Algal leaf spot is a foliar disease caused by algae, primarily affecting tropical and subtropical plants. The main culprit is usually Cephaleuros virescens, a parasitic green alga. While it rarely causes serious harm, it can affect the aesthetics of your plants. These spots usually come together to form large irregular patches on a leaf. As the spots mature they take on a dull, grayish green color.
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Type of Infestation: Disease
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Common Name: Algal leaf Spot
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Causal Organism: Cephaleuros virescens
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Affected Parts Of the plant: Leaves
Environmental favorable factors for pests/Diseases:
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Temperature: Warm temperatures, specifically within the range of 20-32°C (68-89°F), enhance algal growth and disease development. Tropical and subtropical regions are more prone due to consistently warmer temperatures.
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Humidity: This is the single most important factor. Algal leaf spot thrives in high humidity environments (above 70%), as prolonged periods of wet leaves create an ideal environment for algal growth. Humid and rainy seasons exacerbate the problem.
Symptoms of Pest/Disease:
- Small, brown or green spots on the leaves, initially appearing on leaf tips, margins, or near the midvein.
- Spots enlarge to 2-3 mm in diameter and may merge to form larger patches.
- Spots develop a velvety or rough texture.
- Black, irregular spots on immature fruits, which become sunken and cracked as the fruit matures.
- Reduced leaf surface area due to spotting.
- Defoliation in severe cases.
- Dieback of branches in rare cases.
Measures to control Pests/Diseases:
| Products |
Technical Names |
Dosages |
| COC50 |
Copper oxychloride 50 % wp |
2gm/ltr |
| Samartha |
Carbendazim 12 % + Mancozeb 63 % WP |
300-400 grams per acre |
| META MANCO |
Metalaxyl 8 % + Mancozeb 64 % wp |
1.5 to 2 kg per ha |
