Question
I have a pear tree of indeterminate age that has developed a yellowish type fungus on the bark. last year it bore lots of fruit but this year there does not appear to be any fruit growing. I have a fig tree with much the same type of deseaseyd

Answer
Elizabeth:
This yellow fungus may represent one of many types of fungal organisms that cause decay within trees.  This is often a slow, yet progressive decline and these "fruiting bodies" may take years before they pop out the side of a tree.  Many often take on the shape of a "shelf", thus they are often called shelf fungi or conks.  If possible, can you send me a photo of this structure on the bark and I will have a look.  Unfortunately, there is no magic bullet for these things, only preventive measures that can help.  After that, good fertilization practices and good watering schedules to help reduce stress may prolong the tree health.

Anyway, if possible send along a photo and I will be happy to have a look and may be able to tell you more.

Regards
Steve