Cercospora leaf spot of chilli: frog-eye symptoms and control in chilli, cotton and pulses

Photo at the top: Cercospora leaf spot on a capsicum leaf: round spots with pale centres and dark rings, and the leaf turning yellow, Photo: David B. Langston, University of Georgia, CC BY 3.0 US

Quick answer

Cercospora leaf spot of chilli is a fungal disease caused by Cercospora capsici. It makes round spots with a grey or white centre and a dark brown edge, like a frog's eye. Badly spotted leaves turn yellow and fall early, so the plant bears less. Clean up crop waste, use seed from a healthy crop, and spray a fungicide labelled for chilli when the first spots appear.

How to identify Cercospora leaf spot of chilli

In Hindi it is called sarkospora patti dhabba (सर्कोस्पोरा पत्ती धब्बा). In Telugu it is sarkospora aaku macha tegulu (సెర్కోస్పోరా ఆకుమచ్చ తెగులు), the Cercospora leaf spot disease. It is also called frog-eye leaf spot, because of the look of the spot. Check the older leaves first, then the stems, leaf stalks and fruit.

• Young spot: a small, round, brown spot on the leaf.
• Grown spot: the centre turns light grey to white, and the edge stays dark brown. TNAU (Tamil Nadu Agricultural University) notes the spots can grow to 1 cm or more across.
• Hole in the centre: sometimes the dry grey centre falls out, leaving a small hole.
• Spots join: many spots run together, and the leaf turns yellow.
• Leaf fall: badly spotted leaves drop early. The plant loses its leaf cover and gives fewer and smaller fruits.
• Stem, leaf stalk and fruit: TNAU notes the spots here are longer and oval, with a grey or whitish centre and a dark border. In bad cases, the tips of the twigs dry from the top down (die-back), as the ICAR-NCIPM chilli IPM package notes.

Cercospora leaf spot symptoms vs look-alikes

• Alternaria leaf spot: brown spots that grow larger and show rings inside, like a target. The centre does not turn white. See our guide to Alternaria leaf spot and blight in cotton, chilli and other crops.
• Bacterial leaf spot: starts as small, wet-looking (water-soaked) spots that later turn brown with a yellow edge. They are slightly raised on the lower side of the leaf. Bacteria cause it, so a fungicide will not cure it. Read how to identify and prevent bacterial leaf spot in chilli and tomato.
• Anthracnose: mainly on the fruit. It makes sunken, dark spots on ripening fruit, often with black dots in rings, and causes die-back of twigs. See anthracnose of chilli: fruit rot and die-back control.
• Powdery mildew: a white powder on the lower side of the leaf and pale yellow patches above. No frog-eye spots. See our powdery mildew fungicide guide for chilli.

Life cycle and when it attacks

The fungus lives on in old infected chilli leaves and plant waste in the field. It can also come with seed, and it can live on chilli plants that come up on their own from last season (volunteer plants). The ICAR-NCIPM chilli IPM package lists all three as the first source of the disease.

The spots make spores (tiny seeds of the fungus). Wind and rain splash carry them to new leaves and new plants. Each new spot makes more spores. So in wet weather the disease moves fast, from the lower leaves up the plant and across the field.

Warm weather with high humidity, long wet spells and dew on the leaves helps it most. Crowded plants that stay wet for long also help it. In Telangana and Andhra Pradesh, chilli stays in the field for many months, from the rainy season into the cooler months. Watch closely after long rainy, cloudy or foggy spells.

Crops it attacks

"Cercospora" is a group of fungi. Each crop has its own species, and each one stays mostly on its own crop. The spots look much the same: a pale centre and a dark edge.

Chilli and capsicum: caused by Cercospora capsici. It can appear at any stage once the plant has many leaves, and it does most harm when leaves fall during flowering and fruiting. Fewer leaves mean less food for the fruits, and the fruits are also exposed to sun scald.

Cotton: caused by Cercospora gossypina. TNAU describes round or uneven greyish spots on the leaves, with dark brown or blackish borders on the older leaves. It is favoured by dense planting, high humidity, and cloudy weather with on-and-off rain followed by dry weather.

Pulses (black gram and green gram): mainly caused by Cercospora canescens. TNAU describes many small spots with a pale brown centre and a reddish brown edge. Similar spots form on the branches and pods. In humid weather, leaves spot heavily and fall at flowering and pod formation, which is the stage that sets the yield. The fungus is carried on seed and lives on plant waste in the soil.

In groundnut, two other Cercospora species cause tikka disease. That disease has its own guide: tikka disease of groundnut: early and late leaf spot.

When to spray

We could not find a fixed economic threshold (a count of spots at which spraying starts to pay) for Cercospora leaf spot in the ICAR-NCIPM chilli IPM package or on the TNAU Agritech Portal. Instead, TNAU advises spraying as the disease starts. For chilli it advises two sprays, 10 to 15 days apart. For cotton it advises a spray when the disease starts. For black gram it advises a spray when the disease starts and another 10 days later.

So walk the field once a week. Turn over leaves on plants in different parts of the field, starting with the lower leaves. Spray as soon as you see the first frog-eye spots. Do not wait until leaves start falling. Check more often during long humid or rainy spells.

Cercospora leaf spot control without chemicals

• Clean up crop waste: after harvest, collect and destroy infected leaves, stems and plant waste. TNAU advises this for cotton, and the fungus survives the same way in chilli and pulses.
• Remove volunteer plants: pull out chilli plants that come up on their own from the last crop. They carry the fungus into the new crop.
• Healthy seed: collect seed only from healthy fruits and pods, or buy certified seed. The fungus can travel on seed in chilli and pulses.
• Crop rotation: do not grow the same crop in the same field season after season. The ICAR-NCIPM chilli IPM package advises rotation with crops that are not hosts.
• Spacing: follow the recommended spacing. Crowded plants stay wet longer, and TNAU lists dense planting as a condition that favours the cotton disease.
• Water: water at the base of the plant, not over the leaves, where you can. Drain extra water after heavy rain.
• Remove spotted leaves early: in a small plot, pick off the first spotted lower leaves and destroy them away from the field.
• Balanced fertiliser: feed the crop as per a soil test. A well-fed crop holds on to its leaves better.
• Bio-agents: the ICAR-NCIPM chilli IPM package advises Trichoderma and Pseudomonas fluorescens (helpful fungus and bacterium) as seed and nursery treatment, as part of general crop health. Ask your local agriculture officer or Krishi Vigyan Kendra (KVK) about a registered product and the rate for your crop.

Fungicide for Cercospora leaf spot of chilli

Only the product below has chilli and Cercospora leaf spot on its official label. The dose is per acre, converted from the label's per-hectare dose. Use one product at a time and do not mix products in one tank. Cover both sides of the leaves, starting with the lower leaves.

Chilli

Product	Contains	Label dose per acre	Water per acre	Wait before harvest
Merger Fungicide	Tricyclazole 18% + Mancozeb 62% WP	506 g	200 L	7 days

Notes from the label:

• Merger: spray when the disease symptoms appear, in the morning or evening, with a high-volume knapsack sprayer. One to three sprays, depending on how bad the disease is.
• Merger holds two active ingredients in one pack. It is a ready-mixed product approved on the label, not a tank mix.
• In chilli you pick fruit many times. Leave 7 days between the last spray and the next picking.

Cotton

None of the products in our store has Cercospora leaf spot on cotton on its label, so we do not suggest one here. Use the non-chemical steps above, and ask your local agriculture officer or KVK for a product labelled for cotton.

Black gram and green gram

None of the products in our store names Cercospora leaf spot on black gram or green gram on its label, so we do not suggest one here. Some labels only say "leaf spot" without naming the fungus. Ask your local agriculture officer or KVK for a product labelled for your pulse crop.

Rotate to avoid resistance

If you spray the same type of fungicide again and again, the fungus can stop responding to it. Fungicides are grouped by how they work, using the FRAC code (FRAC is the international Fungicide Resistance Action Committee). Change the group from one spray to the next.

FRAC group	Active ingredient	Products in this article
16.1	Tricyclazole	One part of Merger
M03 (multi-site contact)	Mancozeb	One part of Merger

Mancozeb (group M03) acts on many points inside the fungus, so the risk of resistance to it is low. It works only where it lands, so good leaf cover matters. If you need more sprays than the Merger label allows, ask your agriculture officer for a chilli-labelled product from a different FRAC group. Keep to the number of sprays the label allows.

Safety and waiting period

• The waiting period before harvest (PHI, pre-harvest interval) for Merger on chilli is 7 days. Count the days from the last spray.
• Wear gloves, a mask, full-sleeve clothes and boots while mixing and spraying. Do not eat, drink or smoke while you work. Wash well afterwards.
• Spray in the morning or evening, in calm weather.
• Fish: the Merger leaflet warns that it is toxic to water life. Keep sprays and washings away from ponds, canals, wells and fish culture.
• Read the label and leaflet before use.

Frequently asked questions

What causes Cercospora leaf spot of chilli?

The fungus Cercospora capsici. It lives on in old crop waste, on seed and on volunteer chilli plants. Wind and rain splash spread its spores, and warm, humid weather helps it.

What does Cercospora leaf spot look like?

Round spots with a light grey or white centre and a dark brown edge, like a frog's eye. TNAU notes the spots can grow to 1 cm or more across. They join together, and the leaf turns yellow and falls. Stems, leaf stalks and fruit get oval spots with a pale centre.

Is Cercospora leaf spot the same in chilli, cotton and black gram?

No. Each crop has its own Cercospora species, and it does not usually jump from one crop to another. The spots look alike, but the fungicide you choose must be labelled for your crop.

Can the disease come through seed?

Yes. In chilli and in black gram the fungus can be carried on seed. Save seed only from healthy plants, or buy certified seed.

How many sprays are needed?

TNAU advises two sprays 10 to 15 days apart in chilli. The Merger label allows one to three sprays, depending on how bad the disease is. Start at the first spots and stop when new spots no longer appear.

Related reading

• Anthracnose of chilli, mango and grapes: symptoms and control
• Powdery mildew fungicide guide for chilli, grapes, mango and wheat
• Alternaria leaf spot and blight in cotton, chilli and mustard
• Bacterial leaf spot in chilli and tomato
• Tikka disease of groundnut: early and late leaf spot
• Products for chilli
• All fungicides

Sources

• Tamil Nadu Agricultural University, TNAU Agritech Portal: Chilli, Cercospora leaf spot
• Tamil Nadu Agricultural University, TNAU Agritech Portal: Cotton, Cercospora leaf spot
• Tamil Nadu Agricultural University, TNAU Agritech Portal: Black gram, Cercospora leaf spot
• ICAR-National Centre for Integrated Pest Management, NIPHM and Directorate of Plant Protection, Quarantine and Storage: AESA based IPM package for chillies and capsicum
• Fungicide Resistance Action Committee: FRAC Code List 2026
• Official label and leaflet of Merger Fungicide