Sclerotinia stem rot of potato

The disease is caused by the fungus Sclerotinia sclerotiorum, which is widely known as white mold. It is a highly aggressive pathogen that attacks many broadleaf plants. Its ability to survive in the soil as hard black structures called sclerotia for many years makes it an extremely persistent threat in agricultural fields.

Symptoms initially appear on the stems, particularly near the soil line. Infected areas look water-soaked and eventually turn pale or bleached. Under humid conditions, a characteristic fluffy white fungal growth develops on the lesion surface. Eventually, the stem tissue breaks down, leading to wilt and collapse of the entire plant stem.

The spread of the disease is heavily dependent on environmental conditions, particularly moisture. High soil moisture and frequent rainfall create the necessary conditions for sclerotia to germinate and produce spores. Once airborne, these spores land on vulnerable potato foliage, initiating new infections, especially in dense crop canopies where airflow is restricted.

The economic impact of Sclerotinia stem rot is severe. Infected stems cannot transport nutrients effectively to the tubers, leading to stunted growth and reduced tuber yield. Additionally, if the rot affects tubers or enters storage, the disease can cause significant post-harvest losses, potentially destroying entire batches of produce.

Effective management requires an integrated approach to break the disease cycle. Crop rotation is essential, preferably using non-host crops like cereals or corn. Improving field drainage and maintaining appropriate plant spacing to ensure air circulation are critical cultural practices. In high-risk areas, the timely application of fungicides remains the standard chemical defense against the spread of the pathogen.