Bacterial spot of pepper and tomato

The pathogen Xanthomonas euvesicatoria belongs to the domain Bacteria, phylum Proteobacteria, class Gammaproteobacteria, order Xanthomonadales, family Xanthomonadaceae, and genus Xanthomonas. It is a Gram-negative, rod-shaped bacterium known primarily as the causative agent of bacterial spot disease in solanaceous crops.

The disease primarily affects tomatoes and peppers. Initial symptoms appear as small, water-soaked spots on leaves, stems, and fruit. Over time, these spots darken to brown or black, often surrounded by a characteristic yellow halo. Heavy infections lead to foliage drop, stunted growth, and unmarketable fruits due to unsightly, scab-like lesions.

The life cycle of the pathogen is dependent on environmental conditions and plant health. The bacteria overwinter on contaminated seeds, infected crop debris, and perennial weed hosts. Transmission of the disease occurs mainly through splashing rain, irrigation water, agricultural tools, and handling practices during seasonal crop management.

Optimal conditions for Xanthomonas euvesicatoria development include high relative humidity (above 80%) and temperatures between +24°C and +30°C. The pathogen enters the host plant through stomata, hydathodes, or small wounds caused by insects or mechanical damage. Once inside, the bacteria multiply rapidly within the intercellular spaces of the plant tissue.

The economic impact of this pathogen is severe, often resulting in significant yield losses in both greenhouse and field production. Effective control strategies include:

• planting pathogen-free, certified seeds;
• hot-water or chemical seed treatments;
• strict crop rotation with non-host crops for at least 3 years;
• thorough removal and destruction of crop residues;
• regular application of copper-based bactericides during conducive weather conditions.