Question
Our community planted Cleveland Pear trees along our streets about 5 years ago.  On my property I have 10 trees planted approximately 50' apart.  I live in Maryland, so the weather they see is hot humid summers and cold winters with few significant snow accumulation.  Up until this year all 10 trees were doing well.  Now only 9 of the 10 trees appear to be doing well as the tree directly in front of the house appears to be thin regarding the leaves on the tree.  The leaves appear to be smaller than the other 9 trees, and some of the leafs have brown curled up edges.  I also noticed a few small branches void of any leaves.  Leaves that do not have the curled edges appear to be as green and pliable as the other trees, but somewhat smaller in size.  
All of the trees have mulch around the bottoms extending out about 24" all around.  I keep the "suckers" trimmed down in the mulched areas for all the trees.
Any thought or suggestions?  I am concerned that this tree may have some type of disease.

Answer
Vic:
In Arkansas, we are currently seeing many ornamental pears (Callery) defoliate after the leaves develope a premature fall color (purple and red- then brown). We have been seeing this occur over the last 3-4 yrs- Seems like it is worse during hot/dry weather.  Does this sound like your trees? We have not been able to find a disease organism associated with this decline. Currently we feel that it is an inherent root/graft problem with these trees.  Some trees have stringtrimmer or machinery damage to the bases and some do not. This "decline" is puzzling and has been observed in several surrounding states.

From a disease standpoint, Bacterial Fire Blight is the biggy- at least in my part of the world.  With fire blight, initially the ends of the branches turn dark brown to black at the tips, then spreads inward.  Affected branches usually appear randomly in the crown. FB is the biggest disease problem- caused by a bacteria called Erwinia.

Mulch should be no deeper than 3 inches and scopped away from the tree base few inches.  Mulch up against the tree provides a good habitat for bugs!

Regards
Steve