Diseases of Fruit Plantation Medicinal and Aromatic Crops

Armillariella root rot

Causal organism: Armillariella mellea.

• It occurs in all the temperate region but limited to tropics in Africa and Asia where it is more predominant in mountain areas, but it also occurs in lowland areas in Central and West Africa.
• Usually the disease becomes apparent after it has severely damaged the root system of bushes as the foliage begins to wilt, turn chlorotic and falls, 'Death of the whole plant then follows.'
• As the parasite spreads up to the roots and reaches the collar region, of the tissue beneath the bark often cracks.
• Sheets of creamy coloured mycelium appear beneath the bark accompanied by flattened brown rhizomorphs.
• Rhizomorphs are also found on outside of roots where they often grow epiphytotically in advance of infection.
• The characteristic sporophores are usually produced on the collar region of the host in advanced stage of the disease? They occur in clumps, are pale brown and mushroom -shaped.
• Old tree stumps large root pieces or other woody material that has been colonized by the fungus act as the main sources from which the pathogen invades tea bushes or other perennial crops. Rhizomorphs can grow through the soil to reach potential hosts Basidiospores from the sporophore are able to initiate saprophytic growth which can colonise wood.