What's Wrong with My Evergreens?

By Dave Zeldon and Ely Schweyer

This is a question we hear daily during the spring, summer and, especially, the fall. Unfortunately, many homeowners do not see any adverse changes occurring in their trees until they look dead, or nearly so.

You Might Not Need to Panic Yet

The discolouration and dropping of evergreen needles are a natural phenomenon and the main cause of needle loss in the wild. Evergreen needles, as the name implies, survive for a lengthy period, and in fact usually have a life span of five to seven years on healthy trees, however, they must be shed. The needles first start to die in the central and lower part of the tree, and this change progresses upward over time. You will see spruce trees naturally lose needles as they get older.

   Age is an important factor here in causing needle loss and branch death, however, in landscape plantings of coniferous evergreen trees, pests and disease are likely the major cause of needle loss and dying branches. If there is a sudden fall of a very large number of brown needles and leaves, this signals to us that there is something drastically wrong!

   This can happen as early as a year or two after a tree is planted. This is especially true in Haldimand and Eastern Norfolk County where heavy clay soils predominate. Spruce trees, for example, do not grow well on clay soils.

When You DO Need to Worry

Here are some of the more common problems, apart from natural aging that afflict spruce trees, the probable causes and ways of treating the problem.

☝️Unfortunately, these majestic trees, the most popular evergreen planted on our residential properties, incur many other pest and disease problems not dealt with here.

Symptom: Rusty brown needles that eventually fall.

Likely causes:

1. Internal fungus disease (called Cytospora or white blister canker). This creates cracks in the bark causing resin to drip and leave grey-white dripping streaks on the bark. The fungus also causes open wounds or blisters on tops of branches. These wounds can be greyish white or greyish blue in colour, eventually turning brown and black.

2. Feeding by spider mites which leave fine, poorly formed webs in the needles, especially near the ends of the twigs.

Best treatments:

1. Properly aerate and fertilize tree out to a distance of half its height in all directions, where possible.

2. Pressure wash thoroughly once a month with water only, all needles and branches as high as possible on the tree. Water pressure dislodges spider mites.

Symptom: Chewed up ends of twigs in June.

Likely cause:

Spruce bud worms which develop in the needle cluster that arises from a bud.

Best treatment:

Spray the biological pesticide, BTK (eg. Dipel), onto the entire tree when feeding is first noticed in early spring, to kill the young caterpillars.

Symptom: Black sooty mold covering twigs and needles.

Likely causes:

1. Spruce bud scales, ball-shaped insects, initially light brown in colour but eventually turning black. Often two to five scale balls cluster in one location on the twig; honey dew excretions from scales become infected with sooty mold.

2. An overhanging shade tree such as oak, maple or elm may have heavily infested leaves with aphids whose honey dew secretions become infected with sooty mold.

Best treatment:

1. Pressure wash tree using water only to dislodge young scales (called nymphs) in May and early June while they are in the crawling stage. Scale nymphs fall to the ground where they cease to be a threat to the tree.

2. Spray shade tree in early spring with insecticidal soap to control aphids. The problems of other coniferous evergreens such as pines, firs, cedars and junipers can usually be treated with correct diagnosis, though some diseases are lethal.

We hope these help you troubleshoot common issues often found in evergreen trees! For more information - and evergreens – visit Eising Greenhouse and Garden Centre! 🌲