DISEASES OF RAGI / FINGER MILLET – Agricultural study materials

Agri Diseases

DISEASESCAUSAL ORGANISM
BlastPyricularia grisea
Seedling blight / leaf blightHelmithosporium nodulosum
Wilt / foot rotSclerotium rolfsii
Downy mildew/Green ear/Crazy topSclerospora macrospora
Smut Melanopsichium eleusinis
Mottle streak Mottle streak virus

1. BLAST Pyricularia grisea

Symptoms 

The pathogen attacks the crop from seedling stage to the time of grain formation. Characteristic spindle-shaped spots with yellow margin and grayish green center can be seen. The fungus, when infects the stem causes blackening of the nodal region. When the neck region is affected the tissues weaken and the heads droop.

Mode of spread

The primary infection takes place through seed borne inoculum and secondary spread is through air borne conidia

Survival

The pathogen survives in infected plant debris and collateral hosts

Epidemiology

    High humidity and continuous drizzles favours the disease development

Management

  • Seed treatment with captan or thiram 4 g/kg of seed
  • Spray with Iprobenphos or edifenphos @ 500 ml/ha or carbendazim @ 250 g/ha
  • Grow resistant varieties like CO 10, 11, 12, 13,



2. SEEDLING BLIGHT OR LEAF BLIGHT – Helmithosporium nodulosum


Symptoms

Affected young leaves show minute, light brown oval spots. In mature plants oblong and dark brown spots are formed. The spots on the leaf sheath and culms are irregular. The infected spikes turn brown and are often over grown by the sooty growth of the fungus

Mode of spread and Survival

The pathogen spreads through infected seeds and air borne conidia and survives in the infected seeds and collateral host

Epidemiology

A temperature of 30-320 C, high Relative humidity (80-90 %) favour the disease development

Management

  • Removal of collateral host
  • Seed treatment with captan or thiram at 4 g/kg of seed
  • Spray with mancozeb @1.25 kg/ha



3. WILT OR FOOT ROT – Sclerotium rolfsii

Symptoms

The fungus attacks basal stem portion, leaf sheath and culm. The infected portion becomes soft and dark brown in colour. Later, small spherical, dark coloured sclerotia are formed in the affected areas.

Mode of spread

     The pathogen spreads through irrigation water and farm implements

 Survival  

The pathogen survives in the soil as soil borne sclerotia

Management

  • Crop rotation with non-host plant
  • Spot drenching with copper oxy chloride @ 0.25 %


4. DOWNY MILDEW / GREEN EAR / CRAZY TOP – Sclerospora macrospora




Symptoms

The infected plants produce shortened internodes and show bushy/ bunchy appearance. Finally the abnormal spikelet produced gives a brush-like appearance.

Mode of spread

The primary infection takes place from the oospores present in the soil and infested seeds. 

Survival 

The pathogen survives in the collateral hosts and infected seeds

Epidemiology

Cool weather favour the disease development

Management

  • Crop rotation
  • Roguing out the affected plants

5. SMUT – Melanopsichium eleusinis

Symptoms

The smut fungus attacks only a few grains in an ear head. The infected grains are scattered irregularly. These are converted in to enlarged globose sacs, greenish at first but later turn dirty black and 5 to 15 mm in diameter.     

Mode of spread and survival

The fungus spreads through air borne conidia and survives in the soil and infected spikelets

Epidemiology

Low temperature and high humidity favour the disease development

Management

  • Seed treatment with captan or thiram @ 4 g/kg of seed
  • Grow resistant varieties. 

6. MOTTLE STREAK AND STREAK VIRUS 



Symptoms

    The affected plants are stunted, pale green in colour. Chlorotic streaks are formed on the leaves. Early infection leads to reduction of tillers and grain formation.

Vector

    Leaf hopper – Cicadulina bipunctella, C. chinai transmit the disease

Management

  • Rogue out the infected plant
  • Spray methyl demeton or monocrotophos 500 ml/ha at 20 days interval. Grow disease tolerant varieties – AKP-2

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