fungus on tomatoes
"last year everyone in my area (s.w. NH town) was having issues with a black spotting on the leaves of their tomatoes around the time they were to turn from green to orange. This was in a large area away from where my garden is so I don't think it was just my soil. I was told when I described it to our local extension that it was a fungus. If that was the case, why were so many hit with it? I started my tomatoes from seed on my back deck so it doesn't seem they came with anything."
Submitted by BHGPhotoContest

It sounds like you might have encountered Late Blight. Late Blight is an airborne fungal disease that’s most common after cool, wet weather. Late Blight causes dark leaf spots. The leaves usually turn yellow and drop off. The best way to control any fungal disease is good hygene and crop rotation, but tomato blights are hard to get rid of once they are established in the garden. Pull up and get rid of vines. Don’t put them in the compost pile because they can live there unless you turn the pile often and it really heats up. The fungus can overwinter in the soil, so rotate your plantings every year. You may be able to keep blight down by mulching heavily and never watering your tomatoes from the top. Water the soil at the base of the plant, don’t let the water splash soil on the plants, and space plants far enough apart for good air circulation. Good luck.

Answered by BHGgardenEditors