blossom end rot

PS -- I saw what *might* have been a leaf footed bug on one of the affected maters this morning. Looked like a black, slightly oversized, armored mosquito.

It is a classic tomato rot called "Blossom End Rot" , BER for short.
You will hear and learn about it .

Ah, crap. Ok. Thanks, hoovb.

Not a problem - very common early in the season. Just keep the watering consistent and the later ones will be fine.

Yeah check all the fruit on the vine and remove any of them showing it and toss them. Reduces demands on the plant and they'd not be edible anyway.

If you want to read more about it there is a FAQ here about it and lots on info on the web.

Dave

Thanks all. I did some reading and I'm guessing the problem is that I've been overwatering the past few days. I wouldn't have guessed that just a few days would have such a big impact, but earlier fruits did not have this problem and the only change is that I've been watering more often.

I've been kind of winging it on watering up to now. That has worked OK for hot peppers in the past, but I gather maters are more sensitive about such things. I guess I'd better go get some dowels.

The good news is that you caught them quickly, and not when the tomatoes were almost full sized.