Spotting mites, aphids

Spruce trees have few insect or disease problems except for spider mites and aphids. Both are tiny insects that suck the juice from plant leaves. The needles die and then fall off. If the tree starts to die at the top, it can die back for several feet. A strong hose spray of water will help wash the insects away if they are the culprits.

There is a pretty common disease of Colorado and Norway spruces, hemlocks, and Douglas fir called Cytospora canker. It usually affects trees that are older than 15 to 20 years old or taller than 20 feet. The disease usually starts on the lower branches of the tree and progresses upward. The needles first turn purplish, then brown and finally drop, leaving dry, brittle twigs. The fungus enters the tree through wounds. You might see a coating of white resin on infected twigs.

This is a stress-related disease, so trees should be kept mulched and watered well during dry periods. A source of tree stress is associated with planting spruces close together in a group or row where they become intertwined.

If you notice a problem with your evergreens, remove infected branches promptly during dry weather to reduce the spread of the disease. Disinfect your pruning tools between each cut. Unfortunately, there is no chemical control.