classification; crops; forestry; hosts; identification parasites; plant pathology; symptoms; Belgium; Congo Democratic Republic; Benelux; Developed Countries; European Union Countries; OECD Countries; Western Europe; Europe; ACP Countries; Central Africa; Africa South of Sahara; Africa; Francophone Africa; Least Developed Countries Developing Countries; phytopathology; Zaire; Forests and Forest Trees (Biology and Ecology) (KK100); Pests; Pathogens and Biogenic Diseases of Plants (FF600) (Discontinued March 2000); Parasites; Vectors; Pathogens and Biogenic Diseases of Animals (LL820) (Discontinued March 2000)