Fungi (plant pathogen)
Fungi are small, spore-bearing organisms that do not possess chlorophyll. There are more than 100,000 known species of fungi. Most fungi have a positive impact on agriculture and are essential as decomposers of dead, organic material. There are also various fungi that can help the plant absorb nutrients and increase its resistance to diseases. But more than 10,000 fungi are known to cause plant diseases that can cause considerable crop damage under favorable conditions.
How do you recognize them?
A fungus usually consists of threads (hyphae) that branch out and form spore-bearing structures. These structures are characteristic of the type of fungus and range from a dull shape to particularly elaborate and colorful. Often, the fungus is difficult to see with the naked eye, as it may be latent in a plant for some time without giving visible symptoms. Microscopic examination can give a result if spores are produced abundantly. With some fungi, however, this is more difficult and molecular examination is required to properly identify the pathogen.
What symptoms do they cause?
Fungi can enter through natural openings (stomata) or dissolve the cell wall with the help of enzymes and infect the plant. A number of vascular fungi produce wilting symptoms. In addition, fungi may be the causative agents of root rot, stem base infestation, necrotic spots on leaves, or the death of plant parts.
How do they spread?
The spread of fungi is possible because fungal threads or spores enter the greenhouse through air, contaminated water or plant material. Some pathogenic fungi are highly dependent on their host and only multiply if the host remains alive. Other fungi are able to survive in the soil for long periods through certain survival spores (sclerotia) and strike again when conditions are again favorable for infecting a plant.