Ultra-low volume application of spinosad (Natular 2EC) as a residual in a hot-arid environment against Aedes aegypti

Authors: Golden, Frances; Gibson, Seth; Linthicum, Kenneth - Ken; Aldridge, Robert; WITTIE, JEREMY - Coachella Valley Mosquito And Vector Control District; GUTIERREZ, ARTURO - Coachella Valley Mosquito And Vector Control District; SNELLING, MELISSA - Coachella Valley Mosquito And Vector Control District; HENKE, JENNIFER - Coachella Valley Mosquito And Vector Control District

Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2018
Publication Date: 3/28/2018
Citation: Golden, F.V., Britch, S.C., Linthicum, K., Aldridge, R.L., Wittie, J., Gutierrez, A., Snelling, M., Henke, J. 2018. Ultra-low volume application of spinosad (Natular 2EC) as a residual in a hot-arid environment against Aedes aegypti. Journal of the American Mosquito Control Association. 34(1):63-66. doi:10.2987/17-6703.1.
DOI: https://doi.org/10.2987/17-6703.1

Interpretive Summary: The Aedes aegypti mosquito is a very important public health threat because it can be responsible for spreading illnesses such as dengue, Zika, and chikungunya. Control of larval Aedes aegypti mosquitoes is very difficult, as this mosquito lays eggs and develops in very small sources of water that can be plentiful in typical yards. These water sources, which can include sources as small as a puddle created by a crumpled tarp or a bottle cap, are extremely hard to reach with larvicide formulations. By the time these water sources are identified and sprayed with larvicides, adult mosquitoes may already be in production. Additionally, in hot and dry environments, mosquitoes rest and lay eggs near homes, where they can be protected from the extreme temperatures and dryness of the larger environment. Any larvicide sprays need to move through the larger environment and its variable plant coverage, and reach the mosquitoes and their breeding sites where they are. We conducted a study in a hot, dry area of the Coachella Valley in southern California to investigate the possibility that a biologically-based larvicide called spinosyn could be sprayed through vegetation and reach small, dry containers that could hold water after a rain. We hypothesized that this formulation could be used to spray areas harboring likely Aedes aegypti larval habitat well before the pockets collect water and so could improve integrated vector management programs. We found that the formulation applied in this way was somewhat efficacious against Aedes aegypti, but not as efficacious as an adulticide. We believe that further study is necessary to determine if it is truly efficacious to apply the larvicide in this way.

Technical Abstract: We investigated the efficacy of a biologically-based larvicide, Natular 2EC, against Aedes aegypti in a hot-arid environment when applied with a backpack ULV sprayer. We deployed empty plastic sentinel cups in a variety of locations with greater or lesser vegetation cover. After spray applications, the sentinel cups were collected and capped. Upon returning to the laboratory, water and 50 colony-reared Ae. aegypti larvae were added to each cup. Larval mortality was determined by counting the number of adults that successfully emerged from each cup. Our results show a new potential for a residual effect when using Natular 2EC.