Proper Use and Maintenance of Insect Light Traps

If maintained and used properly, insect light traps (ILTs) can be very effective at both capturing and monitoring for flies. ILTs allow for easy identification, because generally, intact flies are preserved in the sticky traps. The following maintenance and use tips will help ensure your ILTs are working to the best of their ability:

Light Trap Location. Location and proper positioning are main factors in successful light trap usage:

Install lights on the same wall as entryways, if
possible (Photo: Mike Waldvogel, NCSU

• Install traps either on the same wall as the entryway (see photo at left), or on a nearby perpendicular wall. The attractant light should not be seen from the outside to avoid attracting outdoor flies.
• Avoid other light sources that could potentially compete with the trap. Try to avoid placing ILTs in brightly lit areas, if possible.
• Insects need to be able to see the light, so make sure that there is nothing placed in front of the ILT that would substantially block the light.
• For day-flying insects like house flies, install wall-mount or corner-mount light traps low.
• Ceiling-hung traps work better for night fliers like stored product moths.
• Install ILTs along the path to stored or processed food. Narrow hallways are good installation sites. ILTs are most effective where flying insects are funneled into narrow spaces.
• In food-processing areas, place ILTs so as to draw insects away from the food. Do not install ILTs over exposed food or near food prep surfaces. 
• Place open tube electrocuting traps near back doors that lead to garbage areas and dumpsters but are not near food or customers.
• To capture Drosophila (fruit flies), place an ILT that contains a sticky board low behind counters or behind beverage or salad bars. 
• Place ILTs in drop ceilings or attics to trap overwintering flies, such as cluster flies. 
• Don’t place ILTs near air blowers or in areas where there are strong air currents. 

Trap Maintenance. Be sure to dust off the lamps and the guard door on a regular basis. Use a wire brush to remove insects from the grid. The lamps, reflector and grid should be periodically washed with warm, soapy water. Inspect the trap for signs of electrical problems like damaged wires, cracked insulators, scorched transformers or loose electrical connections. Most ILTs will automatically turn off the electricity when the trap is opened for inspection or maintenance. However, it may be necessary to unplug the unit before cleaning.

Collection trays should be emptied and cleaned regularly. Dead insects left in the collection tray may attract dermestid beetles, so don’t wait until it’s full of insects to empty the tray. A small paint brush can be used to brush insect parts out of the catch tray and other parts of the trap.

Many ILTs use glue boards rather than a collection tray. Glue boards that are dusty or full of debris and insects will not be ineffective and should be changed. Even if the glue boards are clean and empty, they can dry out over time. Check the manufacturer’s recommendations for replacement of the glue board.

Most manufacturers recommend that lamps be replaced at least annually. The effective life of a lamp is about 7,000 hours or 9½ months of use. Even if the light appears alright, it may no longer attract insects. It’s good practice to replace the lamp in the spring to ensure they are most effective during peak season.

Examine the catch. Examine traps regularly. An increase in trap catch or the appearance of a new pest may indicate a developing pest problem somewhere in the building.

Use and promote IPM. Fly management will get an extra boost if other pest control strategies, such as exclusion and sanitation, are integrated with ILTs. Discuss with and educate your customers about the issues that may be contributing to a fly problem. Provide recommendations for minimizing these conditions. In addition, take advantage of any opportunities for some up-selling. For example, you might recommend the use of fly fans (air curtains) and/or vinyl strips at exterior doors and loading docks.