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Coping With High Mosquito Activity: A Guide to What Works and What Doesn't

Mosquito Activity at All-Time High

If you live along the southeast or northern edges of the city or spend time outdoors in these parts of town, you know firsthand that this year has had record-breaking mosquito activity. The entire region has seen a spike in mosquito activity that began last year and has continued into this season. The City of Boulder, along with Boulder County and other cities and counties throughout the Front Range, have comprehensive mosquito management programs in place. Yet, mosquito numbers remain far above average.

Plenty of moisture and hot weather have provided perfect conditions for mosquitoes. But these factors alone don’t explain the high mosquito populations or what the underlying causes might be for these changes. City ecologists are gathering data and information to try to better understand the factors that could be contributing to increased mosquito activity and are consulting with subject matter experts. This information will be used to explore additional strategies to manage mosquitoes as the city updates and improves its mosquito management program.

Coping with High Mosquito Activity

There are several products on the market that claim to reduce mosquitoes or prevent bites. It’s important to know what is and isn’t effective.

What doesn’t work

  • Bug zappers - A University of Florida scientist, Jonathan Day, says that bug zappers can cause more harm than good. They can attract more mosquitoes to your yard and kill harmless or beneficial insects that help control pests. In a study, only eight mosquitoes were caught of the 10,000 insects killed in one night by a bug zapper.
  • Sonic devices/application – There are a number of ultrasonic devices and mobile applications that claim to use sound to repel mosquitoes. There is no evidence that any of them work.
  • Citronella candles – Studies have shown that citronella candles do not reduce mosquito bites.

What does work

  • Effective Repellents/Bug Spray – Products containing DEET, oil of lemon eucalyptus, picaridin or IR 5353 are all effective at repelling mosquitoes. Make sure that you follow the label directions and reapply as needed.
  • Protective clothing – Long sleeves and pants can help prevent mosquito bites.
  • Draining standing water – The types of mosquitoes that can transmit West Nile virus tend to breed in urban areas, particularly in yards. Inspect your yard and make sure that there are no objects such as toys, garbage can lids, plant pots, or depressions in your yard that are holding water. Change birdbath water at least every four days. Make sure your gutters aren’t clogged and holding water.
  • Fans - Try using fans on your deck or patio to disrupt the cues that mosquitoes use to locate humans.
  • Mosquito Dunks – If you have an area with stagnant water that can’t be drained, trying using a larvicide called Bti. This is the same product that commercial mosquito control companies use to control mosquito larvae.

Visit to learn more about the city’s mosquito program, including weekly reports on mosquito activity, tips about how to reduce mosquito breeding sites on your property and protect yourself from bites and ways you can get involved as the city updates its program.

Published: July 27, 2018