It sounds like Blossom End Rot (BER). See the link below:

Chris

Here is a link that might be useful: Texas A&M Tomato Problem Solver (BER page)

Chris,
Thanks for your reply, but the damage experienced is at the top of the fruit rather than the blossom end. Garaj

Sorry about that - it appears I don't know my calyx from a hole in the ground. :) Anyway, did you look over the problem solver website? Also, there's a thread in this forum ("HELP!!!! Tomato Problem Solver 2") that has several more websites and other references.

Good Luck,
Chris

Occasionally, I lose a fair number of green, unripe tomatoes to what I believe is stink bug attack. The damage manifests itself as a dark, almost black, slightly sunken area underneath or adjacent to the calyx. No other area of the fruit is affected.I have never noticed stink bugs on the plants. Can anyone confirm that the damage described is indeed typical of stink bug feeding?

I'm curious why you think it's stink bugs because (1) I wouldn't expect to see stink bug damage concentrated at / under / around the calyx. IME, they will damage a fruit all over. (2) Stink bug damage usually manifests itself as a hard whitish (or light colored) corky spot in the fruit, and not dark and sunken. (However, one can occasionally experience some rot due to the damage) (3) You've said that you're not seeing stink bugs on the plants.

So, I tend to think something else is causing the damage. Could be any number of things including pinworms, etc. I'd encourage you to look through the problem solver if you haven't done so yet.

What are you seeing when you cut open the fruit? Also, would it be possible to post a picture?

Chris and Suze,

Thanks for your help. I checked out the Tomato Problem Solver 2 posting and found a pretty good match in the ripe fruit section: Early Blight. The convincer was the mentioning of attack on green fruit. I somehow thought that Early Blight was a foliar disease only. Live and learn. (And thanks to Earl for the posting the solver). Garaj