Tomato leaves have white spots

Question

The upper leaves of a fast growing tomato plant has white spots in the top and underside of the leaf. I’m worried that it will spread. The tomato is potted and on a sunny south facing balcony. Is there something I can do to correct this? Pic attached.

Answer 1

This is the common first signs of Septoria leaf spot.
The leaf spots of septoria begin as small yellow specks, which later enlarge, becoming brown with a yellow border. They can be either circular or irregular in shape, and often have a black dot in the center. You will see them scattered all over the older leaves of infected tomato plants. If you feel this is the problem, apply copper dust or a liquid copper spray fungicide every 7 to 10 days after discovering the disease until 3 to 4 weeks before harvesting.
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-bacterial-speck.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/early-blight-alternaria-tomato-leaf-spots-yellow-leaves.htm