Insect light traps (ILTs), also called insect electrocutors or bug zappers, can be very effective in attracting, trapping, and zapping flying insects. But it is important to realize that attracting is exactly what the insect light trap is doing: It's drawing in the insects in order to trap or zap them. If you put a trap right on the patio or porch where you are sitting, you are actually going to bring more mosquitoes, flies, and moths to you! Therefore, a light trap must be correctly placed so that it is not attracting mosquitoes or flies toward people or into a building.
Types of Insect Light Traps
The basic parts of any ILT include a light to attract the insects, a receptacle or glue board to contain the live, dead, or dying insects, a housing to hold it all together, and, in some cases, a bait:
- Light: An ultraviolet (UV) light, which is attractive to most flying insects.
- Trap: Some ILTs literally zap, or electrocute, the incoming insects. In these cases, there is often a raised-edged pan at that bottom of the ILT to hold the dead and dying insects. In other cases, the insects are not zapped but instead are caught on a glue board or glue strip when they arrive in the lighted area.
- Housing: Housing come in a variety of sizes and styles, but most are configured with light within a protective cage or grill.
- Bait: In non-electrocuting, glue board-based ILTs, the glue board often includes an attractant that helps to lure insects to the glue once they are inside the trap.
Proper placement of ILTs is critical so that invading insects are being attracted to the light, rather than the light attracting more insects.
- Outside: Place traps away from the areas in which people will be congregating. For example, if you're planning a cookout on your patio, place the ILT in the yard some distance away. This will draw insects away from the people to the distant light. If the light is placed on the patio, it can compel insects from across the yard to fly over and join the party.
- Indoors: Place ILTs so they are out of view through glass doors and windows (when looking in from outside) but close enough to quickly attract any insects that get indoors. If flying insects can see the light from outside they can be drawn to and through an open door or unscreened window.
- Near food areas: Position ILTs so that dead insects cannot fall onto food, food-contact surfaces, or utensils. The U.S. Food and Drug Administration (FDA) recommends that ILTs be placed at least 5 feet away from any exposed food or food-contact surface.
- Height: There are varying opinions about the best height for placement of ILTs, but this primarily depends on the insect being targeted. Insect flight patterns near lights vary, as do the heights at which different insects fly. While recommendations may differ by source, there are a few general rules of thumb you can follow:
- Large flies, such as houseflies, fly low, so outdoor traps should be placed about 3 to 4 feet above the ground. Indoors, it can be just as effective to position traps at higher levels.
- Small flies, such as fruit flies, are best caught at levels of about 4 to five feet from the floor.
- For most mosquito species, hang traps 5 to 6 feet above the ground.
Whether insects are trapped on a glue board or they're zapped and fall into a tray, an ILT should be cleaned out regularly. If the trap is indoors, it should be cleaned on a weekly basis. If dead insects are allowed to build up, they can attract secondary, scavenger insects and begin a new infestation.
With glue board or glue strip traps, the board or strip should be changed regularly, as needed, both to remove dead insects and to maintain efficacy, as dust can gather on the glue and decrease the adhesion.
Insect light traps, when placed and used correctly, can be a very effective form of control of occasionally invading mosquitoes, houseflies, small flies, and moths. However, the traps cannot be expected to control a serious infestation if conditions exist for the insect to be living and breeding in or around the home, and/or entering the home.
In such cases, effectiveness will be dependent on finding and eliminating the source of the problem, such as standing water or unsanitary areas. It also helps to repair entry points, such as torn screens, unfitted doors or windows, or cracks and gaps in exterior walls or foundations.