Fungal Severity: High ⚠️ Contagious

Septoria Leaf Spot: Urgent! How to Save Your Plant

Septoria leaf spot is a destructive fungal disease caused by Septoria lycopersici, particularly devastating during seasons of moderate temperature and abundant rainfall. The disease starts on lower leaves and progresses upward, causing small circular spots with tan to gray centers and dark brown margins. If left untreated, it can dramatically reduce plant yields and cause complete leaf blight.

Spread speed

Medium

Recovery time

21 days

🔍 Symptoms

Visual Signs

Small circular spots (less than 1/8 inch) with tan to gray centersDark brown margins around lesions, often with yellow halosSmall dark spots (pycnidia) visible in lesion centersLower leaves affected first, progressing upwardSpots coalesce causing complete leaf blightWater-soaked appearance on leaf undersides

Affected parts: LEAVESStem

❓ Possible Causes

→ Fungal pathogen Septoria lycopersici
→ Spores survive up to 2 years in infected plant debris
→ Spread through water splash from rain or overhead irrigation
→ High humidity and moderate temperatures (60-80°F) favor disease development
→ Poor air circulation and wet foliage conditions
→ Infected seeds or transplants
→ Solanaceous weeds acting as disease reservoirs

💊 Treatment

⚡

Quick Fixes

~11 days

Step 1

At first sign of symptoms, apply chlorothalonil-based fungicide

Step 2

Spray thoroughly to cover all leaf surfaces, especially undersides

Step 3

Repeat application every 7 days during favorable disease conditions

Step 4

Remove heavily infected leaves to reduce spore load

Step 5

Ensure good spray coverage on lower canopy where disease starts

Materials needed:

Copper-based fungicideSterilized pruning shearsSpray bottlePlastic bag

🌿

Organic Treatment

~21 days

Step 1

Remove and destroy infected lower leaves carefully while preserving adequate canopy

Step 2

Apply copper-based fungicide (copper diammonia diacetate complex preferred) at early symptom appearance

Step 3

Spray neem oil as foliar application every 7-10 days during wet weather

Step 4

Use baking soda solution (1 tbsp soda + 2.5 tbsp oil per gallon water) as preventative spray

Step 5

Apply compost tea as foliar treatment to boost plant immunity

Step 6

Maintain strict sanitation by removing fallen leaves weekly

Materials needed:

Baking sodaDiluted milk (10%)Neem oilHorsetail tea

🔬

Expert Treatment

~32 days

Step 1

Implement comprehensive field scouting weekly to detect early symptoms

Step 2

Begin preventative fungicide applications before disease appears if conditions favor infection

Step 3

Rotate fungicide modes of action (Group M, Group 11) to prevent resistance

Step 4

Apply azoxystrobin or chlorothalonil on 7-10 day schedule during flowering and fruit set

Step 5

Combine chemical control with cultural practices: improve spacing, prune excess foliage, ensure proper irrigation timing

Step 6

Remove infected plant debris and sanitize equipment between uses

Step 7

Monitor disease pressure and adjust spray intervals based on weather conditions

Step 8

Cease applications based on pre-harvest intervals (PHI): 0-7 days depending on product

🛡️ Prevention

✓ Rotate crops away from tomatoes and related plants for at least 2 years
✓ Remove and destroy all infected plant debris at season end
✓ Use disease-free certified seeds and transplants
✓ Space plants adequately for good air circulation
✓ Stake or trellis plants to keep foliage off ground
✓ Apply mulch to prevent soil-to-leaf contact
✓ Water at plant base early morning using drip irrigation
✓ Avoid overhead watering and working with wet plants
✓ Control solanaceous weeds like horsenettle
✓ Sanitize tools and equipment between uses

🌿 Common in These Plants

African Milk Tree

Heartleaf Philodendron

Moon Orchid