How do bacterial leaf infections often appear during humid weather?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Blight — Plant disease Potato leaf infected with a fungal blight.

During humid weather, early stages of bacterial leaf infections often appear as dark, water-soaked spots on the foliage. These lesions typically feature a distinct margin and may be surrounded by a lighter-coloured ring known as a halo.1

The development of these infections is heavily influenced by moisture, as a film of water on plant surfaces is generally essential for bacteria to multiply and establish an infection. High humidity levels facilitate this process, as moisture is required for the initiation of infection and the penetration of the pathogen into the plant tissue.23