White mold on eggplant — symptoms and treatment

Severity: high

What is White mold

White mold (Sclerotinia sclerotiorum) causes a soft, watery rot covered with white fluffy mycelium. On eggplant it attacks stems and fruit, and once it has girdled a stem everything above the infection point wilts and is lost. The fungus thrives in cool, humid conditions and survives between crops as hard black resting bodies called sclerotia, which is what makes it a high-severity, hard-to-shake problem rather than a passing blemish.

Symptoms

Look first at the base of the plant and anywhere stems are crowded or shaded. Infection shows as a soft, watery rot of the stem tissue — the affected area goes pale and mushy rather than dry and brown. In humid weather the rot is quickly covered by white, cottony fungal growth that looks like a scrap of cotton wool stuck to the stem. As the stem is girdled, everything above the infection wilts while the rest of the plant may still look fine. The confirming sign is internal: split an affected stem and you will find hard black sclerotia, seed-like lumps, sitting inside the pith.

• Early: soft, watery rot on a stem or on fruit; pale, mushy tissue
• Advanced: white cottony mycelium over the rot; wilting of everything above the infected area
• Diagnostic: hard black sclerotia inside split stems

The soft rot alone can be mistaken for other stem and fruit rots. The combination of white fluffy growth plus black sclerotia inside the stem is what makes it White mold.

Causes and conditions

Sclerotinia sclerotiorum survives in the soil as sclerotia. These germinate in cool, humid conditions and produce spores that land on the crop, colonising dead or dying tissue first — old flowers, wounds, leaves lying on the soil — then moving into healthy stems from that bridgehead. Dense canopies, poor air movement, wet soil surfaces and lush growth from heavy nitrogen all favour it. New sclerotia form in the rotted tissue and return to the soil when infected material is left in the bed.

Treatment

Lead with cultural measures — they change the conditions the fungus needs. A fungicide protects healthy tissue but will not resurrect a rotted stem.

Spacing and debris removal — cultural

Timing: throughout the season. Increase plant spacing for air circulation. Remove infected plant parts. Avoid excessive nitrogen fertilization.

Wider spacing lets the canopy dry, removing the humid microclimate the fungus needs. Carry infected plant parts away rather than dropping them in the bed, so their sclerotia do not return to the soil. Easing off nitrogen keeps growth firmer.

Iprodione — chemical

Timing: preventive in humid weather. Apply fungicide preventively in cool, humid conditions. Target the base of plants where infection starts.

Pre-harvest interval: 14 days.

Pesticide registrations vary by country — check local approval before use.

Prevention

• Space plants generously and keep the canopy open so foliage dries quickly.
• Water at the base and avoid wetting stems and fruit.
• Keep fruit and low leaves off wet soil; mulch or stake as needed.
• Remove and destroy infected plants and debris — never compost them.
• Avoid excessive nitrogen, and rotate away from susceptible crops in beds with a history of the disease.

Frequently asked questions

Can I eat fruit from a treated plant? Yes, once the pre-harvest interval has passed: after an Iprodione application, wait 14 days before picking. Fruit that is already soft and rotting should be discarded.

Is White mold contagious to other plants? Yes. Spores spread to nearby plants and the sclerotia left behind infest the soil, so an untreated patch is a source for the rest of the bed and for future crops.

When should I spray? Preventively, when cool humid weather sets in — before you see rot. Target the base of the plants, where infection usually starts.