Why are black beetles found in oatmeal

Recognize and fight grain beetles

Have you spotted small, brown bugs in your home among the food supplies? Then it could be grain beetle. Even if you feel disgusted, there is no need to worry. The small animals have nothing to do with unsanitary conditions and are relatively quick and easy to fight. Agricultural businesses and food manufacturers, on the other hand, should not waste any time and hire a pest controller as soon as possible.

Everything at a glance:

  • Corn beetles are small, up to 4 millimeters long beetles with a narrow body. Immediately after the transformation from larva to beetle, they have a light, red-brown color and get darker and darker with age.
  • They attack grains and processed foods made from grain.
  • Female grain weevils lay their eggs directly in cereal grains - one egg per grain.
  • You can recognize an infestation primarily by the crawling beetles. You can often find the source in the pantry. Classic foods that are infested are rye, wheat, spelled, barley, rice and corn.
  • In private households, these storage pests are rather a rare problem and easy to control with simple means.
  • In grain stores and food processing plants, however, a grain beetle infestation often degenerates into a plague that can endanger an entire harvest and destroy the grain supply. In such cases, the fight against it belongs in professional hands.

Appearance and way of life

The grain beetle (Sitophilus granarius) is one of the most important pests of grain and stored products. Pest infestation is a serious problem, especially for farms that store grain and mills, since the pests multiply very quickly, cause great damage and destroy an entire crop.

How do you recognize a pest infestation?

The most obvious signs are adult beetles crawling around the house. The Larvae on the other hand, you will hardly ever get to see them yourself, because these develop inside cereal grains and only eat their way out of them as finished beetles. Therefore, the spread of the pest usually goes unnoticed for a while.

The pests like rye best. But they also attack other grains such as wheat, spelled, oats, barley, malt as well as rice, maize, flour, bran, almonds, peanuts, peas, beans and soybeans. Not even grain pillows are safe from them.

As soon as you spot the small, brown crawling animals in your apartment, you should get yours Examine grain supplies. Females lay one egg each in a grain of corn. The larva hatches out of the egg, nibbles on the grain from the inside, pupates, becomes a beetle and eats its way out of the grain. The typical Holes in the Cereal grains you can see well. In addition, on grains from which no beetles have hatched, whitish plugs to recognize. This is a secretion that the female beetles use to close the opening in the grain after laying eggs.

By the way: In contrast to many other food pests, the adult animals of the grain beetles also use your food. So it's not just the larvae that nibble on the supplies.

Do you suspect that your grain may be bustling with grain weevils? Then put one or two hands of it in a bowl of water and stir several times. If grains swim at the top of the water, this indicates that the grains have been infected by the grain pest and are hollow on the inside.

What do grain beetles look like?

The pests are about 2.5 to 4 millimeters long and have an elongated, narrow physique. A furrow separating the abdomen and the pronotum can be seen in the middle of the body. The The head tapers towards the front and go into one Trunk over, at the end of which are the mouthparts. Young beetles are light brown to reddish brown in color. The older they get, the darker the shade of brown becomes, until they eventually turn a blackish-brown color.

Hind and front abdomen show a different one template on. On the abdomen you can see lines made up of dots in a row. The pronotum, on the other hand, has point-shaped depressions that do not form a linear pattern, but are arranged seemingly at random. The grain pests do not have any noticeable hairiness. The wings are also just a dummy, because the crawfish cannot fly.

The white, black-headed larvae are not even half a millimeter long and are therefore difficult to see with the naked eye. In addition, they develop into a finished beetle within a grain of grain and are therefore hardly noticeable in the stores.

Adult grain beetles are visually very similar to rice beetles and corn beetles and can easily be confused.

Do grain weevils harm your health?

Pests in the stores are unsavory. However, if you have eaten infected food, such as larvae or beetles, you do not need to worry. The little animals are not considered to be carriers of the disease.

However, pest infestation has serious effects on agriculture and in granaries. Here the animals can reproduce for a long time unnoticed and undisturbed. If the infestation is very strong, the activity of the animals causes the temperature and humidity to rise. That, in turn, can lead to that Mites settle or Molds arise. Both are detrimental to health.


Corn beetles are rarely found in homes, and when they do, the extent of the infestation is usually very low. In that case you will also be able to fight the beetles quickly. However, Sitophilus granarius is a serious problem for agriculture and the food industry. Fighting should always be done by a professional exterminator.

How can you control grain weevils?

Pest infestation in the home is rare and is usually not very pronounced. With a few hygiene measures, it will quickly become a thing of the past. You do not need to resort to chemical agents.

  1. Look for the source of the evil in your supplies. Throw all food that is infected in the trash, without exception, tie the garbage bag airtight and take it straight to the garbage can.
  2. Carefully vacuum all compartments of the infected cupboard or shelf with the vacuum cleaner. Don't forget about cracks, joints and other potential hiding spots. You should also dispose of the vacuum cleaner bag in the garbage can immediately afterwards.
  3. If you want to be absolutely on the safe side, you should then use a hair dryer to heat all gaps and joints. The heat kills the beetles that are still hiding there.
  4. Optionally, you can scatter kieselguhr in the affected cupboard or shelf, especially in the vicinity of typical hiding places. Diatomaceous earth is non-toxic to humans and pets, but it will ensure that the pests die.

Should you still find grain beetles in your home again and again Parasitic wasps a very good, natural method of fighting. They are completely harmless to humans and do their job reliably. Parasitic wasps are only a few millimeters in size, do not sting like their namesake and disappear on their own as soon as there are no more pests in your home.

When should you call a pest controller?

The control of grain weevils in farms, mills, granaries etc. basically belongs in the experienced hands of a professional pest controller.

Because the procedure described above is only suitable for combating a minor infestation. Of course, you cannot empty a granary. In addition, you are often faced with a real nuisance. Then even parasitic wasps will no longer help.

In such cases, a radical approach must be taken: This means that Grain that has been attacked destroyed must be and the empty granary or the silo with Insecticides needs to be treated. Pure fumigation alone is often not effective, as the larvae in the grains do not breathe and are therefore immune to any poisonous gas.

Causes and preventive measures

If you find grain beetles in your home, you have probably not done anything wrong, nor is it dirty or unhygienic in your home. In most cases you brought the animals home with you from the supermarket. A grain beetle infestation can basically affect every household.

How do grain beetles get into the apartment?

Grain beetle can't fly. You can rule out that they fly in through the open window, attracted by fragrances or light, as does the bread beetle, for example.

When you spot the grain beetle in your house, you usually have it unnoticed with yours Shopping from the supermarket brought home. As a rule, the pest infestation is only weak and you can get rid of the few beetles relatively easily.

How can you prevent an infestation?

A grain beetle infestation does not occur because the conditions in your home are unsanitary. Corn beetles get into your home in food packaging from the supermarket by chance and unnoticed. Since you haven't done anything wrong, it is hardly possible to prevent grain beetle infestation.

However, they can make it more difficult for the beetles to spread in your pantry. Best to fill in all of them Food after shopping in airtight plastic containers or glasses around. If there are pests in a package, they cannot spread to your other supplies.


Corn beetles are one of the most important grain pests. In private households they only play a subordinate role, as they are rarely found here. You can usually fight these quickly and easily.

However, they pose a serious problem for agriculture and the food industry as the pests can destroy entire crops. In addition, an infestation often goes undetected for a long time and the beetles can reproduce undisturbed. Often the only way out is to destroy the infected grain and to free the grain store from the last beetle and the last larva using appropriate chemical means. Fighting should always be carried out by an experienced exterminator.