Wheat Weevils


  • Scientific name: Sitophilus granarius
  • Size: 1/7th to 1/5 an inch
  • Color: Reddish brown
  • Shape: Elongated oval body with a distinctive long “snout”
  • Found in: Common over the whole of the United States

General Overview
The wheat weevil is also known as the “grain weevil.” As it’s name suggests, this insect is a threat to dried goods and grains. It is considered an economic pest due to it’s destructive nature. Their size varies in response to the grains that they feed upon, which is due to the weevil’s habit of laying it’s eggs within the grains it targets. The larval and pupal stage of the weevil occurs entirely within the kernel of grain that their egg has been laid in. Wheat weevils are known to “play possum” when threatened and are incapable of flight.
Signs of Infestation
Signs of an infestation of wheat weevils are often not obvious and it is difficult to spot an infestation. The best way for a commercial farmer to tell if they have these weevils is a intensive survey  of the grains that they sell, which may prove extremely difficult if it is a smaller form of grain such as wheat as the weevils themselves will be proportionately sized. It is, however, easier to tell if you have a infestation by weight, as an infestation of wheat weevils will decrease the weight of the grain as they consume it.
In the home, wheat weevils are detected by examination of the dried goods of the home, though they are not as common there since the female requires whole grains within which to lay it’s egg. If you suspect that you may have a weevil infestation, a good way to test grain is to see if it floats in water.
The wheat weevil, while it does have vestigial wings, is flightless and therefore prefers stored grains over those in the field. And due to the vast size of many commercial granaries a weevil infestation can also be protected from both weather and temperature extremes by the very food they live in. Unfortunately this means that is is very difficult to get rid of an infestation once it has taken hold without completely eradicating the grain store. Wheat weevil can enter the home through already infested grains.
Eating habits
The wheat weevil feeds on many different varieties of grain, including wheat, oats, rye, barley, rice and corn. The wheat weevil female chews a hole in a grain kernel, lays their egg and then seal the opening with a secretion. Then when the egg hatches the larvae eats the interior of the seed, continuing to remain inside the kernel until they emerge as adults. When in the household, the wheat weevil can be found in grains like oats, rice and barley where their life cycle is unaffected by their surroundings.
Treatment and Prevention
The best way to keep your home from exposure to an infestation of wheat weevils to to make sure that your grains are stored in tightly sealed containers. It is recommended that you purchase your grain in small quantities and then keep it in fortified containers or even in the freezer. If you find that you have weevils, the only course of action to make sure that you are rid of the infestation is to get rid of all infested grains.

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