Any disease-causing organism (fungus, bacterium, virus, nematode) that infects plants, causing disease and damage.
Pathogens are disease-causing microorganisms. Fungal pathogens cause most plant diseases (powdery mildew, blights, rots). Bacteria cause some serious diseases (fire blight, bacterial wilt). Viruses cause incurable diseases. Nematodes (microscopic worms) damage roots. Understanding pathogen types helps choose prevention and management.
Understanding pathogens helps you prevent diseases. Different pathogens need different management approaches.