Sorry for delayed response.

Possibly bacterial wetwood, a common disease of elm.  You may notice the drippy material smells bad.    Is fence rail or PVC tube damaging the trunk?

See also: http://www.ext.colostate.edu/pubs/garden/02910.html

Hi Robert,

Thanks for your response.  It does seem likely that wetwood has affected this tree.  The tree has grown up against the fence pictured.  There are also many boards of wood and other detritus leaned up against and near the trunk (messy neighbor situation).  I read in the info sheet and in other sources that I should clear away anything that may be damaging the trunk and cut off the bark of the tree in the affected area.  Could you advise me on treatment and point me to a picture of a tree with the bark removed in the way I should?

Thanks,
Tim

Tim,
just use a sharp knife to cut away any loose (unattached) bark.   And you might consider fertilizing the elm with a granular lawn-type fertilizer (not one that includes an herbicide).

However, since your elm is a Siberian elm that grew up from a seed, it's important to remember that Siberian elm is a very low-value tree.  Why not just cut this one down and plant a more desirable tree?

Hi Robert,

Thanks for the instructions.  I have a Bayer product that is .74% imidacloprid and .37% clothianidin that I use to control elm leaf beetles.

I think value is very subjective.  The amount of shade this tree provides is very high-value.  I can't do without it, hence my degree of attentiveness to it but I can appreciate your perspective.  

However, I have a spot in the front of my house where I may plant a tree.  What should I consider?  Would you suggest a fruit tree or another elm?

Thanks,
Tim

That depends on soil type, exposure (S side of house?), whether or not the tree will be a in a maintained lawn area, whether you want shade primarily or ornamental features like flowers, fall color, fruit display or edible fruit, whether you want an evergreen or a deciduous tree, etc  Remember that evergreens provide shade all year, not just during the growing season.   Evergreens may shade sidewalks/drivewaysand windows in winter.
There are many possibilities listed at http://www.ext.colostate.edu/pubs/garden/treereclist.pdf   and http://www.ext.colostate.edu/pubs/pubs.html#gard_ts

The site is between the street and the sidewalk, on the East side of the street.  The hell strip there is covered in brick and the soil is probably just Denver standard.

I just wanted to follow up on the chemicals I mentioned for the elm, are they appropriate for the feed/pest control purposes we've touched on?

Yes.   see also: http://www.ext.colostate.edu/pubs/insect/05521.html