Plant pathogens, Microorganisms belonging to the same taxonomic class, including bacteria, viruses, fungi, protozoa and nematodes, including disease-causing pathogens in humans and animals, are, with a few minor exceptions. Around 100 types of pathogens appear to be targeting each species of plants. Plant pathogens and bacteria live most of the time in their plant hosts and the remainder of the time in the soil. The other pathogens live only in their plant hosts. Pathogenic plants cause disease in plants and cause food losses and other essential articles. The losses can be light or very heavy, sometimes killing all the plants and causing malnutrition, malnutrition and famine, while in other cases they cause the extinction of whole plant species.