The Problem
- Cercospora leaf spot (for example) is caused by the fungus Cercospora beticola, occurs wherever beets, swiss chard, and spinach are grown.
- It can result in significant losses, particularly in late summer when conditions are favorable (high temperatures, high humidity, long leaf wetness periods at night).
- Leafy greens become unsuitable for consumption, and beet roots fail to grow to full size when disease is severe.
- Other forms of leaf spot are caused by bacteria.
Signs of damage
Controls
- Once a plant has been infected with a leaf spot fungus, there is no effective, organic treatment for it.
- The only control is “prevention.”
- Leaf spot can be spread by touch, through seeds, or via soil. Avoid touching all of the plants, one after the other to reduce the spread of spores.
- It survives in vegetative debris that collects along the ground. Therefore, the key to controlling it is to practice good sanitation: picking up and properly discarding all plant waste.
- Infested foliage should be cut out as soon as it’s detected.
- Shears or pruners used in removing it must be disinfected after each cut.
- You don’t need to remove the entire plant unless it is totally covered.
- Provide adequate fertilizer. With proper nutrition, plants can actually fight off the bacteria. (As with humans, the more healthy we are, the more able we are to fight off bacteria quickly.) Feed any affected plants with an all-purpose fertilizer at the recommended frequency. Remember, too much fertilizer is a bad thing, too, as high salts in the soil can lead to worse disease issues.
- Finally, as in dealing with any ubiquitous threat, proper crop rotation can help control this disease.