Is this infected, a scab, or necrosis? Should I do anything different? (Photo)

Unfortunately sometimes after surgery there can be some skin loss.  This is common under the breast.  The open area will heal secondarily with the application of Bacitracin.  Generally the scar will fade and improve.  It can take several weeks.

Based on the picture alone, you appear to have an isolated area on non healing/ischemic tissue.  Breast reductions do have the potential for wound healing issues especially near the location where your picture shows such.  I would encourage you to be patient with the healing process.  I would get direction from your surgeon as to how they recommend caring for areas with poor wound healing.  

Best wishes for a speedy recovery,

Dr. Mooty

Congratulations on your breast reduction, daniclevi!
It looks to me like that part failed to heal properly. Simply continue what you’re doing and that area will heal in a few weeks’ time.
And if you have any more concerns, best to visit your reputable and board-certified plastic surgeon so that he can also monitor your recovery.
Best of luck!