Repellents as Part of Cockroach IPM

There is a time and place for the use of repellent pesticides as part of a comprehensive integrated cockroach control problem, according to PMPs interviewed by PCT.

Insecticide sprays for cockroaches work by exposing cockroaches to a chemical they absorb on contact, hopefully enough to provide a lethal dose. But should a PMP use a product that causes the cockroach to flee its hiding place, flushing it into a pretreated area, or attack them only in the spots where they are initially located as the PMP completes a thorough inspection of the client's site? As the Mallis Handbook of Pest Control notes, the increased activity of cockroaches after the application of repellents such as pyrethroids allows cockroaches to contact greater doses of insecticides and therefore increases the chance of cockroaches picking up a lethal dose.

Doug Foster, owner and president of Columbus, Ind-based Burt's Termite & Pest Control, says early in his career, "fogging" was the answer, driving the cockroaches out of their hiding places and exposing them to insecticide. Still, he uses repellents in some limited cases today. The challenge, he noted, is that repellents will merely relocate the cockroaches without killing them. "We do not want to move the cockroaches. We want to attack them wherever they're at," especially since cockroaches may simply move from one hard-to-access hiding spot to another, like a drop ceiling. This problem is especially relevant when working in multifamily housing units since relocating the cockroaches means involving another unit and another set of residents."

Foster says that in addition to performing a thorough inspection, it's often a good idea to talk to staff about problem spots before using repellent sprays. "In restaurants," he says, "the staff is there eight, 10, 12 hours a day. They have the experience to say where they are seeing the roaches, where they are coming from." But, with hard-to-find cockroach hiding spots, he says, once you've searched, talked to the staff, and taken apart a few equipment motors where roaches like to hide, sometimes the best choice is to "flush them out and see where they are coming from" while driving them toward an insecticide.

Mallis, citing the work of Brenner and Nalyana, calls this a "'push-and-pull' strategy to 'herd' cockroaches towards areas strategically baited or treated with residual insecticides."

Zach Smith, owner of Smith's Pest Management in the San Francisco Bay area, has another valuable way to use repellents: as a barrier to keep cockroaches from coming into the home from the outside. For many of his clients, a good perimeter placement keeps cockroaches entering a structure. Is your client a good candidate for this kind of treatment? Citing research by Appel and his colleagues, Mallis directs pest management professionals to pay attention to factors such as "tree density, number of pets," as well as the "age of the home," and "the number of obvious cockroach harborages on the property" to decide if this is a good strategy. As PMPs know, cockroaches are attracted to "dead and rotting organic matter," such as the kind of yard waste that builds up around homes in the fall and winter months.

Repellents, Smith emphasizes, should be combined with efforts such as making sure door sweeps are all in place and that other standard methods of entry have been obstructed. John Myers, A.C.E., of Gunter Pest and Lawn, Kansas City, Mo., agrees, noting that this sort of barrier protection is most suited for clients troubled by American and Oriental roaches.

Foster offers an important final reminder for those in the field. "Be careful when switching equipment" that is use for non-repellent and repellent insecticides. You don't want to simply cancel one out with the other. If the equipment isn't cleaned thoroughly between those two chemicals, the repellent's impact will be dramatically impeded.