German Cockroaches – The Public Health Pest In Your Home
Written by Anthony O’Neill – Licensed Pest Management Professional
The German roach (Blattella germanica) is the world’s most common and troublesome domestic species of cockroach to infest where we live and work.
These filthy pests carry harmful bacteria which they leave on our food, countertops and anywhere else they crawl across. And if that’s not bad enough, they are prolific breeders and produce hundreds of nymphs in just one year!
German cockroaches spend around 75% of their time hiding in tiny cracks and crevices in areas close to food sources and water in your home, so you might not know you have them until the infestation grows.
Read on to find out where you can find them, how to identify them, the signs of an infestation, and what you can do to try and keep them out.
What Do German Cockroaches Look Like?
This species of roach is the top pest found in homes, multi-family housing, rental properties, and commercial kitchens.
German cockroaches live indoors alongside us and thrive in the warmth and humidity of our homes. So what do they look like?
Adult German Roaches
- German roaches belong to the group known as small cockroaches as they are about ½” – ⅝” (12.7 – 16 mm) long
- They have oval bodies with six legs and two long antennae
- Adults are light brown to tan color
- They have two dark parallel stripes on their pronotum (the shield-like area behind their head)
- Adult males have narrower bodies than the females
- Females are slightly darker than the males
- They have fully developed wings, but do not fly
German Cockroach Nymphs
- Nymphs are about ⅛” (3 mm) long when they emerge from the egg case or ootheca
- Baby roaches are white and their bodies are soft when born and after each molt, but turn dark brown to black in color once their exoskeleton hardens
- They have dark-colored stripes on the pronotum
- Nymphs do not have wings
German Cockroach Life Cycle
As with all cockroach species, the german roach undergoes the same three stages of incomplete metamorphosis, which are: egg, nymph, and adult.
German Cockroach Eggs
The light brown purse-shaped egg sac is 1/4 – 3/8″ (6.35 – 9.5 mm) long and 5/64″ wide (2 mm), and contains between 30 – 48 eggs.
The female carries the egg case or sac (ootheca) partially inside her abdomen for around 28 days and drops it somewhere safe and away from predators a day or two before it hatches. This makes it difficult to spot them, especially in the early stages of an infestation.
If the female drops the egg case before the nymphs are ready to hatch, they will not emerge and die of dehydration.
Baby German Roaches
What do baby cockroaches look like? They look like the adults except for their size which is obviously smaller. The other difference is the lack of wings.
I took the photo below when treating a heavily infested property and you can see the adults and the nymphs which are of various sizes hiding in a cupboard door hinge.
When the nymphs hatch from the ootheca they have soft, white bodies and are tiny in size at about 1/8″ (3 mm) as mentioned above.
After a few hours, their bodies harden and change to a dark brown/black color.
These juvenile roaches are hungry and soon go looking for food.
At room temperature and with enough food and moisture, baby roaches reach adulthood in around 100 days.
During this time they grow which means they go through 5 – 7 nymphal stages (instars) where they molt and shed their exoskeleton each time to make room for their growing body.
Roaches are also white after each molt (aka ecdysis) but become darker over a few hours once pigmentation is restored.
When the cockroach nymph molts it finds an area to hide where it will be protected from predators.
As the exoskeleton is rigid, the nymph has to take in large amounts of air during a molt so it can inflate its body to split and shed the outer cuticle.
They have two dark parallel stripes on their pronotum, the same as the adults.
Baby roaches become adults when the final molting stage takes place. The newly emerged adults have wings and can now mate and reproduce at an alarming rate.
Adult German Cockroaches
German roaches have the highest rate of reproductivity of all the common cockroach species, and they certainly produce a lot of offspring.
As said above, after mating the adult female produces an egg capsule containing 30-48 eggs. And at room temperature, this same female will keep producing an egg capsule every 6 weeks.
This means she will produce between 6-8 egg cases in just one year, with an average of 350 offspring!
And if that’s not worrying enough, it’s reported that a single female and her offspring can produce over 30,000 individuals in a year.
This rate of reproduction explains why an established infestation can get out of hand very quickly as it comprises around 75% nymphs and only 25% adults.
The average life span of both adult male and female german roaches is between 100 – 200 days (males typically around 130 days and females around 150 days), but in that time they can create a rapidly growing infestation.
Female adult German roaches are slightly larger and darker than the males and have a rounded, wider abdomen so they can carry the protruding egg case.
Signs of a German Cockroach Infestation
These little cockroaches thrive in areas where there is heat, humidity, and moisture.
In the early stages of an infestation, German roaches will usually only be found in the kitchen and bathrooms because these provide access to water and moisture through leaky taps and pipes, and warmth from heat-producing appliances, such as a refrigerator.
However, as the cockroach population grows they will spread out to other areas of the home.
Here are some telltale signs of a roach infestation:
As these small cockroaches look for food and scurry across your kitchen countertops and inside your cabinets and drawers at night they leave behind their droppings (frass).
German roach droppings are easily identified because they look like coffee grounds or ground specks of black pepper. In fact, roach poop looks similar to bed bug feces.
At first, most people are unaware it’s roach feces because it’s unlikely you’ll see these pests during the day unless you have a large infestation.
The following image is one I took that shows where they have congregated as there are plenty of droppings and fecal stains.
Smear Marks/Fecal Staining
Another sign to look for is any dark staining or smears in corners of the walls, in and around cracks in walls, under the refrigerator, on the tops of doors, and in other areas where they cluster.
These areas are marked with an aggregation pheromone found in their droppings which attracts other roaches to cluster in these areas.
As you know, the German roach egg cases are tiny but you can find these light brown, oblong-shaped casings if you look carefully.
Places to check are anywhere there is a crack or crevice, such as in the walls, in drawers, and door hinges and trims.
Each egg case can have up to 48 developing nymphs inside it and they will split the case open and emerge leaving the empty egg casing in place.
With that many roaches being born at the same time, you have some idea why cockroach infestations can grow so quickly.
Seeing Roaches In The Daytime
If you see a roach or roaches scurrying around your kitchen or bathroom during the day, then this is a good indication that you’ve got a large infestation in your home.
These pests usually only come out during the day if their hiding areas have become overcrowded and they need to find somewhere to shelter.
As their population grows, it becomes harder for them to easily access food and moisture so they have to come out and search for them in other areas.
Other indications of a heavy infestation also include finding dead roaches and shed skins left behind during a molt.
German Cockroach Allergy
This isn’t something I’ve heard any of my customers mention but it’s actually not uncommon to be allergic to roaches.
Proteins found in the droppings, shed skin, and saliva that they leave behind on surfaces, utensils, and food not only can cause an allergic reaction but can also trigger asthma, or make it worse in both adults and children.
The allergens can cause:
- Itchy nose and eyes
- Stuffy nose
- Skin rash
Even if you don’t see any cockroaches in your home, a roach allergy could be something to consider if your allergies are lasting longer than the usual seasonal allergies.
What Do Cockroaches Smell Like?
Can you smell a cockroach infestation? Some people notice an unpleasant odor when the infestation is fairly big, but others don’t detect a cockroach smell at all.
The odors are produced by several things including decomposing dead cockroaches. When a roach dies, its body produces oleic acid which is a foul-smelling odor that other cockroaches stay away from.
Other roach smells are caused by pheromones produced in the fecal droppings. These secretions are used as forms of communication to aggregate other roaches to an area or to attract a mate.
The best way to probably describe the smell is as pungent and offensive that has a heavy, sweet, oily, musty odor. But as I said there isn’t always a noticeable smell.
Where Do German Cockroaches Hide?
I’ve mentioned before that I always look and find an infestation behind the refrigerator and the other place where I usually find them is on cupboard door hinges.
German roaches tend to congregate within 12 feet of where there is food and water and they need a lot of water to survive, so their harborage areas tend to be in our kitchen and bathroom.
They prefer porous surfaces such as wood and cardboard instead of surfaces like metal. I find many cockroaches hiding in kitchen appliances, drawers and cupboards
The following list also gives you some others of where else you might them:
- Behind and under the refrigerator, freezer, dishwasher, washer and dryer, stove/oven, water heater, kettle, microwave, and other appliances that have a motor to generate heat.
- Look in the dishwasher and stove
- Look under sinks for leaky pipes and where the pipes enter through the wall
- Inside, underneath and behind cupboards, cabinets, and drawers and the corners of these
- Cracks around cupboards and drawers
- Cupboard and door hinges and frames
- Oven door hinges
- Behind cracks in baseboards and moldings
- In window frames especially if there is condensation on the windows
- In wall voids behind the sink, dishwasher, or oven
- In electrical equipment such as the TV, clocks, computer, and behind electrical sockets
- In the pantry, grocery boxes, and other food containers
- Trash cans
- Cracks in tiles
As German roaches are so small, they can hide their flat bodies in the smallest cracks and crevices.
These insects prefer warm, dark, quiet places and as long as they have access to the four basic requirements of water, food, warmth, and shelter, they will be able to hide during the day undetected.
How Do These Little Cockroaches Get Into Our Homes?
People often think that roaches are only found in unclean homes, but this is not always the case. Having said that, good sanitization is vital when trying to keep your home cockroach-free.
However, it might not matter how clean you keep your home if you live in an apartment building because roaches can spread to nearby units through gaps around pipes and along utility lines.
More often though they are brought in with your deliveries, in your grocery bags, luggage, cartons, used furniture, and electronics. You can read more here.
What Are German Roaches Attracted To?
This species of roach cannot survive outside in the cold, so our homes provide the warmth and shelter that they need.
But just like other pests, they also need food and water sources to survive and the list is almost endless as to what can be an attractant because these roaches will eat just about anything.
So by removing these sources, especially water, you will prevent the population from growing.
In fact, German cockroaches need water more than food to survive. So limiting access to moisture and water sources should be a top priority.
Below are examples of some of these sources that act as attractants, but make sure you check out my more detailed list of what attracts cockroaches to your home so you can thoroughly check your home.
- Dripping or leaking faucet
- Dishes left in sink overnight to soak
- Food and pet food left out overnight
- Spills not cleaned up
- Crumbs not cleaned up
- Standing water in bathtub
Can German Cockroaches Make You Sick?
Roaches eat and crawl through all sorts of filth and rotting matter and pick up disease-causing bacteria and viruses on their spiny legs and bodies.
We can become ill if our food and other things we touch are contaminated when a roach crawls across it to forage, or when they leave their droppings and saliva behind.
Although German roaches have not been documented to cause an outbreak of an illness, they are still considered a dangerous public health pest as evidence suggests they can spread 33 types of bacteria including E. coli and Salmonella which can cause food poisoning and diarrhea.
This is no surprise really because as I’ve already said this insect will eat almost anything, and that includes other dead roaches, regurgitated food, and their own feces!
So for anyone who has ever wondered ‘are cockroaches dirty?’, you know have your answer.
And as if that’s not bad enough, there are also the allergy problems from their shed skins and droppings that I mentioned above.
Controlling German Roaches
The German cockroach is known as a common household pest and can be hard to treat. You now know that they are prolific breeders and they are the one pest that can cause a massive infestation fairly quickly.
If you want to do your own cockroach pest control then start by excluding their entry points and hiding areas and eliminating their food and water sources, which you can find out about by reading what attracts cockroaches.
Sticky traps will help you find where their harborage sites are as well as monitor their population level.
Vacuuming is good for immediately reducing their numbers and will also remove their eggs and droppings. A vacuum with a Hepa filter is recommended to reduce the amount of airborne roach debris that can cause allergic reactions.
Professional grade cockroach control products such as gel baits can be placed in small amounts directly in their harborage areas and in cracks and crevices. These baits are effective in killing german roach infestations.
On the other hand, if you are seeing roaches in your home during the day, then I recommend calling in a professional pest control company as you’ve probably got a large population of roaches that you might not feel comfortable trying to deal with.
What are cockroaches?
What attracts cockroaches to your home?
This is why you see cockroaches outside your home and in your yard
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