Capsicum & Chilli
Early Blight
Alternaria solani
Fungus
In a Nutshell
- Dark spots on leaves with circles around them and yellow rings around the spots.
- Leaves dry out and fall off.
- Fruits start to rot and fall off the plant.
Can also be found in
Capsicum & Chilli
Symptoms
If a plant has early blight, it will show symptoms on its older leaves, stem, and fruits. There will be gray or brown spots on the leaves that get bigger in circles around a clear center, which looks like a target (the characteristic “bullseye” formation). The spots are also surrounded by a bright yellow ring. As the disease gets worse, the entire leaf may turn yellow and fall off, leaving the plant with fewer leaves. When the leaves fall off, the fruits are more likely to get sunburn. The same type of spots with a clear center also appear on the stem and fruits. The fruits may start to rot and fall off the plant.
Recommendations
Organic Control
Application of products based on Bacillus subtilis or copper-based fungicides registered as organic can treat this disease.
Chemical Control
It is always best to try to prevent the disease and use biological treatments if possible. There are many different fungicides that can be used to control early blight. These products contain chemicals like azoxystrobin, pyraclostrobin, difenoconazole, boscalid, chlorothalonil, fenamidone, maneb, mancozeb, trifloxystrobin, and ziram. It is a good idea to rotate between different chemical compounds. Be sure to apply the treatments on time and consider the weather conditions. Make sure to check how long you need to wait before you can safely harvest the plants after using these products.
What caused it?
The fungus Alternaria solani causes the symptoms of this disease. It can survive in soil on infected plant debris or on other plants over the winter. You may also get infected plants by purchasing seeds or seedlings that are already contaminated. The lower leaves are often infected when they touch contaminated soil. The fungus grows better when it is warm (24-29°C) and very humid (90%). A long period of wet weather or wet and dry weather can help the fungus produce spores, which can be spread by wind, rain, or overhead irrigation. If your crop is potato, green or wet potatoes are more likely to get infected with the fungus. The disease often appears after heavy rain and is especially damaging in tropical and subtropical areas.
Preventive Measures
- Use seeds or plants that are certified to be free of the disease.
- Look for varieties that are resistant to the disease.
- Plant or transplant the plants on raised beds to improve drainage.
- Plant the rows in the direction of the wind and avoid shady areas.
- Leave enough space between plants so that the tops of the plants dry quickly after rain or irrigation.
- Cover the soil with mulch to keep the plants from touching the soil.
- Watch for signs of the disease, especially during wet weather.
- Remove the bottom leaves that are too close to the soil.
- Remove any leaves that show symptoms of the disease and destroy them.
- Keep the plants healthy and strong with good fertilization.
- Use stakes to keep the plants upright depending on the crop.
- Use a drip irrigation system to minimize the amount of time the leaves are wet.
- Water the plants in the morning so they have time to dry during the day.
- Control weeds that are susceptible to the disease around the field.
- Avoid working in the field when the plants are wet.
- After harvest, remove all plant debris and burn it (do not compost it) or bury it deep in the soil (more than 45 cm).
- Plant different crops in the field over two or three years.
- For potatoes, store the tubers in a cool place with good air circulation.
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