| DISEASES | CAUSAL ORGANISM |
| Rust | Puccinia helianthi |
| Leaf blight | Alternaria helianthi |
| Root rot or charcoal rot | Macrophomina phaseolina |
| Head rot | Rhizopus 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
