After successful completion of 13 Units in this Lesson, you have learned to: List the fungal diseases damaging the groundnut leaves. Describe the symptoms

After successful completion of 13 Units in this Lesson, you have learned to:

• List the fungal diseases damaging the groundnut leaves.

• Describe the symptoms of each of these leaf diseases caused by fungi in groundnut.

• Employ management practices, if needed, to control these leaf diseases in groundnut.

Virtual Academy for the Semi Arid Tropics

Lesson 1: Leaf Diseases

Course on Diseases of Groundnut

Module III: Diseases Caused by Fungi

Please note that most of these leaf diseases are not economically important as these diseases may not cause much damage to the crop. Hence, no management practice is normally required for these foliar diseases.

The leaf diseases that are economically important are dealt in Module II of this Course.





The 13 Units in this Lesson are:

Unit 1: Web Blotch Unit 8: Zonate Leaf SpotUnit 2: Scab Unit 9: Sclerotium Leaf SpotUnit 3: Alternaria Leaf Spot Unit 10: Pepper SpotUnit 4: Phyllosticta Leaf Spot Unit 11: AnthracnoseUnit 5: Powdery Mildew Unit 12: Alternaria Leaf BlightUnit 6: Cercospora Leaf Blight Unit 13: Pestalotiopsis LeafUnit 7: Myrothecium Leaf Blight Blight

Click “Unit” to select the Unit





Symptoms

Scattered tan colored specks or streaks appear on the upper surfaces of the lower leaves.

The discolored areas expand, forming large, nearly circular, purplish brown to dark brown blotches with inconspicuous margins (Fig.).

Blotches often coalesce and cover the entire leaflet.

Unit 1: Web Blotch





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The fungus also invades petioles, stipules, and stems.

Severe disease attack leads to premature defoliation.

Unit 1: Web Blotch





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Symptoms

Numerous round to irregular lesions appear on both surfaces of leaflets.

The lesions on upper leaflet surfaces are light tan with sunken centers and raised margins.

Lesions are frequently covered with continuous velvet-like layers of grayish olive green fruiting bodies.

Unit 2: Scab





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Symptoms

The lesions on petioles and branches may develop into cankerous scabs, giving the plants a burnt appearance (Fig.).

Lesions cover nearly all of the plant, including pegs.

In advanced stages of disease development plants are stunted.

Unit 2: Scab





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Symptoms

Small, chlorotic, water soaked lesions appear on both surfaces of the leaflets.

These lesions enlarge, become irregular in shape, and are brown with darker brown margins; the central portions later become pale, dry rapidly, and disintegrate.

Unit 3: Alternaria Leaf Spot





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Symptoms

Veins and vein-lets adjacent to the lesions die.

Affected leaflets are chlorotic (Fig.).

In severe attacks they age prematurely age and dry.

Adjacent lesions join together, giving the leaf a ragged and blighted appearance.

Unit 3: Alternaria Leaf Spot





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Symptoms

Infection starts in damaged and dead tissue and subsequently spreads into the living green areas of the leaflets.

Lesions are circular to irregular and are light tan in color surrounded by a reddish-brown border (Fig.).

Unit 4: Phyllosticta Leaf Spot





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Unit 5: Powdery Mildew

Symptoms

Large whitish spots cover the upper surfaces of leaflets.

These spots are covered with fungal growth that gives them a powdery white appearance.

The centers of the spots later become brown and necrotic.





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Symptoms

Small necrotic lesions appear on leaflets.

These lesions enlarge and become irregular or angular shaped light brown spots (Fig.).

When long periods of leaf wetness occur, the spots join together leading to drying of leaves and defoliation.

Unit 6: Cercospora Leaf Spot





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Symptoms

Round to irregular lesions with gray brown colored centers and brown margins surrounded by chlorotic halos occur on both surfaces of leaflets.

When lesions join together, give dried appearance on leaves (Fig.).

Unit 7: Myrothecium Leaf Blight





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Symptoms

Small lesions have a light brown center surrounded by a brown ring of dried tissue. Large lesions show a Zonate pattern on both surfaces of leaflets.

Unit 8: Zonate Leaf Spot





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Symptoms

Appear on mature plants as gray necrotic ring spots which may develop shot holes.

During long periods of leaf wetness the spots coalesce leading to a severe blight.

Unit 9: Sclerotium Leaf Spot





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Symptoms

Numerous minute, dark brown to black, and irregular to circular spots appear on lower leaves.

Such spots appear on both sides of the leaflet; but are more often found on upper surfaces.

Unit 10: Pepper Spot





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Symptoms

Leaf scorch, the most common symptom, frequently develops on the tips, and occasionally on the margins, of leaflets.

The wedge shaped lesions have a bright yellow zone along the periphery of their advancing margins. The drying tissue becomes dark brown and tends to break along the leaflet margins (Fig.).

Unit 10: Pepper Spot





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Symptoms

Wedge shaped lesions resembling pepper spot disease appear on the leaflet tips.

Lesions may also develop on the leaflet margins leading to marginal blight.

The periphery of the advancing margins of the lesion is surrounded by a bright yellow zone (Fig.).

Unit 11: Anthracnose





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Symptoms

Light to dark brown irregular spots appear towards the tips or margins of the leaves.

These rapidly enlarge and join together to form wedge shaped lesions (Fig.).

Unit 12: Alternaria Leaf Blight





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Symptoms

In the later stages of disease development, blighted areas become dark brown and tend to break.

The scorch symptoms resemble those caused by Pepper Spot and Anthracnose. It is often difficult to distinguish between these diseases in the field.

Unit 12: Alternaria Leaf Blight





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Symptoms

Dark brown circular spots surrounded by faint yellow haloes appear on infected leaves.

These spots enlarge and join together to dry up the leaflets, especially on the margins (Fig.).

Unit 13: Pestalotiopsis Leaf Blight





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With this, the Lesson 1 on Leaf Diseases caused by fungi in groundnut concludes.

Next, Lesson 2 is about Seed and Seedling Diseases caused by fungi in groundnut.

Select Lesson 2 from Module III contents




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Documents

After successful completion of 13 Units in this Lesson, you have learned to: List the fungal diseases damaging the groundnut leaves. Describe the symptoms