The German Cockroach: An Endangered Species

After millions of years of co-evolution cockroaches remain the nemesis of humans and their habitations. Throughout the ages humans have thrown everything imaginable at this pest, and to no avail. Even as an industry possessing the ultimate weapons of doom, we have failed to bring cockroaches, particularly the German cockroach, to the brink of extinction.

At least 100 years ago, sodium fluoride was used to control cockroaches, as well as other structural pests. As early as 1919, the use of boric acid to control cockroaches was researched and reported in the scientific literature. In the 1940’s we thought DDT, chlordane, and other chlorinated hydrocarbons would spell the end of the species. Since then we have seen the development of organophosphate, carbamate, and pyrethroid insecticides, as well as insect growth regulators, chitin synthesis inhibitors, parasites, predators, etc. Yet this species persists. In fact, it flourishes.

We must stand back and admire the resilience of the German cockroach, as it has continued to evolve and adapt, despite everything we can possibly throw at it. There are many reasons for this species’ durability, but likely the most important factor is its biotic potential, i.e., its ability to generate large numbers of offspring in a very short period of time. A female can produce four to eight oothecae (egg capsules), averaging 18 to 50 eggs each. They can go from egg to adult in an average of 103 days (NPCA Field Guide to Structural Pests). Thus, a pair of German cockroaches could generate 575,000 offspring in one year if all were to live.

This biotic potential is also why the species develops resistance to insecticides very quickly as compared to other cockroach species, which rarely exhibit any resistance. The degree to which resistance contributes to the species’ survivability is a debatable issue, and we need to keep in mind that resistance is unique to a population and not to the species. Resistance varies by degree and product in isolated populations. Our industry has perpetuated the development of resistance in German cockroach populations by indiscriminately applying pesticides on a scheduled basis, often two, three, and four times per month with no thought as to what products are being used.

German cockroach control failures are not something that pest management companies or their customers should have to accept, and with the plethora of tools we have at our disposal, there is no reason these “resistant populations” cannot be eliminated. The most effective method of combating resistance in German cockroaches is population elimination. Eliminating a resistant population destroys the gene pool that created resistance patterns observed in the population. And there are many ways populations can be eliminated.

Inspection and monitoring. Technicians must take the time to look for and identify all potential harborage sites. They must learn to look at the whole site and not just from the waist down. They may have to do some work at night. Areas of poor sanitation must be identified. Points and routes of entry must be identified and traced to the source.

And it’s not enough to just inspect. Technicians must maintain the vigil by constant monitoring for new developments, introduction of new populations, and the progress of the pest management plan.

Sanitation. This cultural practice is the responsibility of the customer and is critical to the success of the pest management plan. Good sanitation removes the cockroach’s essential resources: food, water and harborage.

Physical removal. No pest species is resistant to physical removal and destruction. This is accomplished through trapping and vacuuming.

Heat. German cockroaches readily succumb to desiccation, which results from exposure to temperatures higher than 120°F. The higher the temperature, the quicker they die.

Caulking. A relatively new strategy for our industry, caulking eliminates harborages and stresses the population. Insect growth regulators. These extremely volatile and mobile molecules prevent reproduction in the population and increase the effectiveness of baits by stimulating feeding. Significant resistance to these products has not been reported in the literature.

Baits. Baits put palatable and attractive active ingredients close to the population. No significant degree of resistance to avermectin, hydramethylnon, and boric acid baits have been reported.

Directed insecticide applications. Directed applications involve thorough crack and crevice applications, and there are many effective products and new active ingredients in the arsenal designed for this purpose. Acephate is one of the older products to which resistance in German cockroaches has failed to develop. Technicians must be able to select the appropriate formulation for the site.

Creativity. Not to be overlooked, creativity involves our ability to think, determine the foci of infestations, and design a pest management program that successfully eliminates the population.

We have all the tools, the knowledge, and the ability to place the German cockroach on the endangered species list. However, we need not fear that we are going to put ourselves out of business because, in the end, the cockroach has always won.

Dr. Richard Kramer is president of Innovative Pest Management Consulting, 18100 Darnell Drive, Olney MD 20832, 301/570-7138.