FAQ

I'm not sure if this is an ornamental pear tree or a fruiting pear tree.
Not knowing all the environmental conditions, the symptoms of leaf fall and
oily sap is not enough information to make a correct diagnosis. If you would
respond with more information including irrigation schedule for tree, age of
tree, any recent (last 2 years) construction within 10 feet of the trees
that might affect the root system would be helpful.  Leaf drop is not
typical for this time of year, so I'm guessing it is related to a watering
issue.

A syndrome known as gummosis is sometimes associated with pear (Pyrus sp.),
but more common with Prunus (peach, apricot, cherry) species.

The gumming or sap flow is a result of mechanical injury, insect damage,
fungal diseases, or improper growing conditions. Sometimes it happens
because too much water or nitrogen fertilizer has been applied.

You should inspect to see that there are no cankers on the trunks of the
trees that might be harboring disease spores. Check to see that there is no
insect activity. Once you've ruled out those two problems. Gummosis is
typically used to refer to gum produced by a tree or shrubs due to
environmental conditions, not due to a pathogen (disease causing organism)