Diseases of Cumbu, Pearl, Millet, Bajra – Agricultural study materials

Agri Diseases

DISEASES OF CUMBU/PEARL MILLET/BAJRA

DISEASESCAUSAL ORGANISM
Downy mildew or green earSclerospora graminicola
Ergot or sugary diseaseClaviceps fusiformis
SmutTolyposporium penicillariae
RustPuccinia penniseti


1. DOWNY MILDEW/GREEN EAR – Sclerospora graminicola



Symptoms

The first symptom appears in seedlings at 3-4 leaf stage. Affected leaves show patches of light green to light yellow colour on the upper surface of leaves and the lower surface shows white downy growth of the fungus. The affected ear is transformed in to green leafy structure hence the name “green ear” disease. Mostly the entire ear is transformed in to leafy structures, but at times a part of the ear also affected and the other parts produce normal grains. As the disease advance, the green leafy structures become brown and dry.

Mode of spread and Survival

The secondary spread of the pathogen is through sporangia which are spread by rain splash/wind and irrigation water. The pathogen is soil borne and the oospores in soil and infected seeds survive for 10 years.

Epidemiology

A temperature of 15-25oC, High humidity and rainy season favour the disease development. The disease is severe when the crop is grown in October – November and negligible when sown in March – April.

Management

  • Summer deep ploughing and crop rotation
  • Seed treatment with metalaxyl at 4g/kg of seed
  • Spray mancozeb 1.25 kg/ha or metalaxyl + mancozeb @ 2kg/ha at 20 DAS
  • Grow resistant varieties like CO-6, 7, WCC 75, X 5.



2. ERGOT/SUGARY DISEASE – Claviceps fusiformis

Symptoms 

The disease occurs only at the time of flowering. Small droplets of light, honey-coloured dew like substances exude from infected spikelets. These honey dew contains millions of conidia. Finally, the infected ovary turns in to long dark brown ‘’sclorotia’’.

Mode of spread and Survival

The honey dew attracts insects and ants which help in secondary spreading of the disease. Also the disease is spread by rains. The pathogen survives as Sclerotia in soil which is viable for 6-8 months.

Epidemiology

High relative humidity, Cloudy weather and intermittent raining for 5-6 days during flowering stage encourage the disease.

Management

  • Adjust the sowing date so that flowering doesn’t coincide with rains
  • Immerse the seeds in 10 % salt solution and remove the floating sclerotia
  • Spray with mancozeb 1.25 kg/ha or zineb or ziram @ 1 kg/ha

3. SMUT – Tolyposporium penicillariae


Symptoms

The pathogen infects the florets and transforms them into large sacs containing black powder of smut spores. A few grains sporadically distributed on the ear, may be replaced as sori. When the sori mature, they become dark brown and easily broken and release millions of black smut spore balls.

Mode of spread and survival  

The pathogen is soil borne and survives as spore balls in soil. These spore balls germinate to give rise sporidia which are carried by wind and effects the secondary infection. 

Epidemiology

    High humidity and successive cropping of pearl millet favours the disease development.

Management

  • Removal and destruction of affected ear head
  • Deep summer ploughing and crop rotation

4. RUST – Puccinia penniseti

 Symptoms

The disease first appears on the older leaves as pustules containing reddish brown uredospores. Later, dark brown teliospores are produced. The rust pustules can appear in groups on both surfaces of leaves, leaf sheath and stem. 

Life cycle

Uredial and telial stages are completed on cumbu and Aecial and pycnidial stages are completed on brinjal (Alternate host)

Mode of spread and survival  

The pathogen spreads through air borne uredospores or aeciospores from alternate host. 

Epidemiology

    Rainy weather and low temperature encourage the disease development.

Management

  • Spray with captafol 1 kg/ha or mancozeb 1.25 kg/ha
  • Grow resistant varieties like IP 537-B, P – 2890, 1577, 1581 and 2880

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