Question

Annosus Root-rot diseaase is caused by a wood decay fungus known as

• A. Fomes annosus
• B. Annosus foam
• C. Ennomos subsignarius
• D. Archips sp.

Hint:

In forestry, the species name annosus directly matches the common name of the disease, Annosus root rot.
This makes it easy to identify Fomes annosus (or Heterobasidion annosum) as the causative pathogen.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Root rot diseases can cause significant damage in forestry, leading to decay, windthrow, and mortality in conifer stands.
Managing these diseases requires identifying the specific wood-decay fungus responsible.

Step 2: Detailed Explanation:
Annosus root rot (also known as Heterobasidion root disease) is a destructive fungal disease affecting coniferous forests worldwide, particularly pines, spruces, and firs.
The disease is caused by the basidiomycete wood-decay fungus historically called Fomes annosus (now classified as Heterobasidion annosum).
The fungus primarily spreads by dispersing airborne basidiospores, which colonize the freshly cut surfaces of tree stumps.
Once established, the mycelium grows down through the stump's root system and spreads to adjacent healthy trees through root contact or root grafts.
As the fungus colonizes the root system, it degrades lignin and cellulose, causing a white stringy rot that weakens the roots and base of the tree.
This decay makes the trees unstable and prone to windthrow.
Let us evaluate the other options:
- "Annosus foam" is a distractor.
- Ennomos subsignarius is an insect (the elm spanworm), which is a defoliator, not a fungus.
- Archips is a genus of leafroller moths, not a plant-pathogenic fungus.
Therefore, the disease is caused by the fungus Fomes annosus.

Step 3: Final Answer:
Annosus root rot in conifer forests is caused by the wood-decay fungus Fomes annosus.