Questions & Answers

Q: We’re using more insect light traps as part of our IPM program and we’ve heard many recommendations on when to change the light bulbs. Some manufacturers claim a bulb should be changed after one year while others seem less certain. What is your recommendation?

A: I believe it’s important to understand that the ultraviolet light output of all lamps or bulbs decreases over time. While a lamp may appear to be effective due to its brightness, it may have grown less capable of emitting ultraviolet light. I should further point out that the rates of decay are probably not constant or consistent as they will vary with bulb manufacturer and the type of light trap in which they are placed.

Another point to remember is that flying insects typically trapped in these types of traps are attracted to the trap by ultraviolet light. Humans cannot see ultraviolet light. Therefore, you can’t judge the effectiveness or efficiency of a light bulb based on the brightness of the blue color since the blue light is not ultraviolet light.

In keeping with the concept of IPM, I believe that your light traps should be at their maximum efficiency when they are most likely to do well. The potential for flying insects in a particular account is probably not constant year-round. For example, it may be more intense in the late summer or some other time of the year depending on the part of the country and the type of environment in which your account resides. So, instead of replacing bulbs on January 1 each year, for example, you may want to schedule the bulb replacement just prior to the season when flying insects are their worst. This will require record keeping and being attuned to the natural fluctuations in pest populations.

An even better idea would be to obtain a UV light meter capable of measuring UV light output of your light traps at varying distances from the trap. This testing of the light traps on a monthly or quarterly basis should be a component of your IPM plan. I am aware of one manufacturer of these UV light meters that I believe are available in this country. The company which makes the meter is Advanced Systems, Ltd., out of England. Their web site address is www.advanced-sys.co.uk. You can also check with your distributor.

Jeffrey Tucker is president of Entomology Associates, Houston. Questions can be sent to Questions & Answers, c/o Entomology Associates, P.O. Box 70375, Houston TX 77270, or faxed to 713/681-9069.