Infectious Disease
Fungus
Organism can be microscopic size to large structures such as mushrooms. Fungus is composed of threads which can penetrate the epidermis, or skin, of a plant or enter through natural openings or wounds. Fungal diseases can kill leaves, stems or roots specifically, or enter at one point and spread to other parts of a plant. Fungus spreads by spores, which are single cells that move on wind or water droplets, people, animals, insects, tools and some seeds. Some can live for many years in soil, and some are air borne until they land on a suitable host. They can also live for many years in a plant, causing little damage, or cause great destruction very quickly. Not all fungi are bad - yeast makes bread rise, vinegar is formed when fungi cause fruit to ferment, antibiotics are derived from fungi. Some fungi, called saprophytes, are responsible for the decomposition of dead plant material. An example is mushrooms, which live on dead tree roots underground, and grow on lawns when poplar trees are cut down.
Three conditions necessary for fungal growth:
- a suitable host
- a pathogen (disease-causing agent)
- a suitable environment.
An example would be a slice of damp bread (suitable host) on a warm kitchen counter (suitable environment). It becomes blue and furry much more quickly that a sandwich in a cold refrigerator (drier and colder).