Black stems on Red Racer Tomato plant

Asked July 8, 2020, 3:14 PM EDT

The tomato plant is in a large self-watering container. It seemed very healthy, beginning to set fruit, then 2days ago I noticed the blackened stems. It has been over 90 degrees for several days and very humid. The growing soil has had an infestation of fungus gnats (which Ive controlled with Azamax). Does this look like Alternaria? I am worried abt it spreading to eggplant and cucumber abd otger tomato plants.

Kent County Michigan

1 Response

Hello,

Are the darkened stems firm or mushy? For alternaria, I would look for concentric rings in blighted areas on the lower leaves of tomato plants (https://extension.umn.edu/diseases/early-blight-tomato).

As for spreading, I don't see alternaria that often in eggplant. The strain of alternaria that impacts tomato does not impact cucumbers.