You can see how the blight affects the stem and leaves of the tomato plant. Yuck.
We've still got some healthy tomatoes, so we're hanging in there and destroying infected fruit. I dumped a 20-liter bag of rotten tomatoes into the garbage can last week. So sad. The blight shows up in the leaves first, then moves into the stems. When fruit forms, the fungus quickly infects it as well.
Two infected tomatoes before I removed them. The stem to the left is completely brown.
I read about blight and there's not a lot a home gardener can do once it sets in. The best measures are preventative: remove infected plants at the first sign of the fungus (I didn't do that), bag or burn infected leaves, plants, and fruit, and spray bouillie bordelaise (a copper sulfate mix) on the plants before blight appears (I didn't do that, either).
I usually rotate the crops around the garden plots so that I'm not growing the same thing in the same place every year. That will be especially important next year. I will also have to be vigilant about removing volunteers and removing excess leaves from the plants to allow a good air flow. I will also use bouillie bordelaise or some other anti-fungal treatment early in the season to help keep the blight at bay.