How do bacteria primarily spread diseases in plants?

Bacteria primarily spread diseases in plants primarily through injuries to the plant. When a plant experiences physical damage from mechanical injury, pests, or environmental factors, the protective barriers—such as cuticles and cell walls—are disrupted. This exposure allows bacteria to enter the plant's system more easily, leading to infection.

Injuries create an entry point for pathogens, which can then colonize the plant tissues and disrupt normal physiological functions, leading to symptoms of disease. This mechanism is essential for understanding plant pathology, as managing injuries and physical stress in plants can significantly reduce the risk of bacterial infections.

While other options like infected soil, seeds, and insects do contribute to disease spread, they often rely on pre-existing conditions where injuries have already allowed bacterial entry, amplifying the risk and spread of the disease within populations of plants.