Powdery mildew

Powdery Mildew
    Causal organism: Erysiphe cinnamomi
    Symptoms
    • Whitish grey colour powdery growth on upper surface of leaf, powdery growth enlarges.
    • In severe condition, it may move to lower surface.
    • Leaf slowly cupping, later leaf dropping takes place.
    • Powdery growth on stem. Powdery growth consists of oidia and mycelia strands.
    • The stem and petioles in later stages are also affected and are covered with a dirty white mycelia and oidia.
    • With the advancement of the disease, the leaf lamina develops complete or partial chlorosis and the affected leaves eventually dry up
    Etiology
    • Septate, ectophytic mycelia with sub epidermal haustoria.
    • Asexual spores are barrel shaped conidia bearing in chains.
    • Sexual stage is Ascospores in ascus and the fruiting body is cleistothecium
    • PRIMARY SOURCE OF INOCULUM: Dormant mycelia, cleistothecium present in crop debris.
    • SECONDARY SOURCE OF INOCULUM: Barrel shaped conidia.(Oidia)
    • SPREAD: Air borne
    Life cycle

    Epidemiology
    • The optimum Temperature for the spread of the disease is 28 to 300
    • Requires Warm weather.
    • This disease is more at the time of September- October months
    • Relative humidity required is 80 to 85 %
    Management
    • Remove affected plant parts and destroy.
    • At early infection stage spray with wettable sulphur -0.3% followed by, spraying with carbendazim -0.1%t, calixin -0.15%.
    • Crop rotation with non-host crop.
    • Low nitrogen and increased K application reduces the incidence of disease..

Last modified: Friday, 22 June 2012, 1:53 PM