DISEASES OF SUNFLOWER – Agricultural study materials

Agri Diseases

DISEASESCAUSAL ORGANISM
RustPuccinia helianthi
Leaf blightAlternaria helianthi
Root rot or charcoal rotMacrophomina phaseolina
Head rotRhizopus nigricans

1. RUST – Puccinia helianthi

Symptoms

Small, reddish brown pustules (uredia) covered with rusty dust appear on the lower surface of bottom leaves. In severe infection, numerous pustules appear on leaves leading to yellowing and drying of leaves. The black coloured telia are also seen among uredia on the lower surface. Pycnial and aecial stages occur on volunteer plants.

Mode of spread 

The disease spreads through wind borne uredospores

Survival

The pathogen is an autoecious rust and survives in the volunteer sunflower plants and infected plant debris

Epidemiology 

Rainy weather and cool winter encourage the disease development

Management

  • Remove the volunteer sunflower plants
  • Field sanitation
  • Spray mancozeb @ 1 kg/ha
  • Grow resistant genotypes  EC 32361, 82819, MSFH 3, 9, 12 and BSH 1.

2. LEAF BLIGHT – Alternaria helianthi


Symptoms

Dark brown to black, circular to oval spots surrounded by a chlorotic zone with grey white necrotic centre appear. In severe cases, spots enlarge in size, coalesce and cause blighting of leaves and defoliation occurs.

Mode of spread and survival

The pathogen spreads through wind borne conidia and survives in the seeds

Epidemiology 

low temperature and high relative humidity favour the disease

Management

  • Remove and destroy the infected plant materials
  • Early sowing (June sowing)
  • Seed treatment with thiram or carbendazim at 2 g/kg of seed
  • Spray mancozeb @ 1 kg/ha
  • Grow resistant genotypes like EC 126184, 132846, 132847 and TNAU Suf 5.


3. ROOT ROT/CHARCOAL ROT – Macrophomina phaseolina

Symptoms

Affected seedlings show brown or ashy black discolouration at the collar region. The infected plants show drooping of leaves and death occurs in patches. The bark of the lower stem and roots shred and associated with a large number of sclerotia

Mode of spread

Primary infection takes place from the inoculum in soil and secondary infection takes place through air-borne spores

Survival

The pathogen survives as sclerotia in soil, irrigation water and implements

Epidemiology 

Dry weather favour the disease

Management  

  • Seed treatment with thiram or captan or T.viride @ 4 g/kg of seed
  • Soil drench with carbendazim @ 0.1 %

4. HEAD ROT – Rhizopus nigricans

Symptoms

Affected heads shows water-soaked lesions on the lower surface and later turns to brown. The affected seeds are converted in to a black powdery mass.

Mode of spread 

    Spreads through wind borne sporangiospores

Survival

    Survives in the infected plant debris

Epidemiology 

    Prolonged rain at flowering stage encourage the disease

Management  

  • Seed treatment with captan or thiram at 4 g/kg of seed
  • Spray the head with mancozeb @ 1 kg/ha

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