Cockroaches leave bacteria behind



Cockroaches are rightly considered one of the worst plagues. Due to their way of life, they are also increasingly acting as carriers of diseases. Ingested pathogens are wiped off everywhere. Bacteria and germs can also be found in the cockroach droppings that are left on food, appliances, furnishings and the like, which not only make the food unusable, but can also cause disease.

In addition to the material damage (resulting from the costs of control, additional hygiene measures and the destruction of food) that a company suffers, the loss of image is often even more significant when a cockroach infestation becomes known.



The "German cockroach" (Blattella germanica) is one of around 3000 species of cockroach. She is one of the cosmopolitans, that is to say: she appears worldwide. As nocturnal creatures, cockroaches are rarely found during the day. They can be found in all sorts of cavities, in the motors of refrigerators, cooking groups, behind cladding, loose tiles, rubbing and bumper strips, etc.; in short: all hiding places in the immediate vicinity of water and food are used. As soon as the operating rooms are quiet, the cockroaches venture out of their hiding places and go in search of food and water.



Cockroaches lay packets of eggs in which the "German cockroach" contains 20-48 nymphs. The egg packet (ootheca) contains a number of chambers inside, in which the larvae reside, as well as a nutrient substrate. The chambers and nutrient fluid are protected by several layers, with the outer shell being a pure chitin layer and therefore completely impermeable to insecticides of any type and shape. If no appropriate control measures are taken when a cockroach infestation is detected, their number can explode. Based on a period of 20 weeks, the multiplication potential is 400,000: 1 (see model calculation below).

The nymphs leave the egg package after about five to six weeks, then moult up to seven times and become sexually mature themselves after about four months. The ootheca is usually stored in inaccessible places so that these cannot be reached and removed during cleaning.


Prevention and control

Successful control measures depend on various criteria. The most important are:

• a 100% hygienic condition
• Finding all hiding places
• Knowledge of the client company
• Knowledge of its suppliers
• Knowledge of the transport routes etc.


Strategic approach

At this point it should be pointed out that when combating cockroaches (this also applies to the control of other pests), the active substances must be changed at regular intervals in order to prevent the development of resistance.


Computer model calculation

Influence of "efficiency" and "frequency" of the control on the development of a colony of 100 freshly hatched males and females of the German cockroach. Empirically determined average values ​​are assumed for the rate of reproduction, natural mortality without control, capsule cycle and duration of the young stages