We have a range of information and links to further reading on our Controlling Mosquitoes page that should be helpful. Below is information our entomologist has provided for similar queries we've received in recent years (it includes some tips for mitigating spray impacts if someone is not successful and neighbors wind-up having their yards sprayed):

Researchers with the Xerces Society for Invertebrate Conservation recently completed a study in which they sampled insecticide residues in backyards that were sprayed for mosquitoes, as well as in adjacent yards. They found that neighboring yards had an average residue level equal to 0.12 times the LD50 (the Lethal Dose that kills 50% of a honeybee test population), compared to an average of 6.6 times the LD50 in yards that were directly sprayed. This indicates that while insecticide levels are lower in neighboring yards, there is still potential acute risk to pollinators. One of the researchers recently presented a webinar on this work if you would like to learn more: The Truth About Mosquito Sprays: Investigating their Impact on Pollinators.

The current general consensus is that having neighbors who spray for mosquitoes should not prevent you from creating or maintaining pollinator habitat. However, there are several steps you can consider/take to help minimize potential impacts:

• Place pollinator habitat as far as possible from direct spray areas. Position plantings closer to your home and farther from property boundaries where drift is more likely.
• Use vegetation or physical barriers to reduce drift. Planting tall, coniferous shrubs or trees (needled evergreens), such as members of the Cupressaceae family (junipers, arborvitae, cedars) or genus like Pinus (pines), Picea (spruces), Abies (firs), and Taxus (yews), can help buffer your habitat. Buffers should ideally be semi-permeable (around 50% porosity), meaning you should still be able to see through the buffer; this allows air to pass through and filter pesticide particles. If vegetation or structures are too dense, they can force air and spray drift upward, leaving the air unfiltered and allowing drift to continue beyond the buffer zone. Fencing and other porous physical barriers can also be used.
• Add clear habitat signage. Visible signs can alter/remind neighbors of your pollinator garden and may inspire interest and conversation.
• Contact the spray companies your neighbors use. Some people have reported success by calling these companies ahead of a spray and requesting the use of drift-reducing spray nozzles that create larger, coarser droplets. After such requests, some have observed applicators using more caution, but this can vary.
• Communicate with your neighbors when possible. While this depends on the relationship, even simply letting your neighbors know you have a pollinator garden can encourage them to pass this information to their spray companies. They may adjust their practices or avoid spraying near your habitat. Positive, curiosity-driven conversations, rather than accusatory ones, can be more effective. Visible native plantings and habitat signs near the front yard can also help spark interest among neighbors and passersby.

It is important to remember that no one can eliminate every risk to pollinators. However, creating habitat, so long as it is not directly sprayed with pesticides, still provides valuable refuge for many pollinators and beneficial insects (regardless of habitat size). As more studies emerge, we will continue to learn how best to reduce the impacts of mosquito-control sprays in the future.

Miri