Updates In Using Black Lights

Many pest professionals often consider the use of black light lamps (often simply referred to as "black lights") as inspection tools primarily associated with the inspection of incoming food goods to warehouses to detect rodent contamination. This is unfortunate because black lights can offer pest professionals valuable insight over conventional rodent and wildlife inspections that use only a flashlight.

AN INSPECTION TOOL. Black lights can be used for the following:

1. To identify specific points where rodents are entering buildings around doors, utility openings, deteriorating walls, etc.

2. To detect elevated runways of roof rats along darkened ledges in hard-to-reach areas.

3. Pinpointing the high activity areas of rodents (as well as some urban wildlife) to aid in the most effective bait or trap placements. This insight can be particularly valuable inside challenging accounts such as supermarkets, apartment complexes, seed warehouses, restaurants and office complexes within old renovated buildings.

4. To help identify elusive rat activity areas. These rats often do not leave visible fecal pellets but do leave urine deposits.

5. As monitoring tools for proactive inspections for rodents and wildlife within ceiling, floor and utility voids inside sensitive accounts such as schools, hospitals, nursing homes and others such accounts.

6. To identify the extent of mouse urine deposits and contamination inside apartments and homes with individuals allergic to mouse infestations.

7. To identify possible rodent infested or contaminated incoming goods in food warehouses.

8. To demonstrate to various clients (food-serving establishments, schools, managers, etc.), the extent of current infestations, structural disrepairs needing their attention, harborage removal efforts and other areas and situations needing client involvement.

But despite their advantages, black lights are generally underutilized by pest management professionals because:

1. Quality black lights are relatively expensive, and thus, are not likely to be issued to every technician. But it is not necessary that every technician maintain a lamp on his or her service vehicle. Most companies that use black lights keep one lamp at the branch office to be taken out only when needed.

2. Inspectors must know how to correctly interpret fluorescing items to avoid chasing false positives.

3. To get the most benefit from exterior black lighting efforts, the inspection is best conducted during the evening hours. Still, the advantages gained by using black lights outweigh these minor drawbacks or inconveniences.

BLACK LIGHT LAMP MODELS. Purchasing a quality black light is important. Inexpensive lights will not provide consistent and/or reliable feedback. There are several manufacturers of black lights -- your local distributor is the first place to start when looking for one.

Two companies on the West Coast and the East Coast that offer black lights include the Ultra Violet Products Company of Upland, Calif. (800/452-6788; www.uvp.com) and the Spectronics Corporation in Westbury, N.Y. (800/274-8888; www.spectroline.com).

When selecting a quality black light lamp for field rodent and wildlife inspections two factors are critical: lamp strength and portability. Two types of black lights offer this:

• Battery-operated UV hand lamps offer portability. But be sure to purchase those models with adequate power (e.g., 730-800 uW/cm2 at 6 inches viewing). Lamps priced at about $175 to $225 provide this power range and good durability. Still, with portable units of this strength, the lamps need be held at about 6 to 8 inches to the surfaces being inspected to most accurately analyze the fluorescence patterns and colors.

• More powerful lamps (12 volt) are also available that come with the option of plugging into electrical receptacles or to shoulder strap battery packs. The combination of strength and portability is attractive considering the types of places and mobility needed when conducting animal pest inspections. The stronger lights also decrease the need to be constantly bending over to get close to the surface. These units are only slightly more expensive, but are worth it.

Even more powerful lamps are available for those operations requiring the power (e.g., warehousing operations), but these lamps must be plugged into building electrical lines for power (ranging from 100 to 240 volt outlets).

IDENTIFYING RODENT URINE. Here are some tips to help PCOs in the identification process.

1. When rodent urine is fresh it fluoresces bluish-white. Dry urine fluoresces yellow-white and becomes duller with age. Other than estimating "relatively fresh or old," it is difficult in the field to accurately determine the specific age of the urine.

2. Rodent urine is typically visible in a linear, trickling, droplet formation. As such, larger droplets lead down to smaller ones. In heavily contaminated or marked areas, urine stains may form large patches of urine surrounded by scattered smaller droplets of various sizes.

3. Large splash-like patterns exhibiting a radiating pattern away from the main patch or spot are not typical of rodent contamination. Human urine, or a spill of some type of fluorescent liquid material, is likely the cause of such patterns.

4. Rodent hairs fluoresce bluish-white and can be easily identified on boxes, runways or when ingrained in fabric sacking or intermixed with grains or other commodities.

Next month, we will discuss several specific tips for using black lights in the field as well as how to avoid false positives with the lamps (i.e., identifying a stain as rodent urine when it’s not).

Editor’s note: This is the first in a two-part series. The second part appears next month.

The author is president of RMC Pest Management Consulting, Richmond, Ind. He can be reached at 765/939-2829 or rcorrigan@pctonline.com.