| DISEASES | CAUSAL ORGANISM |
| Seedling blight | Phytophthora parasitica |
| Rust | Melampsora ricini |
| Leaf blight | Alternaria ricini |
| Brown leaf spot | Cercospora ricinicola |
| Bacterial leaf blight | Xanthomonas campestris pv. ricini |
1. SEDLING BLIGHT – Phytophthora parasitica
Symptoms
The disease appears as circular, dull green patch on both the surface of the cotyledonary leaves. Later it spreads and cause rotting. Infected stem show black discolouration and severe defoliation
Mode of spread and survival
The pathogen spreads through wind borne sporangia and survives in seeds and as oospores in soil
Epidemiology
Cool and moist conditions, continuous rains encourage the disease development.
Management
- Diseased plants should be removed and burnt
- Avoid low-lying and ill drained fields for sowing
- Seed treatment with thiram @ 3 g/kg of seed
2. RUST – Melampsora ricini
Symptoms
Minute, orange-yellow coloured, raised pustules appear with powdery masses on the lower surface of the leaves. Pustules are grouped in concentric rings and drying of leaves results. The fungus produces only uredospores in caster plant
Mode of spread and survival
The pathogen spreads through air borne uredospores and survives in the self-sown caster crop
Epidemiology
Cloudy weather favour the disease
Management
- Rogue out the self sown caster crop and other weed host
- Sulphur dusting @ 25 kg/ha or spraying mancozeb @ 1 kg/ha
3. LEAF BLIGHT – Alternaria ricini
Symptoms
In leaves, irregular brown spots with concentric rings, variable in size appear which are usually surrounded by yellow halos. In severe cases, the stem, capsules, and inflorescence also show dark brown lesions and premature defoliation occurs.
Mode of spread
Spreads through air borne conidia
Survival
The pathogen is externally and internally seed borne
Epidemiology
High relative humidity, low temperature with moist condition favour the disease
Management
- Seed treatment with thiram or carbendazim @ 2 g/kg of seed
- Three spray of mancozeb at 1 kg/ha at 15-90 days intervals
4. BROWN LEAF SPOT – Cercospora ricinicola
Symptoms
Minute brown spots surrounded by a pale yellow halo. Infected leaf tissue in the spot may break off leaving a shot hole symptom
Mode of spread
Spreads through air borne conidia
Survival
The pathogen survives as dormant mycelium in plant debris
Epidemiology
Low temperature and cloudy weather encourage the disease
Management
- Remove the infected plant debris and destroy
- Spraying with Bordeaux mixture @ 1 % or COC @ 0.25 %
5. BACTERIAL LEAF BLIGHT – Xanthomonas campestris pv. ricini
Symptoms
Water soaked lesions appear, which later become brown/black and angular to circular in shape. Later the affected leaves become brittle, dry up, drop prematurely and defoliate.
Mode of spread and survival
The pathogen spreads through rain splash and survives in the infested seeds
Epidemiology
Poor drainage and heavy rain encourage the disease development
Management
- Use disease free seeds
- Surface irrigation only during periods of low rainfall may serve to reduce losses.
