Pseudomonas corrugata

Pseudomonas corrugata is a gram-negative phytopathogenic bacterium recognized as the primary agent of tomato pith necrosis. This vascular disease causes systemic infection, leading to significant economic losses in both greenhouse and field-grown tomato crops. The pathogen is known for its ability to persist in soil and agricultural equipment, surviving as a saprophyte on plant debris when living hosts are unavailable.

While tomatoes are the primary host, the disease can impact various Solanaceae crops. The bacteria gain entry into the plant through natural openings such as stomata or via mechanical wounds created during pruning, harvesting, or by insect vectors. Once inside, the bacteria multiply rapidly within the xylem vessels, obstructing water and nutrient transport, which causes the characteristic sudden wilting of the plant.

Symptoms are most visible on the stems and leaves. Initial signs include chlorosis of younger leaves, followed by wilting that occurs even under adequate irrigation. A definitive diagnostic symptom is found by slicing the stem vertically; the pith shows dark brown discoloration, cavities, and necrosis. In severe cases, the stem may split, or the plant may show adventitious root formation along the infected stem sections as a response to vascular damage.

The development of the disease is highly correlated with environmental stressors. High humidity levels (often exceeding 90%) and cool night temperatures (below 20°C) significantly favor bacterial proliferation. Management is further complicated by cultural practices such as overhead irrigation, which splashes bacteria onto foliage and wounds, and excessive nitrogen fertilization, which results in succulent, susceptible growth.

Effective control relies primarily on preventive agricultural practices rather than chemical eradication. Producers should focus on the following strategies:

• Ensuring the use of certified disease-free seeds and seedlings.
• Rigorous sanitation, including sterilizing pruning tools with disinfectants between every plant.
• Managing greenhouse humidity levels through improved ventilation and drainage.
• Avoiding excessive use of nitrogen fertilizers and ensuring balanced potassium levels.
• Removing and incinerating infected plant material immediately upon detection.