Answer: Tomatoes are subject to a number of bacterial and fungal infections. Unfortunately, based on your description I am not able to diagnose the problem with your tomatoes. I would suggest you consult with your Penn State cooperative extension to obtain a specific diagnosis. If a chemical control is needed, they will have the most up to date information on what to use and how/when to apply it for best results.
In the meantime, remove any infected branches and foliage and dispose of it in the trash to try to limit sources of reinfection. Also, if you water your plants apply it to the soil surface and avoid wetting the foliage. Finally, do not handle the plants when they are wet from rain or dew.
This fall, be sure to do a thorough clean up of the garden and dispose of all the tomato plants in the trash and then rotate your planting so you do not replant tomatoes in the same location for several years. This is another way of trying to prevent reinfection from one year to the next.
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