Red rust of mango

Red rust of mango

    The algal disease of mango has been observed in India and else where. Its major distribution in India has been in Bihar, Karnataka, and U.P. the disease appeared in an epidemic form in the state orchards in Tarai in 1956. Reduction in photosynthetic activity and defoliation as a result of algal attack lower vitality of the host plant.
    Symptoms
    • The disease is characterized by initial green coloured patches, as and when disease advances the organism turns red rusty spots on the leaves and young twig.
    • The spots are initially circular, slightly elevated and later coanesce to form irregular spots.
    • The upper surfaces of the spot consist of numerous, unbranched filaments, which project through cuticle.
    • Some of the filaments represent sterile hairs while others the fertile ones.
    • Spores mature, fall off and leave cream to white velvet texture on the surface of leaf.
      Etiology
      Cephaleuros virescens (Kunze).
      • The algae after a period of vegetative growth develop its reproductive structure.
      • Certain cells become sporangia. They are of 2 types.
      • Those formed directly on the thallus are sessile and thick walled, 40-50micrometer in diameter with orange pigments.
      • They are formed singly on the vegetative filaments. Some are produced above the surface on special sporangiophores consisting of thick, rigid, septate hairs with a length of 50micrometer, swollen into a vesicle at the tip. Each vesicle carries 3-6 sporangia on curved pedicels.
      • When the sporangia are riped, the contents are converted in to zoospores and liberated through an opening in the wall.
      • The zoospores are orange in color, ovoid and swim actively by means of cilia.
      Epidemiology
      • The disease is more common on close plantation.
      • The zoospores cause initial infection.
      • High moist condition favours development of fruiting bodies of the algae.

    Management

    • It is controlled by spraying with Bordeaux mixture 1.2% or COC0.1% or limesulphur.

Last modified: Monday, 16 January 2012, 5:21 AM