Flushing With Air: A New Tool For PCOs

Pest management professionals often wonder how a trace of pyrethrins can make a cockroach move as fast as 40 miles per hour.

Biologist V.G. Dethier has some answers in his book, The Physiology of Insect Senses. According to Dethier, the abdominal nerve cord of the American cockroach is actually bigger than its equivalent in mammals. Dethier further describes the several mechanisms with which insects survive in a hostile environment. These include mechano-receptors (for detecting movement), various chemo-receptors, sound reception, photo reception and humidity receptors. He outlines the complex neural circuitry involved in each mechanism.

FLUSHING WITH AIR. Of these, I always considered chemo-receptors responsible for the flushing action of pyrethrin/pyrethroid products. That may, in some cases, be a myth conception according to an article by Oswald, Apple and Smith in the April 1997 edition of the Journal of Economic Entomology. The article, entitled, “Repellency and Perception of Moving Air by the German Cockroach,” describes how moving air alone can repel German cockroaches. Using modified Ebeling choice boxes, to test choices in behavior, the researchers experimented with some German cockroaches that had their antennae removed, and with others that had their cerci removed. The result showed that with the German cockroach, the antenna was the primary sensory organ of wind detection.

This was interesting to me because I recall an experiment done by J. H. Camhi at Cornell in the ’80s in which he showed that the cerci (pair of appendages at the rear end of the cockroach) of American cockroaches was the primary site for mechano-receptors. In the experiment, a toad was placed in a 3-foot chamber in a pitch dark room. A high speed infrared camera captured the action with 64 frames a second as an American cockroach was placed in the cage.

The cockroach escaped the quick zap of the toad’s sticky tongue. However, the cockroach could not escape the toad’s zap after Camhi waxed the cockroach’s cerci.

Apparently the direction of the slight movement of air caused by the movement of the toad and its tongue told the cockroach which way to escape. Camhi found that the escape response can begin within 11 milliseconds after the hairs on the cerci move.

In a 1980 Scientific American article (“The Escape System of the Cockroach”), Jeffrey Camhi described early studies in which 220 delicate hairs on the bottom of each of the cerci responded to wind, which excited the cockroach to run. German cockroaches, on the other hand, have most of their mechano-receptor hairs on their antennae. The German cockroach typically rests in a narrow crevice or harborage with its antennae extended out from the crevice, thus monitoring the environment outside the crevice.

TOOLS FOR THE FUTURE. As the new century approaches, some of our pest control practices will be outmoded. Pressure from environmental groups has prejudiced the public attitude against the use of pesticides, however safe they are in relation to humans and pets.

As a result, pest management professionals will be spending more time monitoring than treating. Greater use of industrial vacuum cleaners, entrapment and exclusion devices will also come about because of public pressures not to use pesticides. Using baits and minimum amounts of least toxic pesticides will become the norm.

Now a new tool, the use of air, may be commonplace. Air curtains to exclude flying insects have been around for decades. Dr. Eric Smith, author of the NPCA Field Guide to Structural Pests, has for years used an aerosol can of plain air to flush cockroaches from harborages in sensitive situations such as in pet shops, schools, electronic equipment, etc. But more sophisticated tools creating directed, sustained pulses or intermittent breezes into familiar foci of cockroaches and other pests is likely to be added to the 21st Century arsenal for our industry. Oswald et al. suggested the development of systems that blow air steadily into kitchen and bathroom cabinets, wall voids and equipment.

A STREAM OF HOT AIR. Most domestic cockroach species spend most of their time in dead air cul-de-sacs where their water balance is not in danger. They emerge at night onto a kitchen floor because the air is cool, moist and quiet, and there are no breezes from open doors, fans or moving people.

Oswald et al. have shown how repellent a breeze can be to the German cockroach. If a device is developed which could add heat to an air stream that is directed into the known or suspected foci in sensitive areas, the cockroaches would be forced to move elsewhere to less sensitive areas, where they could be baited and trapped. This procedure would be a natural for those installations where zero tolerance for even low toxic pesticides is specified. A shot of diatomaceous earth preceding the hot air treatment would indeed leave a permanent, hostile environment for most arthropod household pests.

Lest anyone be carried away with the idea that the cockroach problem would be finally solved with this or any system, it might be appropriate to remind PCOs of what Bill Buettner, the NPCA’s first secretary, once told some PCOs when DDT hit the market: “Better find a new way to make a living. This DDT stuff is going to wipe out all the pests.”

Harry Katz may be contacted at Berkshire E-3076, Deerfield Beach FL 33442.