Last year I asked the lighting community if there were any topics of interest that I might write about. I was happy to receive a question from Steve Schafer of Milow Electric in Long Lake, Minnesota. He asked me to investigate the effects of LED light on flying insects.
Most everyone has enjoyed family meals outdoors on the patio — or tried to — only to find that during the summer months, flying insects can make such gatherings unbearable. Halogen, incandescent and fluorescent light sources all have the potential to attract flying insects due to their wavelengths and the heat generated by the lamps.
With the rise in West Nile virus cases, people are more careful about selecting light sources. For several years there has been discussion as to which new LED light sources reduce the attraction of insects to them. In studies related to this subject, it’s been determined that proper thermal management along with choosing LED light sources with the right wavelengths successfully reduces insect interest.
Insects process light differently than humans. But like us, they seem to have a particular “taste” for the lights that attract them. Insects use ultraviolet light to guide themselves at night, thus making the back-porch bug zapper a popular summertime accessory for us humans.
Some scientists in Pakistan discovered that insects are more attracted to one particular color spectrum. The purpose of this study was to help create light-driven insect traps as an alternative to pesticides for the agricultural industry. The results found that 22 percent of insects were attracted to blue light.
So, how can these findings help us design a less bug-friendly lighting system? We now know that the warmer the wavelength, the fewer insects will be attracted to it. When designing a lighting system for an area in which people will congregate, it will be necessary to select light sources that lean more toward the red spectrum.
Using bulbs with a Kelvin temperature of 2,200 K in these areas can create a warm, relaxing atmosphere with a reduced number of insects flying around. Bistro light strings equipped with 2,200 K bulbs can provide this effect, as well as a broader span of lighting. In some commercial applications I’ve seen red and 2,200 K bulbs mixed together in these strings.
Lighting with these color tones also helps relax our eyes from the blue spectrum of light we view all day on our computers and phones. In other areas of a property, away from where people group, other color temperatures can be used. You can still light up the big trees in the yard and create depth with back lighting. Task lighting that’s 5,700 K or brighter should always be put on some type of switch if located close to patios or gathering areas.
For outdoor rooms, you may need to use bulbs with two different Kelvin temperatures, warmer for dining and cooler for cleanup. Both lighting arrays should be on separate switches. Some manufacturers have made switching easier via color-changing products and smart home systems.
When selecting light sources for outdoor environments, be sure to read the specifications carefully, and select ones that produce no UV light. This will reduce the number of insects they attract and will also help avoid color shift in the phosphors applied to the diodes. Unknowing customers who buy lamps online may find themselves with an ultraviolet diode that is covered with phosphor to look like white light. UV will break down the phosphor and create a purple hue which will attract insects.
In my research, I have not discovered any truly bug-free light sources. Until they exist, it’s up to us as contractors and designers to do the best we can to reduce how attractive our installations are to those annoying flying insects.
I wish to thank Steve Schafer for asking me to research this subject. If you have a lighting topic you would like me to investigate, please email me. In the meantime, keep your customers buzzing about your great designs … and not the bugs!
Kevin Smith is the national technical support and trainer at Brilliance LED LLC, Carefree, Arizona, and can be reached at email@example.com.