Cladosporium colocasiae  Sawada,1916  

Cladosporiosis of taro

General

• A mushroom widely distributed in Asia, Southeast Asia and Oceania, it is now observed in all the taro production zones of the inter-tropical belt.
• Dénomination anglo-saxone : Brown leaf spot or ghost leaf spot 
• Leaf-only disease.
• Mainly present on water taro ( Colocasia esculenta ), more rarely on taro of the genus Alocassia , it does not seem to affect taro of the genus Xanthosoma .

• Susceptible botanical family(s)

• Production areas affected :

• Organs attacked

Symptoms

• Symptoms :
  • Olive green (fig. 1 and 2) to orange-brown (fig. 3) spots, with a rather diffuse outline, developing on the lower leaves. Circular to irregular, measuring 5 to 15 mm in diameter, they affect the inter-vein tissues of the limbus and converge in places ((fig. 4). Their center is downy at first, becomes necrotic and then takes on a grayish tint.
  • Fairly characteristic orange-brown color of the spots observed on the underside of the leaves.
  • Attacks mostly occur on older leaves, but during severe attacks young mature leaves may show symptoms of the disease.
  • Only the leaves are affected
    • Round, olive green spots, quite numerous on the upper side of the leaf.
    • The spots are orange-brown on the underside of the leaf blade.
    • They are less numerous because all the spots do not necessarily cross the leaf blade (fig. 6, 7 and 8).

• Signs : septate brown conidiophores bearing lighter conidia are visible with a binocular magnifying glass but more easily with a light microscope (fig. 9 and 10). The conidia are few in number and of various shapes, unicellular or presenting up to 3 partitions, isolated or in short chains, sometimes branched (fig. 11).
• Possible confusion : Neojohnstonia colocasiae (taro orange spot disease)
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