Question
I live in southern California mountains @ 5000ft elevation.Several oak trees have dying leaves & are dropping. The entire tree (trunk & all branches) is covered with spit like clear bubbling substance. It appears to start at the top of the tree & then spreads in & down. It started on one tree & now there 4. Will this spread? The size of the oaks effected are 8-10in. dia.

Answer
There is a disease that is effecting oaks in Calif. that is a major problem. It fits some of the information about your tree. But it could be a condition called slime flux. BUT to make sure i would suggest that you contact the calif Forestry agency and tell them you think you have an oak with Sudden Oak Disease (SOD)and ask them to come take a look. Here is a web link to more information on Sudden Oak Disease. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7498.html

Here is a contact web link about SOD http://www.suddenoakdeath.org/html/county_contacts.html