Pests are simply unwanted animals and insects. They can be unwanted in general or under special conditions, but no rational reasons are really needed for not wanting them.
Some kinds of pests infest living plants and animals. Others, the decomposers, only occur when an animal or vegetable product is created. The latter group is the food pests. These two different kinds of pests practically do not share any of the same species.
Food pests are the insects and rodents that infest stored goods which are either for sowing or for food for either people or domestic animals both directly and processed.