DISEASES OF GINGELLY OR SESAME – Agricultural study materials

1. LEAF BLIGHT – Alternaria sesami

 Symptoms

Small circular, reddish brown spots [1-8 mm] appear on leaves which enlarge later with concentric rings. Lesions may coalesce to form large necrotic areas and defoliation usually results. In severe blighting dark brown lesions can be seen on petiole, stem and capsules. Infection of capsules results in pre mature splitting with shriveled and poorly mature seeds.

Mode of spread and survival 

Wind borne conidia spread the disease and the pathogen survives in the infested seeds

Epidemiology 

Low temperature (20 to 25⁰ C), high relative humidity and cloudy weather favour the disease development

Management

• Seed treatment with thiram or carbendazim at 2 g/kg of seed
• Spray mancozeb @ 1 kg/ha

2. LEAF SPOT – Cercospora sesami

  Symptoms

Dark brown, round to irregular spots [5-15 mm] appear on both the surface of leaves. The linear spots occurring on pods causes drying and pre mature shedding

Mode of spread 

The disease spreads through wind borne conidia

Survival 

The pathogen survives as externally and internally seed borne inoculum

Epidemiology 

Cloudy weather encourage the disease development

Management

• Seed treatment with thiram or carbendazim at 2 g/kg of seed
• Spray mancozeb @ 1 kg/ha

3. LEAF AND STEM BLIGHT – Phytophthora parasitica var sesami

Symptoms

Black coloured lesions appear on the stem near the soil and may girdle the stem, resulting in the death of the plant. Infected capsules are poorly developed with shriveled seeds.

Mode of spread and survival 

The pathogen spreads through wind borne sporangia and survives in the infested seed and soil

Epidemiology 

Prolonged rainfall and low temperature help in the disease development

Management

• Field sanitation
• Seed treatment with captan or thiram at 2 g/kg of seed
• Avoid continuous cropping of sesame in the same field
• Grow disease free cultures like ES 25, 105, 124, 156 and 190 

4. ROOT ROT/CHARCOAL ROT – Macrophomina phaseolina

    Charcoal rot of sesame is very destructive and present in all the sesame growing areas   

Symptoms

The pathogen attacks the stem at the collar region. The symptoms include yellowing of lower leaves (collar region), drooping and defoliation. Inside the affected stem and roots numerous black sclerotia can be seen and the diseased plants can be pulled out very easily from the soil. Infected pods, open pre maturely and immature seeds become shriveled and black in colour

Mode of spread and Survival

The pathogen is soil borne and survives as soil borne sclerotia

Epidemiology 

Prolonged drought followed by rain encourage the disease development

Management

• Seed treatment with captan or thiram or  T.viride at 4 g/kg of seed
• Application of FYM or green leaf manure @ 10 ton/ha or neem cake @ 250 kg/ha
• Grow disease tolerant varieties like C 50, Gwalior 5, RT 1, 157 and Si 58.

5. WILT – Fusarium oxysporium f.sp.sesami

Symptoms

The disease is characterized by yellowing, drooping and withering of leaves. The infected portions of root and stem show long, dark black streaks due to vascular necrosis

Mode of spread 

Rain splash and irrigation water [conidia] spreads the disease

Survival 

The pathogen survives in soil and infested plant debris

Epidemiology 

High soil temperature favour the disease

Management

• Seed treatment with captan or thiram or  T.viride at 4 g/kg of seed
• Application of FYM or green leaf manure @ 10 ton/ha or neem cake @ 250 kg/ha
• Spot drenching with 0.1 % carbendazim in the root region

6. POWDERY MILDEW – Erisiphe cichoracearum

Symptoms

Small, white powdery growth appears on the upper surface of leaves and in severe cases, the spots coalesce and the entire leaf surface becomes covered with powdery coating. The infection may be seen on the flowers and young capsules, leading to premature shedding.

Mode of spread 

Spreads through wind borne conidia

Survival

The pathogen survives in the infected plant debris

Epidemiology 

Dry humid weather and low RH favour the disease. 

Management

• Remove and destroy the infected plant debris
• Application of sulphur dust @ 25 kg/ha or spraying wettable sulphur @ 2.5 kg/ha
• Grow resistant cultivars like Si 44, 68, 71, 250, 1157, 1167, EC 20804, 20810 and 20835.

7. BACTERIAL BLIGHT – Xanthomonas campestris pv.sesami

Symptoms

Small, water – soaked, translucent circular spots appear on lower surface of leaves and in severe cases, the spots coalesce and form irregular brown patches giving a blighted appearance.

Mode of spread 

The bacterium spreads through wind splashed rains 

Survival

Survives in the seed and infected plant debris

Epidemiology 

Warm temperature and frequent rain encourage the disease development

Management

• Field sanitation
• Hot water treatment of seeds at 52⁰ C for 10 minutes
• Spray streptocycline at 400 ppm thrice 25 days after spraying
• Grow resistant culture T.58

8. BACTERIAL LEAF SPOT – Pseudomonas sesami

Symptoms

Water soaked yellow spots appear on the upper surface of the leaves. The colour of spot may be dark brown with shiny ooze of bacterial masses

Mode of spread 

    The bacterium spreads through wind splashed rains 

Survival

    Survives in the seed and infected plant debris

Epidemiology 

    Warm temperature and frequent rain encourage the disease development 

Management

• Field sanitation
• Hot water treatment of seeds at 52⁰ C for 10 minutes
• Spray streptocycline at 400 ppm thrice 25 days after spraying

9. LEAF CURL – Nicotiana virus

Symptoms

The characteristic symptoms are severe downward curling of the leaves and marked thickening of the veins on the lower surface of the leaves. In severe cases the plants remain stunted and bear very few flowers and fruits

Vector

    The disease is transmitted by white fly – Bemisia tabaci

Management

• Spray with methyl demeton @ 0.025 % or demethoate @ 0.03 % to control vectors
• Grow resistant variety Entebbe ex Uganda and cultures like T 15/1-1, kanpur local

10. PHYLLODY – Phytoplasma [MLO]

Symptoms

The plants bear cluster of leaves and malformed flowers at the tip. Infected floral parts are transformed in to green leafy structures, which grow profusely. The flower is rendered sterile. The plant is stunted with reduced internodes and abnormal branching, gives a bushy appearance. The most characteristic symptom of the disease is transformation of flower parts in to green leaf-like structure. In the phylloid flowers 5 stamens are found were as only 4 stamens are found in normal flowers  

Vector

The disease is best transmitted by Leaf hopper – Orisius albicinctus 

Management

• Rogue out the infected plants periodically and remove all the reservoir and weed hosts.
• Spray dimethoate or carbaryl @ 500 ml/ha to control the vectors.
• Swetha Til [JCS. 96] is tolerant variety to this disease.