Bacterial canker

Bacterial canker, caused by the bacterium Clavibacter michiganensis, is a highly destructive vascular disease affecting solanaceous crops worldwide. The pathogen colonizes the xylem vessels, obstructing water and nutrient flow, which causes systemic wilting, stunted growth, and the eventual death of the affected plant tissues.

The host range of Clavibacter michiganensis is significant, extending beyond tomatoes to include sweet pepper and various other crops. Reports indicate that this pathogen can affect or persist on plants such as peanuts, papaya, watermelon, dahlia, carnation, strawberry, and soybean, making it a multifaceted challenge for integrated pest management programs.

Diagnostic symptoms often begin with wilting and marginal necrosis of leaves, which may curl upwards. On the stems, longitudinal cracks can develop. A hallmark sign on fruit is the formation of small, raised white spots with dark centers, known as «bird's eye» spots. Inside the stem, vascular browning is a definitive symptom of systemic infection.

Environmental conditions characterized by high humidity and temperatures between 24°C and 28°C favor the rapid multiplication and spread of the bacteria. The pathogen is easily disseminated through infected seeds, contaminated tools used during pruning, irrigation water, and even through direct contact between diseased and healthy plants during cultural practices.

Management strategies focus primarily on prevention, as curative chemical options are limited. Essential practices include using certified disease-free seeds, implementing strict greenhouse sanitation, and sterilizing tools with appropriate disinfectants. Crop rotation and the removal of infected plant debris are crucial to reduce the inoculum level in the soil and prevent future outbreaks.