Blue and Norway Spruces are susceptible to a branch killing disease called Cytospora Canker. Cankers are dead, sunken areas of bark and underlying wood that form on the lower branches, eventually making its way towards the top of the tree. Resin flows out of the cankers and may drip down on lower branches.

Cytospora can infect branches through wounds and branch stubs, but does not actively develop a Cytospora canker unless the tree is stressed by drought. Small fungal structures, in which thousands of spores form, develop in the canker. However, during wet weather, the spores ooze out in long yellowish threads. Rain splashes the spores to other branches and branch killing proceeds up the tree.

Cytospora Canker 1
Resin Oozes from Cankers on branch


  • Select the planting site carefully, avoiding drought prone sites.
  • Prune out and destroy infected branches, disinfecting the tools between cuts.
  • Cytospora Canker enters a tree through wounds. Therefore, avoid damage to the bark from lawn mowers, tools, etc.
Cytospora Canker 2
Lower Limbs beginning to die off