Tree Diseases

Tar Spot (Maple)

Tar spot - Tree disease

Fungus Damage

Leaves will have orange to yellow spots earlier in the year.  The spots will typically turn to a darker brown or black later in the summer or fall.  Many fungi are not life threatening, but should be addressed. The fungus will interrupt photosynthesis and weaken the tree.  Trees suffering from a foliage fungus will often lose their leaves in late summer to early fall.


Chlorosis (Nutrient deficiency)

Chlorosis is caused by a deficiency of an essential nutrient or nutrients.  A tree suffering from chlorosis will have yellow in the margins of the leaves gradually getting greener towards the veins of the leaf.  The tree is usually lacking iron or manganese. These elements are just two of the 14 mineral nutrients that trees need.  This is an issue that must be addressed, or the tree will fall into decline and eventually die. There are many treatments that work well for chlorosis depending on soil conditions and species of tree.

Needle Cast (fungus)

Needle cast on spruce

This disease is caused by the fungus Rhizosphaera kalkhoffii and is probably the most common needle disease found in Michigan.  Blue spruce Picea pungens is highly susceptible to this disease.  Blue spruce in southeastern Michigan have seen a decline in recent years.  Poor soil conditions, improper planting, the spread of needle cast and tip blight have greatly reduced the overall health of the blue spruce population.  If you have planted a Colorado blue spruce in the past few years, I highly recommend a tree care plan (soil amendments, deep root fertilization, fungicides) to ensure tree health.

Shelf or Bracket fungi

Shelf Fungus or mushroom

A mushroom or “fruiting body” growing from a tree is a sign of decay.  Mushrooms or shelf fungus are considered decomposers.  They feed off dead decaying organic materials.  When you see a fruiting body of a fungus, decay is present.  It may not be visible, but it is present. The decay can weaken a tree and may cause a hazard.

Blue Spruce Decline

blue spruce decline small 2

Blue spruce in decline

Blue spruce (Picea pungens) decline is the result of many different factors.  Southeastern Michigan has poor soil conditions for Colorado blue spruce. A tree that is planted improperly in poor soil conditions will succumb to disease and insects.  Treatment programs can ensure good health of tree.


Hackberry nipple gall

Hackberry nipple gall

Galls are a plant or trees reaction to damage cause by an insect, or in some cases a much smaller pathogen such as a fungus or bacteria.  The abnormal growth is a reaction to an insect piercing the leaf or larva living within the leaf or stem.  Galls are usually unsightly growths on a tree, but are usually not a severe health threat.

Compacted soil with chlorosis (OAK)

Compacted clay soils and decline of oak

Compacted soils can slowly decrease the overall health of a tree.  A majority of the trees roots are located in the top 12 inches of soil.  If the soil is compressed and is not very permeable (clay soils), the roots will have great difficulty growing and absorbing nutrients.  Also, clay soils do not allow essential nutrients to be absorbed by the roots which compounds the problem.

Black Knot.


Black knot is a common and often serious disease of plum trees in Michigan. Once established, the disease becomes progressively more severe each year unless control measures are taken. Infected limbs will eventually die . Black knot is occasionally found on peach and cherry trees.