It’s a well-known fact that light attracts pests, and yet, most facility managers don’t consider pest management when designing and installing lighting systems in and around their properties.

Many nocturnal flying insects are drawn to exterior lighting around buildings — pests such as moths, flies and beetles. Why? There is no definitive answer, but one theory is that they evolved to use the natural light of the sun or moon to navigate. Keeping this natural light on one side of their body helps maintain a straight, steady flight path. When they come across artificial light, they mistake it for the sun or moon and try to use it as navigational aid, but because it emits light in multiple directions, they become confused. Now, keeping light on one side of their body leads them to fly endlessly around the light source.

When lighting attracts insects to a building, there’s a greater chance they will find a way inside through unscreened windows, doors, cracks and crevices. What’s more, insects can attract other pests to a property: insect predators including rodents, birds, bats and raccoons.

The good news is that proper lighting systems at strategic locations can be used to minimize pest problems. Here are some tips to keep lights from creating more pest pressure on a property.

Types of lights

Unlike humans, most insects can see ultraviolet light (UVL) and they’re attracted to it. In fact, a light’s UV output is one of the most significant factors in how attractive it is to an insect and is the basis for insect light traps. Any lights around a property that emit UVL, including both florescent lights and mercury vapour lights, will attract insects.

The colour of the light also plays a role in its attractiveness to insects. The bright white and bluish light produced by mercury vapour lights and white incandescent or florescent lights is most attractive to insects. Yellow, pink and orange light, produced by sodium vapour and halogen lights, is least attractive. Red bulbs are even less attractive, but they aren’t ideal light producers for human visibility.

A third feature to keep in mind is the construction of the light fixture. Lights produce warmth, to which insects are also attracted. So if a light fixture is not dust- or insect-tight, it may become a harbouring point for insects in general. Fluorescent light fixtures are often to blame for harbouring pests.

Tips for selecting products

• Use sodium vapour lights and other low ultraviolet-light (UVL) producing lights whenever possible, especially in high risk areas such as entrances. Sodium vapour lights produce no UVL and, as a result, attract fewer insects.
• Choose yellowish and orange-tinted lights, as they are less likely to attract pests.
• If possible, avoid bright flooding lights; they tend to attract insects from near and afar.
• Ensure light fixtures are dust- or insect-tight.
• Shield outdoor lighting so high-flying insects cannot see it from above.

Positioning fixtures

The placement of lights around a property also plays a factor in attracting pests. Avoid mounting lights near door entrances, so as not to allow pests easy access to the building. Instead of mounting lights on the building, move them to poles placed away from the building and direct the light toward the entrance. Position exterior lights at least five metres away from entrances.

As with entrances, also avoid mounting exterior lights near air inputs, ventilation systems and roof opening/hatches, even if they are screened. Turn off any roof lighting unless maintenance is being performed after dark.

Ground lighting can also be troublesome, attracting not only flying insects, but rodents. Drawn to the warmth emitted from lights, rodents may burrow near the lights to stay as close as possible to the heat.  To avoid burrowing rodents, surround ground lights with six millimetres of pebble rock and use high-pressure sodium lights.

Mercury vapour lights are highly attractive to pests, which means locating them anywhere on or near a building is a bad idea; however, they can also be used to keep pests at a distance. Consider placing mercury vapour lights on columns about nine metres away from entrances to draw insects away. Also consider creating a perimeter of distractive light around the building by placing mercury vapour lights away from the building, leaving about 30 metres in between each light.

While exterior lighting can be a major attractant for pests, light placement and the type of bulbs used can greatly reduce the number of insects that are attracted to a building.

Alice Sinia, Ph.D., is the resident entomologist – regulatory/lab services for Orkin Canada focusing on government regulations pertaining to the pest control industry. With more than 10 years of experience, she manages the Quality Assurance Laboratory for Orkin Canada and performs analytical entomology as well as provides technical support in pest/insect identification to branch offices and clients. For more information, email Alice Sinia at asinia@orkincanada.com.