Colorado Spruce browning needles
Dear Master Gardener, I have two Colorado spruce in my backyard which I noticed that the needles are browning out recently. My backyard is slightly inclined towards the end with a small depression close to the fences and these spruces are planted around ten feet up away from the depression facing a south western direction. They were planted around 18 years ago. Can you tell me what is the most likely case happening to the spruces by looking at the attached photos? The needles are all brown inside the tree with the outside still green. Many appreciation for your help. I am located in Toronto, southern Ontario, Canada with zone 5. Thanks
Outside United States spruce diseases
There are a number of pathogens that affect Colorado blue spruce, and their incidence seems to be on the increase. Your trees are likely suffering from a fungal disease, but you will need to do some close inspection to identify which one. Identification is needed to determine whether the trees can be treated successfully.
Cytospora canker is common in Colorado blue spruce. The signs include dead buds, with no needles on infected twigs. Infected twigs and branches can occur anywhere on the tree. Lots of pitchy sap can be found at branch unions or cankers. Occasionally, you may find golden spore tendrils coming out of dead twig or cankers. Drought stress is a major factor causing this disease. Management includes minimizing stress by watering, mulching with wood chips, and applying compost every year. Avoid crowding. Avoid wounding branches and trunk. Prune out infected branches only during DRY weather in late fall. Sterilize cutting tool between each cut (otherwise, you spread the disease.) Fungicides are not effective against this disease. You can read more at: http://extension.umd.edu/hgic/cytospora-canker-spruce
The other group of fungal diseases are called needlecasts. The buds and current years needles are usually alive and green. However, some or most of the older, infected needles turn brown or purple. Later, they fall off. Black fruiting bodies can be found in the stomata. which are normally white (see attached photo.) You may see them using a hand lens. Management involves increasing air circulation in the tree by pruning off lower branches. Apply a fungicide when needles are half elongated in spring, and then again when fully elongated. Two or more years of treatment is necessary.
Due to the increase in diseases, Colorado blue spruces cannot be expected to have long lives. Yours may be at an age where you might consider planting new trees in anticipation of the time when the spruces will need to be removed. I suggest you consider species that are native to southern Ontario since they are generally better able to fend off pests and diseases.