Deadliest Catch

Brandenburg NA recently conducted field research with the assistance of McCall Services to understand the catch effects of blacklight (BL) and blacklight blue (BLB) bulbs for different types of flying insects.

THE OBJECTIVE. The objective of the research was to determine if using an insect light trap fitted with a mixture of regular “blacklight” (BL) and Woods glass-coated “blacklight blue” bulbs (BLB) catches more nocturnal flying insects when the trap is visible from the building exterior — as is commonly believed in the U.S. pest control industry. Although not normally considered structural pests, the insects may enter structures through loading bay doors and other entrances used at night, and are a potential contaminant for food manufacturers and food service providers.

The study aimed to concurrently capture night-flying insects using three identical two-tube insect light traps, each fitted with a different mix of bulb types: one with two regular uncoated BL bulbs; one with one regular uncoated BL bulb and one coated BLB bulb; and one with two coated BLB bulbs. A comparison of the number and insect type distribution would be used qualify the use of mixed bulbs for this purpose.

THE PROCEDURE. Three new insect light traps (standard model Brandenburg Genus Fli) were installed with six feet of separation in a covered outdoor storage location, which had three sheet metal walls and a chain link fence on the fourth. It was expected that the exposure to full sunlight would seriously reduce the potential for these traps to attract daytime-flying insects, which were not a consideration of the research.

ILT INSTALLATION. Each trap was fitted with two 15-watt Brandenburg Electrosect bulbs, either standard BL, Woods glass-coated BLB or a mixture of the two (as described previously). Each trap was fitted with a white standard Brandenburg Universal glueboard, and turned on for approximately 24 hours. At the end of the exposure period, the glueboards were collected and analyzed for capture count and insect type distribution.

The exposure was replicated nine times, with the bulb distribution rotated between the different light traps to eliminate positional influence (a total of three exposures for each bulb combination at each trap location). The trial ran from August through September 2015 and was located in northern Florida, and the statistical analysis was performed by I2LResearch, an independent certified and GEP registered research facility.

RESULTS. The volume of insects captured over the 24-hour period averaged 760 per glueboard (about 30 per hour over the 24-hour exposure period), with a high count of 1,696 and a low count of 276. The captured insects were sorted by orders, with a total of seven insect orders represented. (See Table 1.) The distribution of insect orders by bulb type was analyzed statistically; no statistical difference was found.

The total insect capture by bulb type was also analyzed statistically and, despite the numbers seeming to show a slight preference for the mixed bulb type configuration, no real statistical difference was found. (See Table 2.)

CONCLUSIONS. The colors of light that are actually produced by these bulbs is identical, with the coating on the BLB bulbs simply removing some of the visible portion of the light that is released. This has been shown to make no difference in the capture rate of common houseflies (Musca domestica), which seem to find the visible part of the light output uninteresting. Tests with other species of filth flies, such green and blue bottle flies (Calliphora and Lucilia species), have shown some statistical preferences for attraction to the BL bulbs over the BLB bulbs (Brandenburg unpublished), so it is possible that there may be some flying insects that find the BLB bulbs more attractive than the BL bulbs. However, at least in the vicinity where the test was performed, the results suggest that there is no capture advantage in use of either bulb, on their own or in combination, for nocturnal flying insects.

The author is marketing executive for Brandenburg NA. He can be reached at TahirRashid@b-one.com.

Author’s note: Brandenburg would like to thank the staff of McCall Services, specifically John Cooksey, who implemented the trial and provided data gathering and captured insect counts.