Seiridium canker  
   
Dead branches Sap oozing from canker
Image depicts dieback symptoms caused by Seiridium canker disease on a Leyland cypress tree. Image depicts resin oozing from a Seiridium canker.
Credit: J. Williams-Woodward, Univ. of Georgia Credit: J. Williams-Woodward, Univ. of Georgia
   
Clemson University Extension Fact Sheet, Leyland Cypress Problems