Spots on hydroponic lettuce - Ask Extension
These spots have showed up on hydroponically grown lettuce, is it bacterial or fungal? Or just a nutrient issue?
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Spots on hydroponic lettuce #922812
Asked December 11, 2025, 12:18 PM EST
These spots have showed up on hydroponically grown lettuce, is it bacterial or fungal? Or just a nutrient issue?
Polk County Iowa
Expert Response
The initial examination of this photo suggests a bacterial leaf spot. It can also be a fungal leaf spot, such as Septoria or Cercospora.
There may also be more than one issue here.
Bacterial spots can be difficult to manage. The following can aid in the control:
With all of this said, it is not possible to identify a plant disease from photos alone. The best way to control the issue is to have it accurately identified by the Plant and Insect Diagnostic Clinic. More information on how to contact them and send in a sample can be found here: https://yardandgarden.extension.iastate.edu/pidc
--Aaron
There may also be more than one issue here.
Bacterial spots can be difficult to manage. The following can aid in the control:
- Use only inspected, healthy transplants.
- Avoid working around plants when the foliage is wet.
- Applications of a fixed-copper fungicide can slow the spread of the disease, but will not eradicate existing infections.
- Remove infected plant debris and thoroughly clean the hydroponic setup. Disinfecting the system will look like disinfecting pots: https://yardandgarden.extension.iastate.edu/how-to/how-clean-and-disinfect-plant-containers
With all of this said, it is not possible to identify a plant disease from photos alone. The best way to control the issue is to have it accurately identified by the Plant and Insect Diagnostic Clinic. More information on how to contact them and send in a sample can be found here: https://yardandgarden.extension.iastate.edu/pidc
--Aaron
