MSU Extension

“My tree is dying. Can you tell me what’s killing it”? This is a common question with earnest interest. Unfortunately, it’s usually not precise enough for a credible response. When damaging agents are seen in the forest, it’s a good idea to learn what is happening. Before contacting a resource, first record a few observations and consider taking some photos.

Photos of symptoms and the whole tree can be of great diagnostic use. Be sure that they clearly show the intended issue. A picture of a dead tree won’t be too helpful. It’s quite simple to attach a few images to an email message or bring them into an office. Photos can also help confirm tree species identification. Remember that it can be difficult to identify a person from just a picture of a finger! It’s similar for trees.

Correct tree species identification is critical. In some cases, the genus is good enough but species identification is best. A lot of time can be misspent by chasing-down “pine” diseases when the affected is tree is a spruce.

Next, it is often important to carefully observe which tree parts are damaged. Brown or wilting leaves may be caused by damage to branches, stems, or roots. Leaf spots or holes are typically normal natural events, especially later in the season. Even severe defoliation isn’t necessarily a problem for an otherwise healthy tree.

When leaves are symptomatic, note any patterns. Top down? Bottom up? Inside out? Outside in? Are nearby or area trees of the same species showing symptoms? Is this the first year when the ailment was seen? A bit of sleuthing might reveal a key piece of information.

The timing and seasonality of these patterns can be important, too. Insects and diseases have life cycle patterns where symptoms typically occur at certain times of the year. When did the symptoms first begin? How long has the problem been ongoing? Has the weather been unusual?

The size of a tree can sometimes be important, both height and diameter. Keep in mind that large trees are not necessarily old trees. Open grown trees can grow rapidly.

The habitat can sometimes provide clues. Some diseases have alternate hosts. So, knowing the general soil type, proximity of wetlands, and these sorts of landscape features can be important.  

Of course, residential trees generate a greater proportion of inquiries as these trees are more often seen. Urban environments are particularly harsh for trees – lawns, mechanical wounds, chemicals, soil compaction, open-grown exposure, etc. And tree ID can be more difficult due to the many horticultural varieties available as ornamentals. Homeowners might benefit most by contacting an arborist or urban forester, rather than a field forester.

Especially for residential trees, has the ground been recently disturbed? Cable trenches fill; lawn amendments, over/under watering, driveways, walkways, and any number of home landscaping features can disrupt root systems. Keep in mind that most roots are within the top 18 inches of soil and spread from the trunk to a distance roughly equal to that of the height of a tree.

If you need to provide a sample, be certain to collect one that can help diagnose the ailment. A sprig of dead leaves or needles is not usually helpful. It’s best to collect a sample in the process of dying and attach it to the sort of information earlier described.

Many times, observations of insects are secondary infestations, rather than the original cause of the problem. For example; ants will excavate trunks where wood-rotting fungi have softened the tissue. Or, woodpeckers will seek larvae that have successfully invaded under the bark into the living tree tissues. Sometimes, other insect species that happen to be visible are incorrectly attributed to the damage.

Lichens are sometimes mistaken for a fungus that might hurt a tree. Rather, lichens merely use the tree as a substrate upon which to grow.

Normal aging of trees, especially bark characteristics, can cause concern. Smooth bark often breaks-out into rougher textures as a tree grows. Older bark will slough-off. These changing appearances can be mistaken for an ailment.

When something appears abnormal with trees, it’s a good idea to learn why, Michigan State University Extension webpage is a good place to start. More often than not, the cause poses little permanent harm to the tree. However, early detection of infestations, especially those of exotic species, can lead to effective treatment or eradication. Having many “eyes” in the forest is one of the best ways to protect a forest.

Pictured are the following diseases common in trees, here are some ways to identify them:

1. Anthracnose is a common leaf disease in cool, moist environments.

2. Tar Spot disease is common among maples during mid to late summer.

3. Perennial black knot cankers form on all species of cherries and their allies.

4. Nipple galls from various species of insects and mites are common on many tree species.

5. White waxy coats from beech scale provide access to fatal pathogens of beech.

6. Woolly aphids are common but if seen on fir or hemlock, should be reported.