I am trying to figure out what’s going on with my tomatoes. I am a new gardener, have done lots of research, but I don’t have experience to compare it to.
I have several varieties of tomatoes in my bed this year – Cherokee, borghese, san marzano and Roma. My tomatoes are fruiting and the bed looked good- little yellowing, but no spots that I noticed on Friday.. over the weekend, ot became covered in greyish spots, not a lot of yellow, and at this point the fruit doesn’t seem affected.
I think it’s either late blight, verticillium or drought…
This is the first year tomatoes have been grown in this location. Clay soil, but amended with lots of compost, thick layer of mulch, and zone 5b I think
Lots of sun.
Thank you for your help!
This looks like stress from drought, rather than Verticillium Wilt, Early Blight or any of the other leaf spot fungal diseases that tomato plants are prone to. Verticillium wilt is very common at this time of year, but characteristically your leaves would turn yellow rather than the blotching that is shown in your photograph. The leaf spot diseases most often present with small dark round blotches. Grayish blotching can be a symptom of leaf mold, which is another common fungal disease, but appears only on the underside of the leaves (and is incidentally very common on basil plants at this time of year).
Please take a look at this blog post from Cornell University which has good images of the effects of drought on tomato foliage: https://blogs.cornell.edu/livegpath/gallery/tomato/drought-stress/ There is also a link to photos showing tomatoes affected by the fungal disease Late Blight, but the numerous leaves affected at the same stage on your plants suggest drought stress.
Given the very hot and humid weather conditions we have been experiencing, drought stress is certainly possible, and since the fruit is not affected, you could simply carry on with good irrigation and keep an eye on your ripening tomatoes. If your leaves begin to yellow, it is possible that Verticillium Wilt is the culprit. If your plants are growing very closely together, you could remove some of the lower leaves which will improve air circulation between plants. This is an interesting article that discusses removal of tomato foliage and concludes that if disease is a problem, it is a good practice:
August 24, 2021