German Cockroach

large image of german cockroach


German cockroaches, Blattella germanica, are one of the most common urban insect pests throughout the world. This species of cockroach prefers to live in a humid atmosphere with an average temperature of 70º F (21ºC). Since these are the same conditions preferred by man, it is no wonder that German cockroaches have adapted to living in man.s home, office, ship, restaurant and school. Having had a longer track record of survival on the planet earth (300 million years versus 1 million years for man), it is thought by many that cockroaches are likely to out survive man in the long run.

Cockroaches are known mechanical vectors of bacteria and other diseases; their fecal material, hairs and cuticle are the source of allergies and asthma for many, and their odor is described as unpleasant, but their most objectionable characteristic is their tendency to appear uninvited at the table. Long considered a sign of poor sanitation, cockroaches are now identified as a public health issue.

Interesting Facts about German Cockroaches:

Cockroaches have been found in the fossil record as far back as 300 million years and the largest fossil, from Ohio, measures nearly 3.5 inches long There are about 3,500 cockroach species world-wide, about 70 of which are found in the United States. The egg case or ootheca contains about 40 eggs lined up in a double row.


There are several pest species of cockroaches found indoors and many more non-pest species found in nature. It is important to identify your cockroach. German cockroaches are about ½ inch in length, brown in color and have two dark parallel streaks running longitudinally down the thorax. These dark streaks are present on nymphs (the earlier stages without wings) and on males and females. The female carries her eggs (20 to 50) in an external capsule which in time becomes as large as her abdomen. The nymphs go through seven molts in a two month period before reaching sexual maturity and bearing wings. These cockroaches are found in kitchens, bathrooms, and in other locations with moisture and food.


Although German cockroaches are attracted as nymphs to the odor of fecal material and as adults to each other, in all life stages the main attraction is food. Even a clean, sanitary area will have sufficient food to sustain a few cockroaches so that it is most difficult to eliminate an infestation through restriction to food alone.

An important task is to identify where cockroaches are hiding during the day since they are primarily active at night. It has been found that the average cockroach prefers to wedge itself into a crack about ¼ inches wide. Since there are numerous cracks of this dimension in any normal setting and since food is also generally plentiful, cockroaches can hide in some very interesting places. Examples include behind electrical plates, inside water coolers, under wall moldings, behind walls, and in plumbing and pipe chases. Of course when cockroaches are more abundant, they will also hide in folded paper bags stuffed next to refrigerators, inside radios on kitchen counters, inside wooden knife holders, under the rim of sink fixtures, and even in recipe boxes.

Moisture is critical to cockroach survival so breeding usually takes place in kitchens and bathrooms although adults may be found in any room. When a single adult is found climbing up a wall in an office during the day and the office does not have a sink or other water source, than it is a good bet that the cockroach was recently introduced into the office from another infested site. This cockroach could have come out from under the wheel casters of a cleaning cart, crawled through plumbing lines from a neighbor or was flushed into the area because of the use of insecticide sprays at another location.


This fact sheet discusses how to keep German cockroaches out of urban settings by using Integrated Pest Management (IPM) techniques rather than by spraying insecticides, chemicals which eventually can be more harmful to man than to cockroaches.

By careful monitoring of cockroach population numbers and breeding locations, you can evaluate the success of different control methods and come up with the best balance of several successful IPM technologies.

The following steps have proven to be successful in controlling German cockroaches under most circumstances when carefully applied.

Use sticky traps to monitor population levels and to identify breeding locations. Hot melt adhesives (non-volatile glues) are excellent surfaces for capturing cockroaches. The trap surface must be tacky enough to hold these light insects as they scamper onto the glue. In recent years there has been considerable improvement in the design and function of insect sticky traps. Set several sticky traps around at floor level and others near sources of moisture. Click to see some traps

Temperature extremes are excellent tools for preventing normal life cycle activity. Very hot temperatures (140ºF for several hours) have been licensed under technology in some states for the control of cockroaches. Elsewhere museums are using cold storage (below freezing for 24 hours) to decontaminate artifacts.

Baits are very effective, in recent years the improvements in bait formulations has resulted in dramatically reduced cockroach populations. The toxicant may very from bait to bait as well as the food based attractants. Synthetic hormones in baits show value in locations where bait stations cannot be used due to extreme conditions of moisture. These chemicals interrupt the molting process and prevent cockroaches from reaching adulthood. Over time, resistance may develop to either the bait attractant or to the toxicant but today, baits are producing remarkable results. Baits in containerized distribution units are more expensive and less flexible than the bait formulations applied with a caulking gun. However, the baits in containers are less likely to be exposed to the public or the environment and may stay fresh longer. Click to see some baits

Desiccants powders and dusts have replaced sprays during the last decade but their greatest limitation is that they can only be applied behind walls and into voids and similar locations. Reducing moisture is always a positive step. Repair any drips or water leaks and try to avoid using a water hose under high pressure to clean an institutional kitchen. Clean up clutter wherever it is found, including paper bags behind and on top of refrigerators, items that fall behind drawers, and cardboard boxes.


Due to the public’s concern over the safety of pesticides and the desire to find alternatives, some individuals and companies are selling devices for the control of cockroaches that have questionable value except for the value to their own pocket book.

Ultrasonic devices: cockroaches are not repelled by ultrasonic sounds; they do however have the potential to disturb dogs and other animals that can hear in this range.

Electromagnetic devices: may increase activity levels of some insects but do not repel cockroaches. Expensive electric traps: cost up to $300 and catch no more cockroaches than a smaller 50 cent trap which is more easily replaced.

Questionable guarantees: claims of 100% control, .safe for everything except pests., and statements that cockroaches have nests when in fact they do not.


If you prefer to use a pest control professional, then the following guidelines should help you choose a reputable firm.

Obtain two or more estimates for control. The company you choose should have experience in using IPM in an urban location. Do not accept the alternating of chemical sprays as a definition of IPM.

Is safety measures part of the pest control service? Are you provided with a material safety data sheet or sample label that indicates hazards and are you given a fact sheet on cockroaches?

If the infestation is successfully eliminated, there is little concern that you will need additional service such as a yearly or monthly service. Be wary of signing a contract that requires additional costs and service.


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