Question
Bark has started to peel on trunk (not at ground level) and at base of largest limbs just this winter.  Tree is more than 20 yo, produces great oranges.  There is no black fungus or other finding under the bark.  The inside looks healthy. I would hate to lose this tree.  Can you suggeste reasons for this?  Would it help to wrap tape the trunk or these areas?  Thank you, Heidi

Answer
There are several different causes of bark peeling and you will need to do some more investigation and monitoring of the tree to figure out what might be going on.

Sometimes the bark peels as the result of an environmental problem known as sunburn.  Usually this is more common on the southwest side of the tree or where pruning has exposed the trunk, but it really can occur on any side of the trunk without explanation.  Citrus bark is somewhat thin and some growers will paint the trunk with a water based white latex paint to help reflect the sun.  You can also wrap the trunk to help with the problem, but you will probably want to replace the wrap or paint each year due to trunk expansion.

Bark peeling can be caused by various fungal pathogens.  Usually there is oozing or gumming associated with the peeling and the bark may crack.  Sometimes the pathogens are active in the root system so you will not see obvious symptoms until much damage below ground has been done.  I would recommend that you excavate some of the roots to see if they appear healthy.  A healthy root system will have firm roots and many small lateral roots.  Roots that are not healthy will often be dark in color and the outer layer may fall off easily.  Secondary roots may be few.  Root rot problems are difficult to control.  Avoid over irrigation and improve drainage round the tree.  

Hopefully you will find that the roots appear healthy and no further problems develop.  Good luck!