Not a disease. Some toms do that more than others. In my garden, direct sun exposure onto the shoulders seems to accentuate on some.

Perhaps Carolyn will come along to explain the details.

jean001,

Thanks for the reply.

This has been going on for a few years and I was getting to the point of forgetting tomatoes this year. But if it is not a disease I will try it again.

This is a portion of my reply to dirtdog: I do get a lot of sun but not that many hours per day. Full sun from ~11:30 AM to ~3:30 PM.

Not a heavy pruner, only a few bottom branches to keep off the ground.

Yes, I have found it helps to pick them real early and I mean real early. Some I have picked that I thought were early enough developed the same yellow and eventual rot on my kitchen counter.

Again, thanks for the reply and the information you povided.
---Jerry---