"Replace insect attractant lamps once each year, in the spring!"

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This Rule of Thumb originated with my father, Don Gilbert. It was derived from the knowledge that lamps do, in fact, deteriorate over time (see graphs below)*, combined with customers observations that "our traps are not working as well as they did last year", and subsequent research. He got even more specific, saying that insect attractant lamps have an average, effective life of nine and one half months.

Recommending “spring” replacement simply insures traps are operating at their best during the summer insect season. This recommendation has been copied by most everyone in the industry and is routinely quoted as some sort of absolute truth. It's time tested to satisfy the vast majority of circumstances, but it is not an unquestionable fact.

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Perhaps, attractant lamps need to be replaced more often in a hospital with specific cross-contamination problems, in facilities where intravenous solutions are manufactured, or in climates with year-round insect problems?

Perhaps, they could be replaced less often in facilities where there are fewer flies to worry about or where fly control is relatively unimportant?

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If you're experimentally inclined, consider replacing half your lamps after one year. Then, compare how the new lamps perform relative to the older ones. Swap lamp positions, be as fair as possible, and let us know what you find.

I believe you will find, this (time tested) rule of thumb fits the vast majority of circumstances:

"Replace insect attractant lamps once each year in the spring!"

REFERENCES:

*  According to the manufacturer, the average output of our attractant lamp** (when matched with the proper ballast) will decrease from 100% to 80% in the first 100 hours (4 days), to 72% in 500 hours (20 days), to 68% in 1000 hours (41 days), and to 60% in 2000 hours (83 days).

The deterioration continues at a decreasing rate, approximately 3% a month. 15 watt lamps will deteriorate a little faster than 20 watt lamps and 20 watt lamps a little faster than 40 watt.