For immediate release.
Media contacts:
Aaron Anderson, Pesticide Program Specialist, Xerces Society, (503)-583-2719, aaron.anderson@xerces.org
Matt Forister, Trevor J. McMinn Professor of Biology, University of Nevada Reno; (775) 784-6770, mforister@unr.edu
PORTLAND, Ore.; December 17, 2025 – A new study published in Stacks Journal has found that backyard mosquito sprays can cause insecticide contamination at levels high enough to kill pollinators, and that these sprays easily travel into neighboring yards. The contamination levels were higher in yards sprayed by private companies than in yards sprayed by local mosquito control districts.
For the study, 26 volunteers in Georgia, Iowa, and Massachusetts placed monitors in their yards before mosquito sprays in their own yard, in a neighboring yard, or by a mosquito control district. This study was conducted by scientists at the Xerces Society for Invertebrate Conservation and the University of Nevada, Reno.
All yards that were sprayed for mosquitoes by private companies had levels of pyrethroid insecticides high enough to kill bees or other beneficial insects, and 75% of samples from yards neighboring those sprayed by private companies had pyrethroid contamination. Pyrethroids are commonly used in residential mosquito sprays and are toxic to pollinators.
“This study is concerning on two counts,” said Aaron Anderson, lead author and pesticide program specialist at the Xerces Society. “One, because in every yard that hired a backyard mosquito spray service, we found insecticides at levels that are going to kill off bees, butterflies, and other valuable insects. Two, because it shows these pesticides don’t stay put where they’re applied and are often going to impact the neighbors’ yards, too.”
On average, yards directly sprayed by private companies had over six times the amount of insecticides lethal to honey bees, with a maximum of over 34 times the lethal dose. Contamination levels in yards neighboring sprayed properties varied from no contamination to levels twice the lethal dose. Sprays by control districts had the lowest levels of residue.
Anderson says the Xerces Society initiated this study in order to respond to the increasing questions they receive about bees and other beneficial insects being killed by nearby pesticide applications.
“We know a lot of people are interested in pollinator gardening and supporting wildlife in their yards. Unfortunately, our results suggest that treating your yard for mosquitoes will likely kill other valuable insects that pollinate fruits and vegetables, feed birds, and keep our neighborhoods healthy”, said Anderson. “The good news is that while neighboring yards do experience some pesticide contamination, with thoughtful action, people can still support pollinators and other wildlife.”
The Xerces Society provides resources on more effective ways to control mosquitoes at home than spraying, which can be shared with neighbors who are considering spraying. When there is an issue between adjoining properties, planting a “drift barrier” of non-flowering shrubs to capture pesticide drift can help protect nearby gardens and wildlife.
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About Xerces Society for Invertebrate Conservation
The Xerces Society for Invertebrate Conservation is a donor-supported nonprofit organization that protects our world through the conservation of invertebrates and their habitats. Xerces works throughout North America to conserve pollinators and other invertebrates, protect endangered species, and reduce pesticide use and impacts.