Sterile mosquitoes vs bug zappers
The crackle sounds like progress. The studies say most of what's crackling isn't mosquitoes.
Bug zappers kill very few mosquitoes. In a Delaware study of 13,789 insects killed, only 31, or 0.22%, were biting flies, including mosquitoes, and almost half were harmless aquatic insects.¹ Sterile male mosquitoes reduce mosquitoes at the source: wild females that mate with them lay eggs that don't hatch, and other insects aren't affected.
1. Frick and Tallamy, University of Delaware, Entomological News 107(2):77-82, 1996, as summarized by Iowa State University Extension, https://yardandgarden.extension.iastate.edu/article/1996/6-14-1996/bugzapper.html.
How bug zappers work
Ultraviolet light draws insects in. An electrified grid kills them.
That works well for insects that fly toward light at night, such as moths and beetles.¹ Biting female mosquitoes mostly find people by the carbon dioxide we breathe out and by body odor, not by ultraviolet light. A University of Florida entomologist noted that mosquitoes can detect carbon dioxide at levels as low as 50 parts per million.²
The catch data is consistent across studies:
- Delaware, 1994 season. Of 13,789 insects killed at 6 suburban sites, 31 (0.22%) were biting flies. 6,670 (48.4%) were non-biting aquatic insects, and 1,868 (13.5%) were predators and parasites that help control pests.³
- Florida, one night. Of about 10,000 insects killed by one zapper at the UF/IFAS Florida Medical Entomology Laboratory, 8 were mosquitoes.²
- Indiana backyards. Female mosquitoes were 3.3% of an average night's 3,212 insects killed, and 11 days of continuous running did not reduce the mosquito biting rate in the yards.⁴
University extension guidance sums it up: studies show zappers "do not reduce the number of biting mosquitoes," and they kill other insects more often than mosquitoes.¹
1. Rutledge, C. R., "Mosquito Control Devices and Services for Florida Homeowners," ENY-692, University of Florida IFAS Extension, first published December 2003 (archival copy), https://journals.flvc.org/edis/article/view/109141. 2. University of Florida IFAS news release, July 23, 1997, quoting entomologist Jonathan Day, https://archive.news.ufl.edu/articles/1997/07/snap-crackle-pop-electric-bug-zappers-are-useless-for-controlling-mosquitoes.html. 3. Frick and Tallamy, Entomological News 107(2):77-82, 1996, via Iowa State University Extension, https://yardandgarden.extension.iastate.edu/article/1996/6-14-1996/bugzapper.html, and University of Delaware, https://www1.udel.edu/PR/Messenger/96/3/6.html. 4. Nasci, Harris and Porter, Mosquito News 43(2):180-184, 1983, South Bend, Indiana: "Failure of an insect electrocuting device to reduce mosquito biting."
How sterile males work
The opposite of a zapper: built for one target, and every other insect is left alone.
Sterile males are biological control that's precisely targeted: it affects only the two mosquito species we release. A zapper waits for insects to fly to its light; our males go looking for wild females, including where sprays and traps can't reach. Moths, beetles, bees, people and pets carry on as before.
Four steps to fewer mosquitoes
Side by side
A zapper and a season of sterile males, on the questions that matter in a yard.
| Compared on | Sterile males (SMF) | Bug zappers |
|---|---|---|
| What it does | Stops wild females from producing offspring and collapses the population | Kills insects drawn to its ultraviolet light |
| Coverage area | The property in your program | Insects that fly to the light; biting not reduced in backyard tests¹ |
| Reaches hidden breeding sites | Often. Males find wild females on their own, including in gutters, drains, dense plants and the yard next door | No. It reaches only insects that fly to the light |
| How long it lasts | Builds over the season while releases continue | Only while it's switched on |
| Effect on other insects | None. Only the two mosquito species we release. | Mostly non-target insects; 0.22% biting flies in one study² |
| Pets and kids | Nothing applied; males don't bite | No chemicals; an electrified grid behind a guard |
| Maintenance | A release plate twice a month (once a month in winter), about a minute; on commercial sites, our team or your staff release | Cleaning the grid and tray, replacing bulbs |
| Cost model | Quoted for your property | One-time device purchase, plus electricity and bulbs |
| Best for | Season-long reduction of daytime and dusk biters in yards | Light-attracted insects such as moths near a building at night |
1. Nasci et al., Mosquito News, 1983; University of Florida IFAS Extension, ENY-692. 2. Frick and Tallamy, Entomological News, 1996.
Why the bycatch matters
A zapper's victims are often your yard's free pest control.
The Delaware team found that more than 1 in 8 insects killed were predators and parasites, such as ground beetles and parasitic wasps, that eat or attack other pests.¹ Almost half were non-biting aquatic insects from nearby streams, which are food for fish and birds.² Taking them out doesn't touch the mosquitoes breeding in your gutters and plant saucers.
A California public district, the San Gabriel Valley Mosquito and Vector Control District, advises residents that zappers mainly kill beneficial insects, and recommends removing standing water and using repellent instead.³
1. Frick and Tallamy, 1996, via Iowa State University Extension, https://yardandgarden.extension.iastate.edu/article/1996/6-14-1996/bugzapper.html. 2. University of Delaware, The Messenger, Vol. 5, No. 3, 1996, https://www1.udel.edu/PR/Messenger/96/3/6.html. 3. San Gabriel Valley MVCD, California, August 1, 2019, https://sgvmosquito.specialdistrict.org/2019-08-01-are-bug-zappers-really-effective-against-mosquitoes-the-answer-may-surprise-you.
When a bug zapper is the right choice
If your problem is moths and beetles around a light, a zapper does that job.
Zappers do kill large numbers of night-flying insects that come to light. Near a barn door, loading dock or porch where light-attracted insects are the nuisance, that can be what you want. Mount it away from where people sit, since it pulls insects toward itself.
For mosquitoes, the evidence points elsewhere. If you already own a zapper, consider switching it off during mosquito season to spare the beneficial insects.
Using them together
There isn't much a zapper adds to a mosquito program. Here's what does.
- Sterile males all season for the Asian tiger and yellow fever mosquitoes, the ones that bite in yards by day and at dusk.
- Tip out standing water after rain: buckets, saucers, toys, clogged gutters.
- Skin repellent on evenings when night-biting mosquitoes are out. See Sterile mosquitoes vs repellents.
- A fan on the patio for dinner outside.
For lure traps and egg traps, see Sterile mosquitoes vs mosquito traps and Sterile mosquitoes vs CO2 mosquito traps.
FAQ
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1. University of Florida IFAS news release, July 23, 1997. 2. Frick and Tallamy, Entomological News, 1996, via Iowa State University Extension. 3. San Gabriel Valley MVCD, 2019.
Do bug zappers kill mosquitoes?
A few. Mosquitoes were 8 of about 10,000 insects in a one-night Florida test, and biting flies were 0.22% of the catch in a Delaware study.¹ ²
Do bug zappers attract mosquitoes?
Not much by light. Female mosquitoes follow carbon dioxide and body odor. A University of Florida entomologist warned that zappers can still draw more mosquitoes into a yard, where they find people instead.¹
Are bug zappers bad for the environment?
They kill large numbers of non-target insects. In the Delaware study, almost half were harmless aquatic insects and 13.5% were predators and parasites of other pests.²
Do bug zappers work for flies or gnats?
In the Delaware study, biting flies and gnats were a tiny share of the catch.² Zappers mostly catch insects drawn to ultraviolet light at night.
What works better than a bug zapper for mosquitoes?
Removing standing water and wearing an EPA-registered repellent, as public districts advise.³ To reduce the mosquitoes breeding on your property over a season, a sterile male program targets the species that bite in yards.
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