Questions & Answers

Q: We routinely treat attics for cockroaches, silverfish and rodents. Occasionally, we’ve found dead subterranean termite swarmers in attics, which alerted us to infestations below. Attics can be difficult and dangerous areas to inspect and treat. What are your recommendations? (B.P.)

A: Attics vary considerably in their construction and importance to residential pest control. For example, in the South, attics almost always have to be considered in an overall pest management plan.

Typically, they are open in a variety of locations to provide ventilation, which also allows pests easy access. Often the attic environment is very suitable for insect infestations. If proper ventilation is not utilized, attics become serious reservoirs for cockroaches, silverfish, some fabric pests and rodents. Additionally, many people use the attic as a storage space, which further complicates the inspection and treatment of this area. Also, in the South the attic is frequently the location of the central air conditioning and heating system for the dwelling.

Clearly, the safety issue should be of major concern to all personnel working in this space. Sooner or later, if you spend much time in attics at all, you will put a foot, leg or in extreme cases, your entire body through the ceiling of someone’s home. This, of course, should be avoided. If ceiling joists are not visible or if there is no decking of the attic floor, you must be very careful when working in this area.

It occurs to me that the attics of most houses are ideal locations to practice habitat modification. For example, ventilation should be maximized, particularly for homes in the South. Air movement is not consistent with favorable insect harborage. The use of soffit vents along with ridge vents probably provides the best form of ventilation. Also, if homeowners are going to store items in attics, they should probably not be in cardboard boxes. Instead, items should be in sealable plastic containers or bags to minimize insects and rodents using these containers as harborages.

Truthfully, storage of household items in attics should be discouraged. I would recommend that the most thorough and extensive treatments of attics take place during the initial treatment. For years dusts have been used as one, if not the primary, treatment formulation for attics. These products have been applied in one of two general ways: First, the attics have been volumetrically dusted using power dusters. This method is to be discouraged. While it may control insects, it also contaminates everything, including the HVAC system and all stored items. And under the worst circumstances, the dust can filter into the living space below. The second most common method is to use a hand duster to apply dust to strategic locations such as soffit areas and ridge lines. This is a far more conservative approach but requires that the technician move about in the attic, which increases the potential for an accident.

Lately, many companies are switching over to the use of cockroach and ant baits in attics, applied as gels or granulars. These formulations can, in part, allow the technician to treat the attic space without having to move throughout the attic. In some types of construction, treatment of the soffits can best be achieved from the exterior perimeter of the home. Placing bait materials directly into the soffits through the soffit vents eliminates the need for technicians to crawl into these very tight and dangerous locations. If dusting is chosen as a treatment method, then in many cases the soffit areas can also be dusted from the exterior perimeter by injecting dust into the soffit around ventilation openings or by drilling and providing access to these strategic areas.

In some parts of the country, companies have been fogging or applying ultra-low volume treatments to attic voids on an annual basis. This method can be effective but, of course, provides no residual activity. Also, if pilot lights are found on HVAC systems in the attic or if gas-powered hot water heaters are located there, extreme care should be taken when using this method. When selecting dusts for attic application, I lean toward using inorganic materials such as boric acid and silica gels because of their relatively inert nature and long-lasting residual activity. There are several other pyrethroid-based dusts which are also effective.

If attics are treated thoroughly initially, then there should not be any need to provide ongoing treatment, particularly if habitat modification is also practiced. Providing adequate ventilation is the first step. Keeping pests from entering by sealing cracks and crevices, and the use of a screen is also important. Trimming shrub and tree branches away from eaves can also help, and thorough exterior perimeter treatments at ground level will reduce the potential for insect migration.

Finally, monitoring of the attic can be achieved using various types of sticky traps. Glueboards placed strategically around stored items or in harborage areas are recommended. The locations of these monitoring devices should be mapped so technicians servicing the structure will know where to find them. Also, some type of flying insect monitoring system would be appropriate. One relatively inexpensive and very effective way for monitoring flying insects, including subterranean and drywood termite swarmers, is the Spider Web Fly Glue Trap from Catchmaster. One of these devices can be hung from the ridge lines at either end of an attic space and examined during each service interval. The use of monitoring devices in the attic can reduce the frequency of pesticide application and reduce the amount of service technician activity in this potentially hazardous environment.

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