Are Black light bug zappers effective in killing mosquitoes?
February 18, 2019
In my blog post Zappem’ Dead – Camp Savvy’s answer to mosquitoes, I stated that mosquitoes are not attracted to UV light. This statement was based on a frequently cited study, Frick, T. B. and D. W. Tallamy. 1996. Density and diversity of nontarget insects killed by suburban electric insect traps. Entomological News. 107(2): 77-82. This study found that blacklight traps do a poor job of attracting biting flies like adult female mosquitoes and biting gnats, and, in fact, attracted and killed many more beneficial insect species. The traps were therefore considered to be environmentally harmful because of damage to the natural fauna. Their survey of insects electrocuted during routine use of electric insect traps revealed only 31 biting flies, a minute proportion (0.22%) of the 13,789 total insects counted.
What prompted me to do further research was that I am busy preparing a video of a black light device similar to a “bug zapper” than can be used with 12V batteries. I noticed that on the box it displays in big, bold letters “Black Light”. So I thought: “what is the difference between UV lightsand black lights?”
As with visible light that has different frequencies of light (red, yellow, blue, etc), UV light also has different frequencies typically divided into UV-A, UV-B and UV-C light.
Sunlight is the biggest source of UV. UV-A rays are the longest-wavelength, lowest-energy kind of UV radiation and the kind that is least harmful. It is the UV-B and UV-C rays in sunlight that causes the most damage.
Strictly speaking a black light is a UV light with a special phosphorescent coating that emits UV light, specifically UV-A light. It is typically used in bug zappers.
Do they attract mosquitoes?
Now this is where it becomes a bit fuzzy. According to Frick & Dallamy’s research, not really. To me this makes perfect sense and is in line with what I would expect. Many flying insects are attracted to UV light for the simple reason that most flowers reflect UV light in the same way that they reflect visible light. The only difference is that we cannot see the UV light. Insect of course can. Below is an example of what humans see vs what insects that can see in the UV spectrum, can see. It stands to reason therefore that insects such as butterflies, bees and moths would be attracted to black lights.
Mosquitoes however do not care about finding nectar. They find their food source by following our Carbon-Dioxide trail and our body heat. They are also sensitive to the sweat from our skin. For this reason I would expect mosquitoes not to be attracted to black lights to the same extent as nectar eating insect. This is corroborated by the research cited above.
I’ve also found contradicting research that sing the praises of the effectiveness of black light traps.
Hee Il Lee, Bo Youl SEO, E-Hyun Shin, Douglas A Burkett, Jong-Koo Lee and Young Hack Shin. 2009. Efficiency Evaluation of Nozawa-Style Black Light Trap for Control of Anopheline Mosquitoes found that each black light trap in livestock enclosures killed 7,586 female mosquitoes per trap per night during the peak mosquito season (July-August) in Korea. They conclused that black light traps were an effective means of reducing mosquito numbers.
Another study by Chun-Xiao Li, Michael L. Smith, Ali Fulcher, Phillip E. Kaufman, Tong-Yan Zhao and Rui-De Xue, 2015. Field Evaluation of Three New Mosquito Light Traps Against Two Standard Light Traps to Collect Mosquitoes (Diptera: Culicidae) and Non-Target Insects in Northeast Florida
found that “in the evaluation of light traps without a chemical lure, the black light and CDC light traps collected large numbers of mosquitoes, and the ratios of mosquitoes to non-target insects were 1:7.5 and 1:8.9, respectively.”
According to research done by the University Of Florida, Institute Of Food & Agricultural Sciences. “Snap! Crackle! Pop! Electric bug zappers are useless for controlling mosquitoes, says pest expert.” ScienceDaily. ScienceDaily, 30 July 1997, “They <bug zappers> are a total waste of money. Bug zappers will not control mosquitoes or other biting insects such as horseflies, dogflies or deerflies,”
According to this article “Scientists at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach, Florida, also examined the effectiveness of bug zappers in 1997. A single bug zapper in their study killed 10,000 insects in one night, but just eight of the dead bugs were mosquitoes.” They also say that “University of Notre Dame researchers conducted a similar study in 1982, with similar results. In an average night, a single bug zapper in South Bend, Indiana, killed 3,212 insects, but only 3.3 percent of the dead insects were female mosquitoes. In addition, these researchers found that the UV light seemed to draw more mosquitoes to the area, leading to more mosquito bites.”
I am now totally confused and honestly do not know what to believe. Are black light bug zappers an effective control against mosquitoes or not? I guess the only way to know is to devise my own research project and then, based on the results, to make up my own mind.
Watch this space….