By: Janet Doss, Certified Arborist
As fall approaches, attention is usually given to shade trees. Why? Leaf raking! However, fall is an excellent time to give some attention to the other trees in the yard. The ones that don’t have leaves all over the ground—the evergreens.
Take a break from the rake and go and look at the evergreens. The insect and disease problems as well as the stresses from this year’s weather are there for you to see. But, what is causing the problem? With a little bit of observation, the problem can be identified. Ask yourself a few questions about what you are seeing:
Question 1: What kind of evergreen?
In the south, some evergreens have leaves such as the hollies and magnolias. These are broad-leafed evergreens. In the northern climates, most of the evergreens have needles, so the term evergreen is usually associated with the trees that have needles.
Question 2: What kind of needle?
The traditional arboriculture answer would be either flat or somewhat rounded so that you can roll the needle between your fingers. Ask this question instead: How much pain? Are the needles sharp? Would they hurt or are they soft to the touch? It’s the “painful” ones that seem to have the most problems. These would be the pines, junipers and spruces. The ones soft to the touch tend to have less problems. These would be the yews, arborvitae and firs.
Question 3: If it is a “painful” evergreen, is it a spruce, a pine or a juniper?
Junipers are usually more shrub-like. They come in many shapes but usually are not what would be considered a tree. The spruces and pines are often confused. If the needles are long, it’s probably a pine. If the needles are short, it’s probably a spruce.
Question 4: What are some of the more common problems of the “pain” group?
If it is a spruce with lower branches dying, this would be cytospora canker. This is a fungal disease that girdles branches. If the branches are alive, but losing a lot of needles, this could be a needlecast fungus. Do not confuse this with shading. Spruce trees shaded by other trees will lose their needles, too.
If it is a pine, look at the new growth. Are the tips brown and dry? This could be sphaeropsis, yet another fungus. Now look inside at the trunk of the tree. (Careful, don’t poke your eye!) Are there any globs of sap stuck to the trunk? This is caused by an insect called the Zimmerman pine moth. Its larvae tunnel into the wood.
NOTE: An exception to the above “pain” group is the white pine. They do have long needles, but they are soft.
Question 5: If it is not a “painful” evergreen, is it an arborvitae, a yew or a fir?
Firs are usually confused with spruces. However, fir needles are flat and soft to the touch. There are few firs grown in this area, because the growing conditions are not favorable for them. You will see more in a Christmas tree lot than growing in the landscape.
Yews also have soft needles. These tend to be used as foundation plants and are usually the shrub sheared into geometric shapes. Yews are tough plants with few insect and disease problems.
The third “painless” evergreen, the arborvitae, has needles that do not look like needles. The tips of the needles are rounded rather than flat or pointed. Although arborvitae make a good landscape plant, they do have a couple of pest problems. Look at the needles. Are they speckled or yellow? This is from spider mites. Or are the tips of the needles brown and dead? This is needle miner damage.
One last question: Have the interior needles suddenly turned brown and have they started falling off?
This is seasonal needle drop. This is especially noticeable on white pines and arborvitae. Most people do not know that evergreens do shed their needles. The needles are not green forever.
There are a few things to do this fall to help care for the evergreens: Keep them watered if there is no rain. Evergreens will lose moisture through their needles even in winter. Also spray antidesiccant on newly planted evergreens and other ones susceptible to winter burn such as the arborvitae. If the plants have a fungal disease, sign up now to have these trees treated early next season. Fungal diseases need to be treated early. And, as always, if you have any more questions, you can get help from our Certified Arborists.
© Copyright 2002 – Wachtel Tree Science & Service, Inc.