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Planning Ahead for Mosquito Season

By Aimée Code on 12. June 2017
Aimée Code

Mosquito breeding is well underway in many parts of the country, and every bite stings with the fear of Zika or other mosquito borne illness. It’s understandable why, in the face of a mounting health crisis, communities and health organizations scramble to prevent outbreaks by any means necessary. Spraying may seem like a quick way to soothe the public’s nerves, but as a strategy for controlling mosquitoes it’s a blunt and ineffective tool.


airplane spraying pesticides
To effectively control mosquitoes we need to employ strategies, not sprays.


One hundred fifty years of mosquito management shows that large-scale spraying of pesticides isn’t the most effective option.  Widespread application of adulticides creates a false sense of security while causing many unintended and far-reaching consequences. As municipalities plan for the upcoming mosquito season, they should consider the following:

Early intervention. Larvae are easier to kill than adult mosquitoes since they are contained in water and cannot fly. Furthermore, as larvae, mosquitoes don’t transmit disease. This more targeted treatment has fewer unintended effects in comparison to spraying to kill adult mosquitoes. Still, careful selection of larvicides is also extremely important, as any pesticide can cause unintended consequences.

The Xerces Society has supported targeted use of the biological larvicide Bacillus thuringiensis israelensis (Bti) to control disease transmitting mosquitoes. Bti is relatively targeted in the species it negatively effects – mosquito larvae and a narrow set of other dipterans. Furthermore, it is considered to pose low risk to humans and other mammals. We also support the use of small freshwater crustaceans (cyclopoid copepods), in some settings. Copepods are voracious predators of mosquito larva and occur naturally in many wetlands.

Controlling the spread of disease. All too often people are afraid of mosquitoes even when the mosquitoes in their area either don’t transmit diseases or are not infected. Of the approximately 175 species of mosquitoes in the U.S. only a handful of species are known to transmit disease. By monitoring mosquitoes, residents and public health officials alike can assess actual risk. Having an accurate understanding of risk is very important when fears are running high. Local governments can monitor whether mosquitoes that transmit disease are in the area. If those species are present, the next step is to determine whether they are infected with diseases of concern.

The CDC tracks mosquitoes that vector disease. With the changing climate and the expanded reach of some mosquito species, concerns about mosquito-borne diseases are increasing in the U.S. and around the world. While we are only beginning to understand the effects of Zika, there is a lot known about effective mosquito management. The Centers for Disease Control and Prevention (CDC) and the World Health Organization agree on the application of integrated mosquito management to protect people from mosquito-borne diseases.

Use of adulticides as a last resort. Insecticide treatments to kill adult mosquitoes is not a part of the first line of defense. Trying to kill flying adult mosquitoes is less effective than source reduction. Furthermore, broadcast applications of insecticides over homes and/or natural areas can cause unintended harmful effects. The World Health Organization recommends adulticiding, killing adult mosquitoes, only in case of an outbreak.

For More Information

You can read more about how you can be a part of effective and sustainable mosquito management in your community by reading Xerces’ publication How to Help your Community Create an Effective Mosquito Management Plan. For a comprehensive look at ecologically sound mosquito management techniques, read the Xerces report, Ecologically Sound Mosquito Management in Wetlands.



Aimée Code joined the Xerces Society in 2013 to direct its new pesticide program. In that role, she has built a program focused on securing practices and policies that promote ecologically sound pest management. She and her staff evaluate the risks of pesticides, develop technical guidance, and advocate for actions that reduce reliance on and risks of pesticide use in both urban and agricultural settings. Aimée received her master's of science in environmental health with a minor in toxicology from Oregon State University.

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