Plesiomonadosis

Plesiomonadosis is a bacterial plant disease caused by the pathogen Plesiomonas shigelloides. While this bacterium is primarily recognized in medical and veterinary microbiology, it acts as an opportunistic phytopathogen that causes tissue degradation in various horticultural crops, particularly those grown in aquatic environments or heavily irrigated soil.

The host range includes leafy greens, vegetables, and certain aquatic crops. Infection typically occurs when plants come into contact with contaminated water sources, such as irrigation channels containing fecal runoff or untreated wastewater. The pathogen exploits small wounds and natural plant openings to invade the plant parenchyma, leading to localized tissue necrosis.

Symptoms of the disease involve the development of rapidly spreading water-soaked lesions on leaves and stems. As the infection progresses, the affected tissue undergoes soft rot, turning mushy and emitting a distinct odor. In advanced stages, the plant tissue collapses completely, rendering the produce unmarketable and posing a risk of secondary infection to neighboring plants.

Disease development is highly dependent on environmental factors, favoring temperatures between 25°C and 35°C and high humidity levels. These conditions facilitate the multiplication of the bacteria and the production of extracellular enzymes that break down plant cell walls. Persistence in the soil and contaminated water supplies makes the pathogen difficult to eradicate once it is established in an agricultural system.

Effective management requires a multi-faceted approach. Primary prevention involves the regular monitoring of irrigation water quality and the exclusion of any potentially contaminated run-off. Agronomic practices should focus on maintaining plant health, reducing mechanical damage to tissues, and ensuring proper sanitation of farming tools and storage facilities. Crop rotation and the prompt destruction of infected plant debris remain essential for minimizing future inoculum pressure.