Klebsiella bacterial rot

The characteristic sign of the disease is the rapid development of water-soaked, translucent lesions on leaves, stems, or succulent fruits.

As the infection progresses, these areas turn soft, mushy, and often emit a pungent, foul odor due to the fermentation process of the plant tissues.

Vascular browning and systemic wilting are observed when the bacteria invade the transport vessels, blocking water and nutrient flow to the upper parts of the plant.

In high humidity, a characteristic bacterial ooze, often creamy or white in appearance, may be visible on the surface of the rotted areas.

Roots infected with the pathogen become necrotic, turning brown or black and losing their structural integrity, which results in the sudden wilting of the plant.

The causative agent of the disease is the facultative anaerobic gram-negative bacterium Klebsiella aerogenes, a member of the Enterobacteriaceae family.

This pathogen possesses high metabolic versatility, allowing it to survive in diverse environments including soil, water, and decaying organic matter.

The bacteria secrete cell wall-degrading enzymes, such as pectinases and cellulases, which break down plant tissue integrity to facilitate colonization.

Transmission of the pathogen occurs primarily through water splashes, contaminated tools, infested seeds, and insect vectors that move between plants.

Klebsiella aerogenes is highly adaptable and can infect a wide range of horticultural and field crops, functioning as an opportunistic plant pathogen.

Development of the disease is highly favored by high relative humidity (above 80%) and temperatures ranging from 22°C to 30°C.

Poor ventilation within greenhouses, resulting in persistent condensation on foliage, significantly accelerates the spread of bacterial populations.

Mechanical injuries resulting from handling, pruning, or feeding by pests provide essential entry points for the bacteria to colonize the host tissues.

Excessive irrigation and waterlogged soil conditions stress the plant and facilitate the movement of bacteria through the soil and root zone.

Plants with an imbalanced nutrient profile, particularly those with excessive nitrogen fertilization, are more susceptible to the soft rot syndrome.

Klebsiella bacterial rot can cause devastating crop losses during the growing season, especially under conditions of prolonged rain or humidity.

It is a significant post-harvest disease, as infected produce can contaminate entire storage facilities if not properly sorted and managed.

The disease reduces the quality and marketability of vegetables and fruits, making them unfit for consumption due to the rapid liquefaction of tissue.

The economic impact is exacerbated by the necessity for expensive disinfection of agricultural tools, storage equipment, and production fields.

Persistent infestations in the soil can lead to long-term issues, requiring growers to change their crop rotation plans for several consecutive seasons.

Integrated management is essential, focusing primarily on prevention through the use of high-quality, disease-free seed and propagation material.

Cultural practices such as improving field drainage and ensuring adequate spacing between plants are critical to minimize humidity levels.

• Strict removal and disposal of all infected plant debris;
• Regular sanitation of agricultural tools and equipment;
• Implementation of a 3-year crop rotation with non-host plants;
• Efficient control of insect vectors like aphids and whiteflies.

Preventive applications of copper-based bactericides can help reduce bacterial inoculum on the surface of the plants before infection takes hold.

Post-harvest hygiene, including maintaining dry and cool conditions in storage, is critical to preventing the secondary spread of the bacterium.