Such plants may contain and transfer vermins and plant diseases which may be harmful to Polish plantations and ecosystems (especially for the tree stands), even if the plants themselves do not show any signs of being infected.
The requirement to hold a phytosanitary certificate may concern other goods imported to the European Union than plants. A detailed list of such goods is enclosed in the EU regulations, common for all member states. These regulations list the goods, which are to be phytosanitary inspected on the EU borders.
EU regulations also specify goods, the import of which is strictly forbidden due to a high risk of dissemination of vermin or plant diseases. Detailed information on the phytosanitary restrictions, both national and European Union ones, are to be found on the website of the European Commission and, in case of Poland, on the website of the Polish Main Inspectorate of Plant Health and Seed Inspection (Polish version only).
It should be taken into consideration that losses incurred by newly introduced fungi, bacteria, viruses and viroids, causing plant diseases, for which no natural defense mechanisms were created, may result in:
- direct losses in harvests (total destruction of plants or lowering of the harvest's quality);
- necessity to undertake additional activities in order to protect the plants (chemical and agrotechnical treatment), which raise the costs of production;
- limitations of export possibility of national plant products (plants destined for plantation, fresh fruits and vegetables, wood) to be exported to other countries, which are not affected by such vermins and pathogens.
Problems caused by new vermins and plant diseases in tree stands, aside from causing material losses, also endanger the existence of whole ecosystems.