DISEASES 1

DISEASES 1

1. LEAF BLIGHT:
The disease is widespread in its occurrence. In India, it has been reported from Punjab, Bangalore and Pune.

Symptoms: Different blight symptoms are produced by two different pathogens:
a) Cercospora jasminicola:
  • The symptoms appear as circular to irregular, reddish- brown spots with a darker border on both surfaces of leaf and on other aerial parts of the plant.
  • Severe infection leads to premature defoliation which has an adverse effect on flowering.
  • The pathogen also attacks the stem and branches.
b) Alternaria jasmini:
  • Symptoms appear as reddish brown circular spots (2-8 mm in dia.) on the upper surface of leaves which spread rapidly during rainy season.
  • In severe disease conditions, vegetative buds and young branches dry up.
Pathogen:
  • Cercospora jasminicola Muller &Chupp infects Jasminum officinale and Alternaria jasmini attacks J. auriculatum.
    • C. jasminicola produces conidiophores which are amphigenous, arising in groups on a dark brown, thick-walled stroma, simple, septate, pale to olivaceous brown and geniculate with hyaline and narrow tips.
    • However conidia are numerous, hyaline, multicelled with 9-13 transverse septa, 36-88 x 1.53-4.5µm, obclavate to cylindrical, straight to curved with obconically truncate base and subacute tip.
    • Conidia of A .jasmini are muriform, beaked, brown, smooth and in chains.
Disease cycle and epidemiology:
  • The spread of the disease is high during rainy season with slight high temperature and humidity regimes.
  • Disease cycle and epidemiology are explained in detail under tomato and okra diseases.
Management:
  • Collect and burn the infected plant debris.
  • With the initiation of the disease, spray the crop either with carbendazim (0.1%) or benomyl (0.1%) or mancozeb (0.25%), or copper oxychloride (0.3%) and repeat at fortnightly interval.

2. LEAF SPOT
Symptoms:
  • Irregular to circular distinct spots are produced which are light yellow with reddish brown margins on upper surface and light grey on the lower surface.
  • The leaf spots caused by Septoria aichisonia are identical to anthracnose and show numerous pycnidia.
Pathogen:
  • Septoria aichisonia Sydow.
  • The fungus forms simple pycnidia with thin walls. Conidia are filiform, hyaline and multiseptate.
Disease cycle and Epidemiology
  • Disease cycle and epidemiology are explained in detail under tomato diseases.
Management:
  • Spray the crop either with zineb (0.25%) or mancozeb (0.25%) and repeat at 10 to 14 days interval depending on the severity of the disease.

3. RUST
The disease is wide spread in India and has been reported from Himachal Pradesh, Jammu and Kashmir, Maharashtra, Uttar Pradesh, Madhya Pradesh, Bihar, karnatka and Rajasthan.

Symptoms:
  • The fungus attacks leaves, stem and inflorescences.
  • Leaves show the presence of orange coloured aecial cups on both sides, but predominantly on the lower surfaces (Plate-1a & b).
  • The fructification or sori are formed on the thickened portions.
  • The sori are initially yellow owing to their contents, the aeciospores later turn darker due to formation of teliospores.
  • The infected portion becomes hypertrophied, cankers develop at the affected portions especially on the stem and blisters or swellings are formed on the leaves.
  • The affected portion later thickened and gets puckered and flower buds do not open in severe conditions.

27.1

Pathogen:
  • Uromyces hobsoni Vize.
  • The pathogen produces aecia which are raised, scattered, orange-coloured, aecidioid while aeciospores are orange-yellow, thin-walled, 16.5-21 x12-18 µm in size.
  • The teleutospores are dark brown, one celled, mostly ovate, thick-walled, 35-45x20-30 µm in size and pedicel is hyaline or yellow in colour.
  • The spermogonial stage is not observed.
Disease cycle and epidemiology
  • The infection is more in winter and spring season.
Management:
  • Collect and destroy the infected plant debris.
  • With the initiation of the disease, spray the crop either with mancozeb (0.25%) or EBI fungicides like hexaconazole (0.1%) or difenoconazole (0.05%) and repeat at 10 days interval.

4. WILT
The disease is most prominent on J. sambac.

Symptoms:
  • The above ground symptoms include yellowing of lower leaves which gradually spread upwards and finally resulting in death of plants.
Pathogen:
  • The disease is caused by fungi Fusarium solani (Mart.) Sacc. and Sclerotium rolfsii Sacc.
  • Disease cycle and epidemiology are mentioned under Peas and Beans.
Management:
  • Follow long crop rotation.
  • Solarize the soil atleast 40 days prior to planting.
  • Drench the soil around the plant with carbendazim (0.1%).
Last modified: Monday, 12 March 2012, 6:15 AM