Oh, when I look out my living room window I see a Colorado blue spruce that tells a tale. The spruce today is over 25 feet in height but when I bought it this little spruce was only 5 feet. As a matter of fact, I was only 1 ½ inches taller than the evergreen and my children were 5. I can still see my little ones outside with me digging the hole for the spruce. That first Christmas, my family could be found outside decorating this little tree. This ceremony still happens the first of December when my child come back home to visit.
While you may not have a tree in your landscape that invokes such emotion, I do not know how I would handle it if I lost this beloved evergreen to plant disease. In doing so, I have listed the common plant diseases that spruces can suffer from and as of today, there are two new ones to add to the list.
In the past, the spruce evergreen was pretty much disease free. One plant disease that spruce are known to get is Cytospora canker. This plant disease is one that requires some type of damage to enter the evergreen. The signs of this plant disease start off with a sunken area in the bark of a branch located on the lower part of the evergreen. This area can be dripping with resin. This sunken area will end up girdling the branch and the branch will die. This will continue up the evergreen until the spruce is dead.
While this fungus hits when the evergreen is wounded, there are other times when this fungus will take hold and that is during a drought. The prevention strategy is two-fold. First, check out the available soil moisture of the area you would like to plant your spruce in. Make sure that it is not too wet but able to hold enough moisture that will satisfy the needs of a tree that is 50 to 60 feet in height. Second, avoid damaging the branches of the tree but if you happen to nick it and develop this problem, remove the disease branches as soon as you can.
The second common plant disease is the needle rust. This disease affects needles that are year old. The affected needles will turn a rust color and will fall off in the spring.
If you find this in your spruces, the best approach is to simply remove the affected trees.
A few years ago, I would stop here but as luck would have it two new plant diseases have seemed to develop a taste for the spruce. This includes the rhizosphaera needlecast and stigma needle blight.
The rhizosphaera needlecast affects needles that are a year old just like needle rust but instead of the needles turning rust color, the needles affected with this plant disease turn a lavender color. If you turn the needle over, you will find tiny black fruiting bodies that line up in a row on either side of the midvein. The needles affected will fall off, which will create large holes in the tree.
To prevent this plant disease, the best approach is to plant the trees the correct distance apart. This will allow the branches of the trees to dry out and will allow for better weed control.
While this plant disease can attack any spruce, the blue, and Engelmann spruce are the most likely varieties to be affected. The white spruce does have a limited chance of beginning affected while the Norway spruce is not affected at all.
The stigma needle blight is the second new plant disease of the spruce. This is another plant disease that attacks needles that are a year old. The first sign of this plant disease starts off as the needles turn yellow or brown. The needles that have turned brown will have black spots on the underside of the needles just like rhizosphaera needlecast. Once this happens, the affected needles will fall off the branches. This can continue up the tree until the tree is dead.
The best approach to this plant disease is prevention. This is simply done by planting the spruce the correct distance apart from other plants. . This not only allows air to circulate around the plant material is also reduces the chances that you will need to prune the evergreen to control it. This happens more often than not when people do not consider the “mature” size of the tree verses the size it is when they first put it in the ground. While this spacing may look a little silly in the beginning, it will save you the time of pruning back the tree and causing it to look distorted while exposing it to plant diseases.
To keep the spruce from suffering from environmental stress, consider creating a berm around the tree when you plant it. How do you do this? Well, it is simple. Once you have gotten your tree planted, begin to build up a circular berm around the tree using the soil you removed to plant the tree. Do not build this right up against the truck but instead take it out a bit. Pack it nice and tight to keep the soil from eroding away. Top this berm with mulch. Once this is done, you now have a bowl so that you can water without the water running off, which will help with drought stress and weed control.
Another tool you can use to help your spruce is fertilizer but…. The spruce typically does not require any type of fertilizer program but during times of plant stress a little fertilizer will not hurt and when I say a little I do mean a little. To utilize this technique, add one tablespoon of a 12-12-12 balanced formulation. Yes, I said one tablespoon. Sprinkle the fertilizer around the tree and let Mother Nature water it in. Do not think about jumping the gun and adding some fertilizer into the hole when you plant your tree. This will burn the roots of the tree and damage and/or kill it.
Now that you know the tricks of preventing these old and new plant diseases of the spruce, what are you waiting for? Get out there and plant a spruce in your landscaping. Hopefully, you will be able to create your own family story around a living tree that will stay in your family for the next 50 to 60 years.