This guide groups the common maple problems by what you can see, so you can start from the symptom in front of you. Each section covers the usual cause, how to check it and whether it needs action.

Table of Contents

The short answer: most maple problems people notice are leaf problems, and most leaf problems on maples are cosmetic. Black tar-like spots, brown blotches along the veins after a wet spring and crispy edges in a hot summer rarely kill a tree. The problems worth worrying about show up in the wood and the roots: wilting on one side, a crown that gets thinner every year, a trunk with no flare at the base, or bark that oozes and cracks.

Start here: match the symptom

What you see	Likely cause	How serious
Raised black spots on leaves in late summer	Tar spot	Cosmetic
Brown or purple blotches along the veins in spring	Anthracnose	Usually minor
Brown, crispy leaf edges in hot weather	Leaf scorch	Stress, fix the watering
Wilting on one branch or one side	Verticillium wilt	Serious
Thin crown, small leaves, early fall color	Girdling roots or root stress	Serious over several years
Few or no leaves in spring	Frost, drought or root problems	Depends, test the twigs
Oozing, cracked or sunken bark	Canker or injury	Have it checked

Black spots on the leaves: tar spot

Maple leaves covered in small tar spot lesions — Photo: Teemu Mäki, CC BY-SA 3.0, via Wikimedia Commons

Raised, shiny black spots that look like drops of tar are almost always tar spot, a fungal disease caused by Rhytisma species. The spots start as small yellowish patches in early summer and turn black by mid to late summer. On Norway maple they can merge into blotches more than an inch across.

It looks dramatic, but extension specialists at UConn and the University of Wisconsin describe tar spot as mainly cosmetic. Heavy infections can make leaves drop a little early, late in the season, after the tree has done most of its growing. Spraying a large tree is rarely worth it because full coverage is hard to get.

What helps is cleanup. Rake the fallen leaves in autumn and bag, bury or hot-compost them. The fungus survives the winter on those leaves and sends spores up to the new leaves in spring. For a closer look at the different kinds of spots, see what the black spots on maple leaves mean.

Brown blotches along the veins: anthracnose

Anthracnose is a group of leaf fungi that do well in cool, wet springs. On sugar maple it shows as large brown patches along and between the veins. On Norway maple it often appears as narrow purplish streaks that follow the veins. Badly affected leaves may fall in early summer.

Penn State Extension notes that the damage is usually minor and that treatment is generally not needed on landscape trees. A healthy maple will often push out a second set of leaves. Rake up and remove fallen leaves, prune out dead twigs and avoid sprinklers that wet the canopy. Keep a closer eye on young or newly planted trees that lose most of their leaves two years in a row.

Crispy brown edges in summer: leaf scorch

When leaf edges turn brown and dry during hot, dry or windy weather, the usual cause is scorch. The leaves are losing water faster than the roots can replace it. Scorch is not a disease, but it is a sign of stress, and it is most common on young trees, trees surrounded by paving and trees with damaged roots.

Water deeply and slowly over the root zone during dry spells, roughly once a week rather than a little every day. Keep 2 to 3 inches of mulch over the roots, pulled back from the trunk. On red maple, browning that starts on individual branches in mid to late July, with a dark band and a yellow edge between the brown and green tissue, may be bacterial leaf scorch instead. That disease is spread by leafhoppers and has no cure, so it is worth getting a sample identified.

Wilting on one side: verticillium wilt

Verticillium wilt is one of the more serious maple diseases. The fungus lives in the soil, enters through the roots and blocks the wood that carries water. The classic sign is wilting, yellowing or scorched leaves on one branch or one side of the tree, often in July and August, while the rest of the canopy looks normal.

To check, cut a wilting branch and look at the cut end or peel back the bark. Infected maple wood usually shows greenish to dark streaks. There is no cure, and fungicides do not help. A tree can live for years with steady care: water during drought, go easy on nitrogen fertilizer and prune out dead limbs. If a maple dies of verticillium wilt, replant with a resistant tree such as an oak, a birch, a honeylocust or a conifer. More on this in why maple leaves wilt.

A thin crown and early fall color: girdling roots

If a maple has been thinning at the top for several years, with small leaves, early fall color and dead twigs, look at the base of the trunk. A healthy tree flares out where it meets the ground. A trunk that goes straight into the soil like a telephone pole, or a root that wraps around the trunk, points to stem girdling roots. The University of Maryland Extension lists red and sugar maples among the trees most prone to them.

Girdling roots slowly squeeze the trunk and cut off the flow of water and sugars, and affected trees tend to decline over five to ten years. Small circling roots can often be cut away. Roots more than about two inches thick, or roots that have grown into the trunk, should be assessed by a certified arborist before anything is cut. If you are unsure whether a declining tree is still alive, start with how to tell if a maple is dead.

Leaves late in spring

Maple buds opening in early spring — Photo: Famartin, CC BY-SA 4.0, via Wikimedia Commons

A maple that is still bare when others nearby have leafed out is not necessarily dead. Late frost, a dry summer the year before, winter damage and root problems can all delay bud break. Try a scratch test: scrape a small patch of bark on a twig with your thumbnail. Green, moist tissue underneath means that twig is alive. Brown and brittle means it is dead. Give the tree a few weeks past its usual date before you prune anything out. The full checklist is in why a maple is not leafing out.

Bark that oozes, cracks or peels

Sap or dark fluid running down the trunk can come from a canker, an old wound or an insect. Penn State describes bleeding canker on maple as reddish-brown sap seeping from sunken bark, with wilting and dieback above it. Long vertical cracks on the south or west side of a young trunk are usually frost cracks or sunscald. Neat rows of small holes are the work of sapsuckers, a type of woodpecker. Damage at the base is very often from mowers and string trimmers, so a ring of mulch that keeps them away is cheap protection. See also why a maple drips sap.

When to call a certified arborist

Wilting or dieback on a large tree, especially if it spreads from year to year.
A crown that keeps thinning and no visible root flare at the base.
Cracks, sunken bark, oozing or mushrooms on the trunk or at the base.
Dead limbs over the house, the driveway or a play area.

The International Society of Arboriculture runs a Find an Arborist directory for certified arborists near you. Your county extension office can often identify a leaf or twig sample as well.

Sources

Maple Diseases, Penn State Extension
Tar Spot of Maple, UConn Home and Garden Education Center
Tar Spot, University of Wisconsin Extension
Maple Anthracnose, UMass Amherst
Maple: leaves brown, University of Minnesota Extension
Girdling Roots, University of Maryland Extension

Top photo: Rhododendrites, CC BY-SA 4.0, via Wikimedia Commons

What’s Wrong With My Maple Tree? A Symptom-by-Symptom Guide