Colorado Blue Spruce
Colorado blue spruce are a favorite tree of many gardeners. Their bluish green needles and pyramidal shape are a nice addition to the landscape. But several diseases can kill branches and distort their beauty.
One such disease is needle cast. It’s usually not deadly, but it ruins the beauty and screening value the trees provide. Promptly remove and destroy infected branches to help slow the spread of this disease. Disinfect your tools with a one part bleach and nine parts water or 70% alcohol solution between cuts. Make sure your trees receive sufficient water during dry periods, mulch the soil and give them plenty of room for light and air to reach all parts of the plant.
Copper containing fungicides are listed as effective against needle-cast and some formulations are considered organic. Proper timing and thorough coverage are critical for effective control.
A bit more information: One of the other common disease problems on blue spruce is cytospora canker. There is no effective chemical control. Removal of diseased branches, mulching and proper watering can minimize the damage.