Fungal Severity: High ⚠️ Contagious

Southern Blight: Urgent! How to Save Your Plant

Southern blight is a devastating soilborne fungal disease caused by Athelia rolfsii (formerly Sclerotium rolfsii), affecting over 500 plant species including vegetables, ornamentals, and fruit crops. The fungus survives in soil through resting structures called sclerotia that resemble mustard seeds and can remain viable for years.

Spread speed

Fast

Recovery time

21 days

🔍 Symptoms

Main Symptoms

! Brown to black lesions on stem near soil line
! Water-soaked appearance on lower leaves
! Sudden and permanent wilting of entire plant within days
! White mycelium radiating from plant base onto soil surface
! Spherical tan to reddish-brown sclerotia (1-2mm)
! Yellowing and necrosis of foliage
! Crown and root rot
! On fruits: sunken yellow lesions turning water-soaked

Visual Signs

white mycelium radiating on soil surfacetan to reddish-brown spherical sclerotia (mustard seed size)brown to black lesions on stem near soil linewater-soaked appearance on lower leavessudden wilting of entire plantyellowing and necrosis of foliagestem girdling and collapsefruit with sunken yellow lesions turning water-soakedcrown and root rot

Affected parts: StemRootsLEAVESFruitsWhole plant

❓ Possible Causes

→ Soilborne fungus Athelia rolfsii surviving through sclerotia
→ High temperatures (25-30°C / 77-95°F)
→ High soil moisture and relative humidity above 90%
→ Acidic soil (pH below 7, especially pH 2-5)
→ Spread through infested soil and plant debris
→ Contaminated tools, irrigation water, and transplants
→ Contaminated mulch or compost
→ Plant stress and stem injuries

💊 Treatment

⚡

Quick Fixes

~11 days

Step 1

Remove infected plants IMMEDIATELY with roots and soil

Step 2

Apply azoxystrobin drench to adjacent plants

Step 3

Spray mancozeb on base of all plants in area

Step 4

Drastically reduce irrigation

Step 5

Reapply fungicides every 7-10 days for 3 weeks

Materials needed:

Copper-based fungicideHydrated limeTebuconazolePlastic sheeting

🌿

Organic Treatment

~21 days

Step 1

Remove diseased plants and 3 inches of contaminated soil

Step 2

Solarize area with clear plastic for 6 weeks

Step 3

Incorporate compost rich in Trichoderma

Step 4

Adjust soil pH with lime

Step 5

Improve drainage and plant spacing

Step 6

Apply preventive bicarbonate spray biweekly

Materials needed:

Trichoderma harzianumWell-cured compostMustard mealClean mulchGarlic extract

🔬

Expert Treatment

~32 days

Step 1

Map disease hotspots and infestation history

Step 2

Remove all vegetation and 4 inches of soil in critical areas

Step 3

Fumigate soil with chloropicrin if economically viable

Step 4

Deep plow (12 inches) and incorporate lime

Step 5

Apply flutolanil drench before planting

Step 6

Use grafted varieties on resistant rootstocks when available

Step 7

Fungicide rotation program: azole → strobilurin → SDHI

Step 8

Implement subsurface drip irrigation system

Step 9

Continuously monitor soil temperature and moisture

Step 10

Keep detailed records to adjust protocol

Step by Step

1
1. Remove ALL symptomatic plants IMMEDIATELY including roots
2
2. Dig out and discard 3 inches of soil extending 12 inches beyond affected area
3
3. Bag and dispose in landfill (DO NOT compost)
4
4. Disinfect tools with 10% bleach solution
5
5. Deep plow to bury remaining sclerotia
6
6. Apply systemic fungicide to adjacent plants
7
7. Improve drainage and reduce irrigation
8
8. Raise soil pH above 7 with lime
9
9. Monitor daily for new infections for 2-3 weeks
10
10. Rotate affected area with non-host crops for 2-3 years

🧪 Solutions

🌱 Natural Solutions

✓ Remove infected plants with roots and 3 inches of surrounding soil
✓ Soil solarization: cover moist soil with clear plastic for 4-6 weeks in hot weather
✓ Biocontrol agents: Trichoderma spp. applied to soil
✓ Incorporate organic matter rich in beneficial antagonists
✓ Potassium bicarbonate spray (5g/L) preventively
✓ Application of lime sulfur as preventive treatment
✓ Hot composting of plant debris to kill sclerotia