Septoria lycopersici
Common fungal disease of tomatoes causing numerous small spots on lower leaves. Progresses upward, causing severe defoliation.
Small circular spots with dark borders and tan/gray centers. Tiny black dots (pycnidia) visible in spot centers. Lower leaves affected first. Severe defoliation.
Fungal pathogen that overwinters on infected plant debris. Does not affect fruit directly but reduces yield through defoliation.
Splashing water from rain or irrigation. Spores spread from lower leaves upward. Contaminated tools and hands.
Warm temperatures (60-80°F). Extended leaf wetness. Frequent rain or overhead irrigation. Dense plantings.
Stake or cage tomatoes. Mulch around plants. Avoid overhead watering. Remove plant debris in fall. Rotate crops 2-3 years.