by National Gardening Association Editors
The most common bean diseases are: Anthracnose, bacterial blights, common bean mosaic, and rust.
Common Bean Diseases
Anthracnose is caused by a fungus, which is carried in seeds and lives in the soil on the remains of diseased plants. Rotating crops is important for control. You can recognize the disease by the brown, sunken spots that develop on the pods.
Bacterial blights cause large, brown spots on the leaves and water-soaked spots on the pods. The disease spreads quickly on wet foliage.
Common bean mosaic is caused by a virus carried in the seed and spread by aphids. Leaves become mottled and then curl. Some bean varieties are resistant to this disease.
Rust shows as red or black blisters on the leaves, which turn yellow and drop. The problem is caused by a fungus that lives through the winter on the remains of diseased plants.
When anthracnose, blights or other bean diseases hit, there isn't too much you can do except to pull up and destroy seriously affected plants to prevent the disease from spreading to nearby plants. A few sprays are recommended to fight diseases. Contact your extension service agent for more information before using them. Extension agents are usually aware of which diseases have developed in an area and what the best controls are.
Disease Prevention Steps
Here's a quick review of the basic steps to preventing disease problems in your garden:
- Stay out of the garden when plants are wet, because water is often the carrier of diseases.
- Rotate the bean crop each year to avoid soilborne diseases.
- Select disease-resistant seed varieties, and buy seed from a reputable company. You can use seed protectant on beans, too.
- Well-drained soil is important for growing beans.
- If the soil stays wet, raised beds are your best bet for beans. With raised beds the soil will be warmer at planting time, and the seedbed will drain better. Raised beds are also good for heavy soil because it won't pack down as much.
- Use mulch in the walkways and wide-row growing to prevent raindrops from splashing soil and disease spores up onto the plants.
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