Septoria leaf spot
Septoria leaf spot is a fungal disease caused by the pathogen Septoria. It primarily affects the leaves of plants, creating small, circular spots that are usually brown with a lighter center. Over time, these spots can coalesce, leading to leaf yellowing and premature leaf drop.
About this problem
Septoria leaf spot is a common fungal disease affecting a wide range of plants, particularly tomatoes. The disease is caused by the fungus Septoria, which thrives in warm, wet conditions. It typically begins on the lower leaves of the plant and progresses upwards. The initial symptoms are small, water-soaked spots that develop into circular lesions with dark brown margins and lighter centers. As the disease progresses, the spots may merge, causing significant leaf damage and yellowing. This can lead to premature leaf drop, reducing the plant's photosynthetic capacity and potentially impacting yield. Septoria leaf spot is often confused with other leaf spot diseases, but its distinctive spotting pattern helps in identification.
Symptoms
- Small, circular brown spots on leaves
- Yellowing of leaves
- Premature leaf drop
- Lesions with dark margins and light centers
Cause
The disease is caused by the fungus Septoria, which spreads through water splashes, wind, and contaminated tools. It thrives in warm, humid conditions.
Conditions that favour it
- High humidity
- Warm temperatures
- Poor air circulation
- Frequent rain or overhead watering
Lifecycle and spread
Septoria overwinters in plant debris and can spread through water splashes, wind, and contaminated tools. Breaking the cycle involves removing infected plant debris and improving air circulation.
Plants most affected
- Tomato
- Eggplant
- Pepper
- Potato
- Cucumber
- Squash
- Melon
- Bean
- Spinach
- Lettuce
Treatment
Educational information only, and not a substitute for professional diagnosis. Identify the problem before treating it, and check that any product is registered for this plant and this use where you live.
Cultural control
- Remove and destroy infected plant debris
- Ensure proper plant spacing for air circulation
- Water at the base of plants to avoid wetting foliage
- Rotate crops to prevent disease buildup
Organic options
- Neem oil
- Copper-based fungicides
- Bacillus subtilis
Chemical options
- Chlorothalonil Used to manage fungal leaf spots
Read and follow the product label. The label is the legally binding instruction. Confirm the product is registered for this plant and for this use in your area before applying it.
Prevention
- Practice crop rotation
- Use disease-free seeds and transplants
- Maintain proper plant spacing
- Avoid overhead watering