Pests come to us in steady streams of imports from southern countries. The pests exist in all links of the distribution path which rarely makes it possible to trace the source of the original infestation. It is difficult to determine responsibility unless the pests are detected in the imported goods before they reach the country that imports the goods.
The largest quantities of goods are transported by sea. When ships call into British or German ports the shiploads are thoroughly tested for food pests. In Nordic countries, this control is non-existing. It is also doubtful that such controls have any significant effects. Species imported in large amounts is in fact still quite rare as food pests in the cold Northern Europe. This applies to both countries that have import controls and countries which do not. It is assumed that most of the imported food pests die shortly after arrival either because it is too cold or because they live in the goods and possibly are eaten with them.
It is possible that a fraction of imported pests are lucky enough to be placed in a warm environment which allows them to establish themselves in this new environment. It is these imported pests alongside with pests from local nature that makes up our food pests.