..Types
Types
Root and butt rots
These are wood-decay diseases, and overlap with stem decays. Most are caused by Basidiomycota. They may get in through wounds in the lower part of the tree or penetrate roots directly. They involve the roots and in some cases the butt also.
They may be found killing cambial tissues or growing in the inner wood:
- For cases where the fungus kills cambium at the root collar, the tree will die when the root collar is girdled (killed all the way round). This is quickly lethal.
- In other cases, the fungus decays the inner wood at the base of the stem (heartwood). This is called butt rot. A tree can live with butt rot for many years, just as it can with stem decay in the main stem. Very often the tree dies because it is uprooted or snapped (physical failure) rather than direct mortality from killing tissues.
Cortical root rots
The cortex is the succulent outer tissue of young roots.
As the root becomes woody, the cortex gets squashed, and instead we have cambium
and phloem
(inner bark), which is also succulent and rich in nutrients. Many of the
fungi that can attack the cortex of young roots can move into the cambium
and phloem of woody roots.
This group overlaps with nursery diseases, many of which are cortical root rots. Here we just consider those that are known to be important in big trees.
Most of the well-known pathogens
of mature trees in this group are water molds (Oomycota).
Vascular wilts
A vascular wilt is a disease in which the pathogen moves in the active xylem, disrupting the flow of xylem sap, causing wilting and other drought-like symptoms.
These could be better grouped with the other vascular wilts that we'll learn about later, but some infect through the roots and can spread from tree to tree by mycelial growth the way many root diseases can, so we think of them more as root diseases. They do not cause root "rot."
Most are caused by Ascomycota or Deutermycota.
We'll go through that with each fungus, as it varies slightly. But one thing you should keep clearly in mind: in addition to airborne dispersal by spores (which most of them can do), they can usually grow as mycelium from one tree to another, across root contacts or grafts. So there are two kinds of inoculum: airborne (spores) and soilborne (infested stumps and root systems).
Information provided by: http://www.forestpathology.org