The grain weevil is part of the true weevils family. It is 3 to 5 mm long and plain red-brown to black-brown in colour. It cannot fly, lives predominantly in grain stores and feeds off all types of grains there. When it comes to laying eggs, the female chews a hole in a grain, lays the egg inside and then seals the opening with a secretion. The entire development cycle from egg to larva to pupa takes place out of sight in the grain. The grain is nearly entirely devoured in the process.
The creatures are relatively tolerant to cold temperatures and can therefore hibernate in unheated stores.
Grain weevils are one of the most common primary pests for grains globally – in other words, they can infest entire cereal grains, whereas lots of other types of beetles are reliant on grains which are broken in part.
In countries with a temperate climate, the grain weevil is the main pest in grains in storage. Affected grains warm up and become stale, and secondary pests, such as bacteria, fungi and mites settle.
In addition to the feeding damage caused by the larvae, the extreme rate of reproduction is the main reason for losses, as the affected goods can no longer be sold and are therefore wasted.