Fly Traps: Seeing The Light

Flying insect control is performed much differently today than it was years ago, and I am not only referring to the common house fly, blow fly or fruit fly.

Many industry professionals have spent time discussing the topic of fly control. Books such as Stoy Hedges’ Field Guide for the Management of Structure-Infesting Flies have paved the way for an ever-increasing discussion about these control programs. In addition, the increasing number of IPM programs that do not allow the fogging or ULV/ULD treatments of the past have required PCOs to change their approaches to flying insect control. And one such change has been to use fly light traps, not only for control, but for monitoring. Some fly light manufacturers have even begun referring to their products as monitoring devices. But there is more to this phase of pest control than installing light, jar or bag traps on walls, or hanging them in doorways.

Most fly light traps are designed to be easy to maintain and clean. Most manufacturers recommend changing the lights in the traps at least once a year, and many traps also employ shatterproof tubes, so they can be used in food preparation areas. Photo courtesy of Pest West.

WHY USE TRAPS? The purpose of using light traps is to monitor the populations of a particular flying insect. These traps also can offer expanded capabilities over jar traps. As with all pest control measures, the selection of a particular trap depends on the specific situation present.

The electric fly killers (EFKs, or light traps with electric grids) and their related glueboard products (let’s call them passive light traps, or PLTs) have a definite place in the market. These traps are being used extensively in food manufacturing facilities and restaurants, and have been showing up in many kitchens, fast food facilities and grocery stores. They also can be found in health care facilities.

The less obvious sticky lures, bag and jar traps are typically being used by PCOs in the monitoring/inspection processes where the cost of the larger, more expensive EFKs and PLTs would be prohibitive.

Light traps are designed to offer ongoing monitoring of flying insect populations, and also to provide some level of control. Many types of insects can be attracted to light traps, and a survey of a light trap’s catch tray or glue-board can tell you a lot about what is happening in that facility.

As mentioned previously, there are many species of flying insects that can be trapped. We can use attractants (usually food sources such as vinegar, banana, apples, etc.), pheromones (which attract certain species of flies or stored product pests), and light to draw the insects to the trap. When light is used as the attractant, the wavelength of the light is important. The wavelengths emitted attract a wide variety of flying insects, which can be both good and bad.

The blue- or green-lighted traps emit ultraviolet (UV) light. Often referred to as “black light,” its wavelength is typically between 300 and 400 nanometers. The green lights emit a green wavelength that is especially attractive to house flies.

Currently, there is a wide variety of flying insect light traps on the market, including both EFKs and PLTs. All of the traps on the market will attract and kill or trap flying insects, but the various types of traps available are suited for different situations and applications.

For instance, placing a large EFK on a loading dock and letting it run 24 hours will catch many types of insects, most of which are not in the facility and some of which you do not want to attract to the facility. Wasps and yellow jackets, as well as stored product beetles and moths, are among the insects that will be attracted to the area with this type of trap.

However, if the same EFK is used inside the facility correctly, it can head off flying insect problems or at least indicate if a problem exists. You will then need to decide how the insects got into the facility and what remedies you might take to eliminate the problem.

WHERE TO USE LIGHT TRAPS. Light traps can generally be used just about anywhere, but a few variables do apply to each situation: the customer’s attitude, the cost of the trap(s), and the time the pest control professional has available to do the job.

The customer’s attitude is important with regard to his or her expectations about how the traps will be used. The traps should not be viewed as control mechanisms, because they probably will not eliminate all of the flying insects in the facility.

Sanitation is also very important in the control effort. Once the device is used to identify the problem and point it out to the customer, the traps then become a valuable monitoring device. If you know there is a specific fly or insect involved and can use a jar trap for that insect, there is less money involved. However, the placing of any traps, especially light traps, means maintaining and monitoring them. This becomes more expensive for the customer and the PCO.

Some pest control operators lease or sell EFKs and PLTs to customers and leave it at that. While this practice may help cinch the deal, it is usually not a good idea. It does not save you time in monitoring, and it certainly doesn’t save the headaches if these machines are not maintained by the customer.

In FDA and USDA facilities there are some general guidelines as to where light traps can be used. In general, these regulations have been designed to prevent contamination of food with insects or insect parts.

Most of the traps on the market today are built with these guidelines in mind. And the “exploding fly” controversy has lessened because of the introduction of the PLT and the redesign of the catch areas of the traps and the electrical grids themselves. Also, only certain fly species were prone to “exploding.”

The size of the trap can make a difference in its attractiveness, and should be considered when monitoring traps. Certainly the intensity of the light being emitted will have some effect on the trap’s attractiveness. As the light UV output decreases, it is less attractive to the insects. Therefore, a lower catch may not mean better control.

There are two ways of testing the intensity of the light. One way is to replace the bulbs with new ones at regular intervals, and keep records of these changes. In fact, many companies place such records right on the trap like rodent station service tags.

Another tool that was introduced late last year is the UV-A Meter by Advanced Systems Ltd. (available through B&W Sales and Marketing, 800/843-6334). This meter will measure the ultraviolet output of the bulbs and tell you when their output is decreasing. Furthermore, the meter actually reads the difference between the ambient UV in the area and the UV output of the light. So when the output from the light drops off, the ambient UV light may be enough to “confuse” the insect, making the trap less attractive.

Using this feature, a PCO can determine placement possibilities and/or what wattage of light would be most effective. You can also use this device to monitor those lights you did not install, possibly to show the customer that their existing control or monitoring program needs some assistance.

An example of a floor plan layout of insect light traps in a production facility.

LOCATION, LOCATION, LOCATION. The credo of the real estate industry should be written at the top of your trap inspection sheet! Where light traps are placed is arguably the most important aspect of their use. Many times the placement will depend on the actual conditions you are working under. In large manufacturing plants and food manufacturing facilities, placing large units high, hung from the ceiling, is ideal for monitoring purposes. In other situations, where you are trying to head off the introduction of these pests, placing them low along walls protected from damage, will intercept invading insects.

Light traps vary considerably in appearance these days. Wall valances have become an interesting addition to the styles of traps available, and certainly are more aesthetically pleasing than hanging glue sticks or bottle traps from the ceilings. These lights also give the user the option of switching bulbs during the “off season,” if desired.

The large industrial fly light traps are manufactured in various sizes. They may have from two to four bulbs and emit anywhere from 30 to 80 watts of energy. And in food handling areas, shatterproof bulbs are required. These do not interfere with the light output but are more expensive.

The larger EFKs are quite expensive, and more than one is usually required. There have been several articles written on the placement of fly light traps, and discussing how many should be used in each account. In a simple diagram shown above, taken from an NPCA Technical Release, 12 light traps are used in a production facility. Besides the expense associated with using 12 traps, the pest control professional also has to monitor these each month, or in some cases, every few days. And if the traps are being used to reduce cluster fly populations, glue traps will have to be replaced frequently.

Maintenance of traps is also very important in making sure the lights are performing as they should.

As mentioned earlier, most manufacturers recommend replacing bulbs once a year. This is a good rule of thumb, but consider the situation where the ambient UV light has changed, or if new lights have been installed in a remodeled area. Either situation can affect the light competition, thus hampering the effectiveness of the fly light trap. Using the UV-A Meter may be a good idea to monitor these situations.

Cleaning and recording trap catches also takes time. Reports should be filed on what is being caught and what implications this may have on increasing sanitation problems or outside influences on the facility.

As with any pest control program, the success of a fly control and monitoring program, using fly light traps, is often related to the time spent at each job. And time is money.

George Rambo, a contributing editor to PCT magazine, is president of George Rambo Consulting Services, Herndon, Va.