Updates In Using Black Lights, Part II

Last month, I discussed how black light lamps can provide valuable inspection insight for rodents and some urban wildlife inspections and the importance of selecting quality lamps. This month, let’s take a look at some specific tips for using black lights in the field, as well as how to avoid making false positives with the lamps (i.e., identifying fluorescing stains as rodent or other animal urine when they’re not).

AVOIDING FALSE POSITIVES. When using black lights it is important to keep in mind that several commonly used cleaning and lubrication items — even some food materials — will also fluoresce under black lamps. Around commercial facilities, certain greases, lubrication oils and cleaning solutions will fluoresce when illuminated. Bleach, for example, fluoresces a bright bluish-white.

Because of this, some pest management professionals are hesitant to use black lights because they fear making a false positive and either unnecessarily alarming a client or wasting precious time inspecting for non-existent rodents. But with a little practice, noting the specific pattern of the splash and keeping in mind the particular situation as you inspect, false positives can be minimized. Moreover, quality black light lamp kits come with detailed descriptions of the different items that fluoresce, guides allowing you to distinguish between rodent and non-rodent stains. Of course, like learning to use any new piece of equipment, these guides and descriptions should be carefully reviewed prior to taking the lamps into the field.

THE REAL WORLD Here are some tips for using black lights in the field:

1. Associate the evidence with the location. To identify areas where rodents may be entering buildings, black lights can be used at night. Shine the black light over and around suspected building holes and gaps surrounding utility lines and the side bases of all doors (especially bay and garage doors and all other suspect areas). Fluorescing trickling trails in these and similar areas are good indications as to the possible presence of rodents. It is not likely that cleaning agents, oils, greases or fluorescent food items will be seen in these areas in trickling trail patterns.

Consider for instance, a utility line leading into and through a wall that was left unsealed. When black lighted, the line and opening area fluoresces trickles of yellow-white — a good indication of the likelihood of rodent entry.

2. Inspect the aerial areas. When inspecting for roof rats or other urban wildlife species gaining access to attics, the rafters within attics or exterior overhangs can be lighted. In these areas, the specific entry areas where aerial utility lines enter the building should be lighted to inspect for possible tree squirrels, roof rats, deer mice or other pests. Such locations are also not likely to contain many non-mammal materials in trickling patterns.

3. Direct the light specifically between tight spaces at corners and along ledges. Rodents prefer to travel such areas for protection they offer from predators.

4. Don’t stop the inspection just upon finding fluorescing trails. Areas and items which show fluorescent trails merely provide you with a clue that there may be rodents active in the area. Always look further for additional signs such as hair, fecal pellets or rodent damage. In other words, black light lamps should prompt you to look further and deeper. Without the use of the lamp, we sometimes have no initial clue indicating the need for a detailed inspection and incorrectly conclude there are no rodents when in fact there are.

5. Learn the patterns. In situations where there may be non-mammal fluorescing items, each item usually exhibits its own unique fluorescent color and pattern. When seen repeatedly, and by matching the patterns up with the guides as provided by the manufacturers, experienced inspectors can separate the various stains and patterns as rodent or non-rodent.

6. Shipping and receiving inspections must be done carefully. In food inspection and warehousing operations, inspectors and shipping/receiving personnel must be particularly astute to the correct use of black lights to avoid false positives and causing costly product rejections issues. Incoming goods should never be rejected on the results of black lighting alone. Additional rodent signs should be sought out. In questionable cases, the suspected contaminated items should be chemically analyzed by a qualified laboratory.

In the past, urine test kits (e.g., thymol blue reactionary tests for uric acid) were included or available with black lamp kits for on-site chemical analysis. But the shelf life of the reactionary chemicals used in these kits is short. Thus, such a chemical test kit is of little practical value to a pest professional who may need to conduct such tests infrequently. Besides, for pest professionals, such test kits are irrelevant. The objective of black lights inspections is not to verify rodent urine, but to assist in identifying possible pathways or activity areas of rodents, or to use the light as a specialized inspection and monitoring tool as discussed in last month’s column.

Few things are more interesting than having insight to situations and happenings which were previously hidden to us. If you’ve ever worn a pair of night vision goggles, or watched a farm pond get drained, you know the feeling. It is also the same excitement we get when we open a wrapped present. We can’t wait to see what is inside or what previous secret is about to be revealed to us.

For professional-level rodent and animal pest inspections, a black light lamp can provide you with this additional and exciting insight into the secretive world and travels of rats and mice. Supplementing your inspections with black light lamps also elevates your professionalism up a notch or two compared to your competitors. This can be very revealing — to your clients!

Editor’s note: This is the second in a two-part series. The first part appeared in January PCT and can be read below.

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).

 

 

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