Black spots on tomatoes and vines

Asked July 6, 2017, 9:19 PM EDT

This is my first year having a garden and tomatoes are all over but they are turning black on the bottom and I notice some of the vines have black spots as well. What is this and can I do something to fix it. Also will it cause harm to my squash and other vegetables. Thanks for your help.

Ramsey County Minnesota vegetables tomato problem horticulture tomatoes

2 Responses

Thank you for the question. It appears your tomatoes are infected with a fungal infection of some kind, maybe early blight. I have sent your question to our Extension expert on plant diseases and will get back to you if I hear a different diagnosis.

Early blight is a very common, highly contagious fungal infection of tomatoes wherever they are grown. Your photos match the description of the disease in many ways. Control measures include planting resistant varieties, cleaning up and disposing of all plant debris at the end of the season, avoiding overhead watering and working in the garden when the plants are wet, rotate tomato growing to a different spot in the garden at least every 2 years, proper staking to promote airflow between plants and to keep plant leaves from touching. Please read our publication on the disease to learn more:
This publication from Rutgers has good general control measures for fungal diseases: https://njaes.rutgers.edu/pubs/fs547/

Thank you for contacting Extension.

Michelle Grabowski, Extension Plant Pathologist responded and I will summarize:
"It's hard to say which disease is affecting these tomatoes. It looks like blossom end rot on the fruit but with wide flat tomatoes like these we sometimes see catface that causes cracks and then becomes infected with a secondary rot organism. The possible pathogens causing spots on leaves, stems and fruit include bacterial spot, septoria leaf spot and early blight. Septoria typically does not cause fruit spots but I have seen it on some heirloom varieties. All 3 conditions are treated the same.
The plants are really wet and all 3 diseases are favored by moisture on the fruit and foliage. At this time of year focus on removing and composting infected fruit and leaves in addition to doing whatever you can to keep the leaves and fruit dry. At the end of the season completely remove and compost the plants and plant tomatoes in a different location next year if possible. Please read the following publications:


Tomato Pest Identification and Management

Growing healthy vegetables