spotted tomato leaves
Thank you for your note to eXtension.
There are several leaf spot diseases that can affect tomatoes. The more common ones are caused by fungi, and are reasonably easy to control.
However, I am not confident that this is a fungus disease. I'm thinking it looks more like bacterial speck. The only sure-fire way to know is to send samples to the Purdue Plant and Pest Diagnostic Lab. The lab will charge you $11 to identify this disease and provide recommendations for control; you may be able to get an answer back quickly enough to save your plants. If you wish to go this route, please contact your county's Extension Ag Educator, Curt Emanuel (firstname.lastname@example.org ).
If you don't wish to go this route, you can try spraying the plants with a fungicide that contains copper. These are normally found with the other organic pesticides in the garden center. Follow all label directions.
Other things you can do: If you are watering, try to avoid getting the leaves wet by using a soaker hose. If that's not possible, then water early in the morning: the leaves will quickly dry off as the sun rises, and this prevents the spread of both bacterial and fungal leaf spots. Also, when the plants are dry, you can try to remove some of the diseased leaves by hand.
Please let me know if you have any other questions.