Basil Leaf Spot – Identification

Q: This week I noticed black spots on the leaves of my basil. Today, I saw these weird dots/bumps on the stems. Are they eggs of a bug or maybe a plant disease?

A: At first I thought the brown things on the stem were scale insects.

But on looking closer, I think they are adventitious roots that formed in reaction to the stress of a bacterial infection, specifically Pseudomonas cichorii.

Black spots on the leaves are characteristic of this bacterial leaf disease.

There’s not much you can do now to save your plant but if there are green leaves with no spots I would have no problem eating them after washing.

Wet weather certainly has a lot to do with bacterial diseases. If we have a dry spring and summer this disease won’t show up.

Basil Leaf Spot