Visualizing efficacy of pesticides against disease vector mosquitoes in the field

Authors: Gibson, Seth; Linthicum, Kenneth - Ken; Aldridge, Robert; Golden, Frances; WALKER, TODD - East Baton Rouge Parish Mosquito Abatement And Rodent Control

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2018
Publication Date: 3/16/2019
Citation: Britch, S.C., Linthicum, K., Aldridge, R.L., Golden, F.V., Walker, T.W. 2019. Visualizing efficacy of pesticides against disease vector mosquitoes in the field. Journal of Visualized Experiments. 145:e58440. https://doi.org/10.3791/58440.
DOI: https://doi.org/10.3791/58440

Interpretive Summary: Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform across desert, tropical, temperate, or urban ecological zones. We designed a system of protocols to support efficient, cost-effective, portable, and standardized evaluation of aerosol adulticide and larvicide techniques with diverse combinations of pesticides and equipment across multiple environments. At the core of these protocols is the use of colony-reared sentinel mosquitoes (adults and immatures) or sand flies (adults) to indicate spatial and temporal patterns of pesticide efficacy. In the case of adulticide applications, sentinel adult mosquitoes or sand flies are contained in small single-use disposable cages distributed in structured arrays through the target area and an untreated control area. For larvicide applications, small single-use disposable cups are similarly distributed to collect sprayed larvicide droplets for later introduction of water and sentinel colony-reared immature mosquitoes. We record percent mortality in sentinel cages, or percent adult development in sentinel cups, at set intervals post-spray and use these data to produce maps of efficacy that may be quantitatively compared between and among environments.

Technical Abstract: Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform across desert, tropical, temperate, or urban ecological zones. Certain species of these three groups of insects are important vectors of parasites, viruses, filarial worms, and bacteria that cause significant diseases in humans, pets, and livestock worldwide. To best protect public and veterinary health from these insects, the environmental limitations of pesticides need to be investigated to inform effective use of the most appropriate pesticide formulations. Public health pesticide manufacturers are not required by the US Environmental Protection Agency to specify expected efficacy of a formulation across a range of environments, yet these pesticides are in operational use for mosquito and vector control across multiple ecological zones in the US and around the world. We developed a research program to evaluate an array of combinations of pesticides and pesticide application equipment and techniques in hot-arid desert, hot-humid tropical, warm and cool temperate, and urban locations to derive pesticide use guidelines specific to target insect and environment. In this program we evaluate pesticides that target adult stages of mosquitoes and sand flies (adulticides) and immature stages of mosquitoes (larvicides) using pesticide application equipment that is hand carried, truck or aircraft mounted, and installed in fixed locations. We evaluate four major outdoor pesticide application techniques: (1) ultra-low volume (ULV) or thermal fog aerosol space sprays of adulticides designed for rapid knockdown of target insects, (2) a variant of the first technique where liquid larvicides are applied with ULV or thermal fog for short or long term suppression of immature stages of target insects, (3) timed misting sprays from fixed locations designed to repel or kill, and (4) low volume (LV) cold mist sprays of residual pesticides designed to apply long lasting toxic or repellent coatings on a variety of natural or artificial substrates. We here present detailed methods for conducting techniques (1) and (2). Methods for techniques (3) and (4) are described in brief in earlier publications.