Do CO2-based mosquito traps work?

Question

My parents get a lot of mosquitoes in their garden during the summer. We've tried torches with citronella additives in the oil, but this has not been effective.

I don't want to install a UV-based insect killer, as I don't want to kill non-biting insects.

I've seen some devices that purport to attract the mosquitoes via CO₂ (which should only attract biting insects). However, these seem to be very expensive with substantial upkeep costs.

How well do these devices work when compared to other area methods such as citronella, area sprays, etc?

Answer 1

CO₂ traps, according to the NIH, fare better than most other types of mosquito traps. For best results, you want to use a trap with counterflow technology (CFG). Note that you have to keep your "scent" down or it will overwhelm the CO₂.

Traps baited only with light or octenol caught few mosquitoes, whereas many were caught by traps baited with CO2 alone or in combination with either of the other candidate attractants. CO2 baited traps, with or without light, caught the most Aedes. The combination of CO2 and octenol attracted most Cx pipiens, but this apparent synergy was not significant. Using a caged hamster compared to CO2 as bait in a CDC light-trap with only intermittent fan suction, the hamster attracted less mosquitoes than CO2 emitted at a rate of 225 g/h on days 1 and 2, whereas on days 3 and 4 the smell from the hamster's cage became significantly more attractive than this rate of CO2 for all species of mosquitoes.

USDA tested a few traps, and the CO₂ Trap with CFG scored the best (page "50", but really the fourth page, top chart). The Mosquito Magnet-X by American Biophysics Corp is a counterflow geometry updraft trap using CO₂. It weights 2.7kg (5.95lbs). Unfortunately it does cost several hundred dollars (US) and requires an external propane tank. Unless you are car camping, I would not consider it practical.