Known for their conical shape and evergreen needles, Norway spruce trees can be beautiful as long as disease doesn't strike. Just like germs spreading from human to human, disease can spread from tree to tree. To maintain the health of your trees, treat tree diseases as soon as they appear.

Norway spruce is susceptible to a variety of diseases, but the two main ones are cytospora canker disease and Rhizosphaera needle cast. Both diseases occur because of fungus growth on the trees, but each has different symptoms.

When you think your spruce trees have a disease, try to identify it. Yellow or orange-brown spots marring the surface of the trunk can indicate cytospora canker disease. Oozing liquid from bumps that may look like pimples is another symptom. Rhizosphaera needle cast tends to affect the foliage of spruce trees rather than the trunk. When your tree has this disease, you may notice the pine needles turn a purple-brown color in late summer or early autumn. Along with the color change, the tree may shed its needles.

Other diseases can affect spruce trees, including Norway varieties, but they don't occur as frequently as the main two diseases. A professional arborist can evaluate tree diseases and identify whether or not the symptoms match less known ones. If an arborist can't identify the disease, she may take samples for a diagnostic analysis.

Disease often sets in when you fail to take proper care of your trees, and it can infect a tree a year before the symptoms occur. Paying attention to your trees can help you identify the symptoms as soon as possible, improving your chance of saving it. As disease infects your trees, they weaken, allowing the disease to worsen. To prevent stress on your Norway spruce, avoid overwatering it. Keep lawnmowers and weed trimmers a safe distance from trunks to prevent damage from blades. Spraying fungicide on your trees throughout the year may prevent cytospora canker disease and Rhizosphaera needle cast by killing the fungus before it can take root.

When disease does strike, remove as much as the infected area as possible. Peel away dead bark and prune-infected branches. Clean any cuts or exposed areas with fungicide. When you finish, use chlorine bleach to disinfect any tools you worked with to remove the infection. This prevents the spread of the disease.