The Effects of Boric Acid Sugar Bait on Wolbachia Trans-Infected Male Aedes albopictus (ZAP Males®) in Laboratory Conditions

The field release of Wolbachia trans-infected male mosquitoes, as well as the use of toxic sugar baits, is a novel and promising candidate technique for integrated mosquito management programs. However, the methods of action of the two techniques may not be complementary, because the Wolbachia method releases mosquitoes into the environment expecting a wild population reduction in subsequent generations while the toxic baits are intended to reduce the wild population by killing mosquitoes. This laboratory study was conducted to evaluate the effectiveness of boric acid toxic sugar baits on Wolbachia trans-infected male Aedes albopictus, relative to wild-type Ae. albopictus males. Wolbachia trans-infected (ZAP male®) and the wild-type Ae. albopictus males were exposed separately to 1% boric acid in a 10% sucrose solution in BugDorms. In the control test, the two groups were exposed to 10% sucrose solution without boric acid. Percent mortalities were counted for 24 h, 48 h and 72 h post exposure periods. The results show that 1% boric acid toxic sugar bait can effectively kill ZAP males under laboratory conditions, and the effectiveness was significantly higher after 24 h and 48 h, compared to wild-type male Ae. albopictus. This finding will help in planning and coordinating integrated mosquito management programs, including both Wolbachia trans-infected mosquito releases and the use of toxic sugar baits against Ae. albopictus.

Susceptibility of South Texas Aedes aegypti to Pyriproxyfen

An integral part to integrated mosquito management is to ensure chemical products used for area-wide control are effective against a susceptible population of mosquitoes. Prior to conducting an intervention trial using an insect growth regulator, pyriproxyfen, in South Texas to control Aedes aegypti, we conducted a larval bioassay to evaluate baseline levels of susceptibility. We used seven serially-diluted doses ranging from 2.5 ppb to 6.3 × 10−4 ppb. We observed 100% inhibition emergence (IE) at even the lowest dose of 6.3 × 10−4 ppb in our susceptible reference colony of Ae. aegypti Liverpool. In our field strain of Ae. aegypti (F5 colonized from South Texas) we observed 79.8% IE at 6.3 × 10−4 ppb, 17.7% IE at 1.25 × 10−3 ppb, 98.7% IE at 1.25 × 10−2 ppb, and 100% emergence inhibition for the remainder of the doses. Given that commercial pyriproxyfen products are labeled for doses ranging to 50 ppb, we conclude that the field population sampled by this study are susceptible to this insect growth regulator.

FIELD ASSESSMENT OF AUTODISSEMINATION OF PYRIPROXYFEN BY CONTAINER-INHABITING AEDES MOSQUITOES IN FLORIDA

Domestic mosquito control for container-inhabiting Aedes vectors of Zika, chikungunya, yellow fever, and dengue viruses is challenging, and novel methods are needed. Autodissemination strategies are one such method. In this control method, females are attracted to stations treated with an insect growth regulator (IGR), become treated, and subsequently deposit the IGR in natural oviposition sites, preventing pupal emergence. We developed and tested treatment stations in semi-field conditions based on number of captured mosquitoes in the treatment stations. The modified treatment station attracted gravid females with oak leaf infusion and mosquito passage through exit chutes granted access to sucrose and topical contamination of IGR (pyriproxyfen) for 25% of released mosquitoes. Although a majority of released mosquitoes were uncaptured (75%), sufficient amounts of pyriproxyfen contaminated female mosquitoes to result in 75% inhibition of adult emergence in larval bioassays. These stations were then used in a field experiment to test the efficacy using sentinel cups with mosquito larvae. Three treatments which included varied numbers of autodissemination stations (control, low density, and high density) were compared. Both low and high density of stations provided high inhibition of adult emergence from sentinel cups relative to controls. We did not observe differences in mosquito emergence inhibition whether sites contained low or high densities of stations (i.e., similar rates of mosquito inhibition). Two additional field trials showed that topically contaminated mosquitoes were traveling further than expected and causing mortality in sentinel cups at least as far as 80 meters from the autodissemination stations. The development and implementation of autodissemination of IGRs is an additional tool for use in integrated mosquito management.

SEMI-FIELD ULV EVALUATION OF AN ALL-PURPOSE BOTANICAL INSECTICIDE CONTAINING CEDARWOOD AND CINNAMON OILS AGAINST ADULT AEDES AEGYPTI

Public health mosquito control operates with only two classes of mosquito adulticides: pyrethroids and organophosphates. Recent work improving the emulsification of essential oils has increased the potential for development of plantderived active ingredients. There is a growing body of literature on essential oils for various roles in mosquito management. NatureCide Pest Management (NCPM), a product available in private and commercial home pest control, uses a mixture of 25.3% cedarwood oil and 12.7% cinnamon oil as a Federal Insecticide, Fungicide, Rodenticide Act (FIFRA) exempt insecticide for both indoor and outdoor use. Recent investigations by the Anastasia Mosquito Control District of St. Johns County have found other FIFRA exempt products to be effective as a residual spray on vegetation. In continuing the exploration of botanical insecticides, NCPM was used in ULV tests against Aedes aegypti (L.) within its 35-122 ml per L of water label rate. Applications at 35 ml/L resulted in 60-70% knockdown after 1 hr and mortality after 24 hr. Increasing the rate to 70 ml/L resulted in 100% knockdown and mortality across all replications. Crystalline precipitation of the microemulsion was observed in mix tanks after standing for at least 2 wk, but it was not apparent that the efficacy of the product was reduced as a consequence. Cedarwood oil and cinnamon oil are a beneficial combination for ULV adulticiding against mosquitoes and could have a beneficial role for integrated mosquito management.

Larvicidal Activity of Aqueous Pod Extract of Adansonia Digitata (Linnaeus, 1753) on Culex Quinquefasciatus (Say, 1823) Maulik

The study evaluatrd the effect of Baobab, Adansonia digitata pod extract on larvae of Culex quinquefaciatus. The plant material was sun-dried for two weeks and pulverized using mortar and pestle and stored at room temperature for further processes. Powdered plant material was extracted using aqueous cold extraction method. The condensed extract was screened for phytochemicals. Indoor resting adult blood-fed female Culex mosquitoes were collected and introduced into Entomological Cages in the Laboratory and oviposited on water in the bowls. The third instar larvae were confirmed as Cx. quinquefasciatus using Hopkins keys for Culicinae. Triplicates of twenty-five late third instar larvae were tested in pod extract concentrations of 0.5mg/L, 1.0mg/L, 1.5mg/L, 2.0mg/L and 2.50mg/L. Mortality was recorded after 24hr of exposure. The LC50 was determined using probit analysis, while one-way ANOVA was used to establish significant differences in larval mean mortality. Phytochemical constituents such as carbohydrate, cardiac glycosides, steroids, triterpenes, tannins, flavonoids and alkaloids were present. The mean mortality of test concentrations differed significantly (p≤0.05) from control. However, the concentrations: 0.5mg/L and 8.0mg/L had 49% and 71% mortalities, respectively with LC50 of 0.6mg/L. It can be concluded that, the aqueous pod extract of Adansonia digitata demonstrated good activity against Cx. quinquefasciatus. Adansonia digitata pod extracts has potential for controlling larvae of Culex mosquitoes and can be incorporated into integrated mosquito management programme.

The Impact of Hurricane Irma on Our Community and the Collier Mosquito Control District's Mission

ABSTRACT The Collier Mosquito Control District, located in southwest Florida, is uniquely positioned in a subtropical environment between the Gulf of Mexico and Everglades National Park. The District's mission is focused on the control of disease vector and nuisance mosquitoes in Collier County, which is accomplished through integrated mosquito management. Hurricane Irma made landfall in the county on September 10, 2017, leaving in its wake tremendous property and infrastructure damage, and it also disrupted communications and airport operations. These factors greatly affected the District's operations and its ability to meet its mission. In addition, the lengthy loss of electrical power forced most residents outdoors, increasing their exposure to mosquitoes. From challenges in completing poststorm treatments to outdated policies that caught us off-guard, the event prompted a new hurricane policy and plan to ensure improved preparedness for the next natural disaster. The poststorm environment also provided a rich foundation for research into mosquito populations after tropical disturbances of this scale. Here we report the impact on the District's aerial mosquito control operations, changes to internal policies, and mosquito population abundance following Hurricane Irma.