Brown Needles Common on Conifers This Spring
Many of the evergreens, especially pines, are not very green this spring. Some have turned completely brown, while others are showing needles with brown tips and green bases.
Symptoms cover a wide range. In some cases, almost the whole tree is brown or it's brown just on one side of the tree. On spruce trees, it might only be the needles that are underneath the branches that are affected, but not those on top of the branches. Sometimes just the needle tip is damaged but the rest of the needle is mostly green.
The reason that the symptoms are so varied is that the potential causes are so diverse:
A traditional example of winter injury is when needles above the snow pack are brown, while those below the snow pack are green.
Another cause is when sunny, warm days in late winter or early spring coincide with frozen soil. During this time, the trees lose water through their needles but can’t replace it because the ground is frozen. Tissues then dry and die.
In other instances, the warm weather may cause trees to deharden too early. Then, when cold weather returns, some trees can’t reharden quickly enough, so the needles die.
Tree health during the previous summer also affects a tree’s response to winter extremes. For example, aphid or mite damage might not be noticed during the summer but shows up the following spring.
Lack of insulating snow cover can cause damage to the root system of a tree.
Nothing can be done directly to fix trees that are suffering from winter injury. The only thing to do is minimize the stresses that the trees face during the upcoming growing season. Also, just because needles were killed doesn’t necessarily mean that the tree is dead because the buds still may be alive.
While environmental damage, such as winter injury are likely causes, insect and disease issues also may be playing a part. Pines may be affected by pine needle scale, pine moths, diplodia tip blight or some other pest. Diseases of spruce trees include cytospora canker or one of the needlecasts. More information on pest problems is available in the “Insect and Disease Management Guide for Woody Plants in North Dakota."
Several items are important to remember when treating trees. Make sure that the correct insect or disease is being treated. If you don’t, the treatment is a waste of time and money. Timing is critical because applying a treatment at the wrong time will not work and is a waste. Always follow all label directions when applying pesticides.