Q: I have several tomato plants with plenty of fruit. My problem is that on nearly all of them the area around the stem looks hard and dark in an irregular pattern like a worm worked on it but I have yet to see or find any caterpillars. Any suggestions?
A: I think the fruit has been damaged by early blight fungus. This disease is common on tomato leaves, turning them bright yellow before they drop off. When it infects fruit, it causes a sunken spot around the stem. This spot may enlarge or it may remain relatively contained.
When I helped my mother can tomatoes as a kid, we sliced the bad part out and tossed the good part of the fruit into the boiler. You can do the same before eating your tomatoes.
Texas A & M has a great site for identifying tomato problems at