There are several considerations that come into play in any discussion of cockroach control. The first is understanding how infestations arise. The usual modes of entry for German and brown-banded cockroaches are through infested parcels containing food or other materials, and by movement from abutting dwellings. Most of the other, larger pest species tend to live outdoors and can move from one building to another. They can also be introduced in parcels. Thus, the next consideration is prevention of entry. All entering parcels should be inspected to be sure they do not contain cockroaches, and dwelling defects should be corrected to exclude invaders. Finally, human living space should be kept free of clutter, which can act as hiding places for cockroaches, and food left on dishes, in sinks, or on floors, which can feed a population of cockroaches, should be disposed of properly.
When infestations occur, there are two main methods of control. Nonchemical methods include trapping and vacuuming cockroaches, both of which can significantly reduce the size of an infestation. In addition, freezing, overheating, or flooding structures with a nontoxic gas can be used to kill the pests. Some of the latter procedures require specialized equipment and are best done by professional pest control operators.
The most common method of control is the use of chemical poisons. A large variety of insecticides exist that will kill cockroaches. Some of them are contact poisons that are absorbed as cockroaches walk over treated surfaces. The most common of these belong to the chemical classes called pyrethroids, organophosphates, and carbamates. They kill by disrupting the insect's nervous system, each in a specific manner. Other insecticides are administered in bait formulations that must be eaten by the cockroach. Among them are avermectin and fipronil, which also attack the nervous system, hydramethylnon, which disrupts cellular respiration, and boric acid, which destroys the cells lining the insect gut wall. Each of these materials, as well as others not mentioned, has its own chemical characteristics and must be used in accordance with label instructions.
New insecticides are regularly being introduced that can kill cockroaches, and older ones are being phased out. A critical goal is to develop safer chemicals and safer methods of applying them. For example, the older practice of applying insecticides to surfaces over which cockroaches are expected to crawl is being used less frequently and, as a consequence, the organophosphate and carbamate insecticides especially are being phased out. The practice of dispensing chemicals as baits has largely replaced the surface application method. With baits, the insecticide is more confined and the safety (of humans and pets) is thereby enhanced. The use of baits has become practical in recent years because some of the newer chemicals are highly palatable for cockroaches in bait formulations.
Cockroach control in the future will likely depend on the availability of new insecticides as well as the development of better methods of applying them. Among the approaches that are possible is searching for chemicals that act on sites not previously exploited. For example, a combination of two chemicals is known that prevents cockroaches from producing uric acid. Previous research has shown that storing and recycling the chemical constituents in uric acid is critical to the survival of cockroaches. The functioning of this system is dependent on the fat body endosymbiotic bacteria, mentioned earlier. Other points of metabolic vulnerability will also probably be found in the future.
Another reason for the need for new chemical approaches is that the most important cockroach pest, B. germanica, has become resistant to many of the older insecticides. When this occurs, either the effectiveness of those chemicals is greatly reduced or they become useless against resistant populations. With continued use of the newer chemicals, resistance to some of them will probably develop. A steady supply of new chemicals with new modes of action will greatly alleviate this problem and facilitate continued control.
See Also the Following Articles
Isoptera • Medical Entomology • Orthoptera • Phasmida • Urban Habitats
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