Bacterial soft rot

The causative agent of this disease is the bacterium Dickeya dadantii, a highly destructive pathogen within the Pectobacteriaceae family. It is identified as a soft rot pathogen that causes tissue maceration by secreting extracellular enzymes such as pectinases. This biochemical process breaks down the middle lamellae of plant cells, causing systemic collapse and necrosis of the host tissues.

This bacterium has a remarkably broad host range, posing a significant threat to various agricultural and ornamental crops. Among the most notable hosts is the sweet potato, where the pathogen can cause severe post-harvest and field losses. Other susceptible hosts include potatoes, carnations, various succulents, and numerous vegetable crops grown in both greenhouse and field environments.

Symptoms often manifest as dark, water-soaked lesions on stems, leaves, or roots. In advanced stages, the infected tissue becomes soft and watery, frequently emitting a foul odor due to the rapid disintegration of cell walls. Wilting is a hallmark of the systemic infection, particularly in sweet potato vines, where the decay can quickly extend from the base into the storage roots.

The development and spread of Dickeya dadantii are heavily influenced by environmental conditions, particularly high humidity and warm temperatures, typically ranging from 25°C to 30°C. The bacteria are primarily transmitted through contaminated vegetative propagation material, irrigation water, movement of soil, and contaminated farm equipment. They enter the host through wounds or natural openings like stomata.

Effective management focuses on exclusion and sanitation, as there are no curative chemical treatments for systemic bacterial soft rot. Producers must prioritize the use of certified, disease-free planting material. Implementing strict hygiene protocols for tools, practicing crop rotation, ensuring optimal soil drainage to avoid waterlogging, and controlling insect pests are critical strategies to minimize the impact of this pathogen.