and toxic by-products of blood digestion. Pathogenic agents enter the mosquito digestive tract with the blood meal and need to travel through the midgut and into the hemocele in order to reach the salivary glands and infect a new host.

How micronutrients influence the physiology of mosquitoes.

Micronutrients or non-energetic nutrients (NEN) are needed in reduced amounts, but are essential for many mosquito physiological processes that influence biological traits from vector competence to reproductive capacity. The NEN include amino acids (AA), vitamins, salts, metals and sterols. Free AA plays critical roles controlling most physiological processes, from digestion to reproduction.

Male Aedes aegypti mosquitoes use JH III transferred during copulation to influence previtellogenic ovary physiology and affect the reproductive output of female mosquitoes.

The effect of male accessory gland substances on female reproductive physiology has been previously described as "activating" egg development. However, no mechanism has been described that can explain how male mosquitoes are able to influence egg development in female mosquitoes. To investigate how male mosquitoes are able to influence ovarian physiology and reproductive output we explored three main questions: (1) Do mating and male accessory gland substances affect ovarian physiology and alter markers of oocyte quality during the previtellogenic resting stage? (2) Does the male accessory gland contain JH III and is JH III transferred to the female during copulation? (3) Finally, does the nutritional history of the male affect the amount of JH III transferred to the female and alter reproductive output? By answering these questions it is clear that male mosquitoes are able to alter the female's resource allocation priorities towards reproduction by transferring JH III during copulation; reducing the rate of previtellogenic resorption and increasing the amount of stored ovarian lipids.

Farnesyl phosphatase, a Corpora allata enzyme involved in juvenile hormone biosynthesis in Aedes aegypti.

Background: The juvenile hormones (JHs) are sesquiterpenoid compounds that play a central role in insect reproduction, development and behavior. The late steps of JH III biosynthesis in the mosquito Aedes aegypti involve the hydrolysis of farnesyl pyrophosphate (FPP) to farnesol (FOL), which is then successively oxidized to farnesal and farnesoic acid, methylated to form methyl farnesoate and finally transformed to JH III by a P450 epoxidase. The only recognized FPP phosphatase (FPPase) expressed in the corpora allata (CA) of an insect was recently described in Drosophila melanogaster (DmFPPase).

Aldehyde dehydrogenase 3 converts farnesal into farnesoic acid in the corpora allata of mosquitoes.

The juvenile hormones (JHs) play a central role in insect reproduction, development and behavior. Interrupting JH biosynthesis has long been considered a promising strategy for the development of target-specific insecticides. Using a combination of RNAi, in vivo and in vitro studies we characterized the last unknown biosynthetic enzyme of the JH pathway, a fatty aldehyde dehydrogenase (AaALDH3) that oxidizes farnesal into farnesoic acid (FA) in the corpora allata (CA) of mosquitoes.

The fate of follicles after a blood meal is dependent on previtellogenic nutrition and juvenile hormone in Aedes aegypti.

Juvenile hormone (JH) mediates the relationship between fecundity and nutrition during the gonotrophic cycle of the mosquito in three ways: (1) by regulating initial previtellogenic development, (2) by mediating previtellogenic resorption of follicles and (3) by altering intrinsic previtellogenic follicle "quality", physiology, and competitiveness thereby predetermining the fate of follicles after a blood meal. To support a role for JH in mediating the response of ovarian follicles after a blood meal, we explored three main questions: (1) Do changes in nutrition during the previtellogenic resting stage lead to relevant biochemical and molecular changes in the previtellogenic ovary? (2) Do hormonal manipulations during the previtellogenic resting stage lead to the same biochemical and molecular changes? (3) Does nutrition and hormones during the previtellogenic resting stage affect vitellogenic resorption and reproductive output? We examined the accumulation of neutral lipids in the previtellogenic ovary as well as the previtellogenic expression of genes integral to endocytosis and oocyte development such as the: vitellogenin receptor (AaVgR), lipophorin receptor (AaLpRov), heavy-chain clathrin (AaCHC), and ribosomal protein L32 (rpL32) under various previtellogenic nutritional and hormonal conditions. mRNA abundance and neutral lipid content increased within the previtellogenic ovary as previtellogenic mosquitoes were offered increasing sucrose concentrations.

Nutrient limitation results in juvenile hormone-mediated resorption of previtellogenic ovarian follicles in mosquitoes.

Juvenile hormone (JH) is a central hormonal regulator of previtellogenic development in female Aedes aegypti mosquitoes. JH levels are low at eclosion and increase during the first day after adult emergence. This initial rise in JH is essential for female reproductive maturation.