Sugar Maple Sick? 7 Signs Something's Off With Your Sugar Maple

If you have a sugar maple tree in your front or backyard and it looks a little worse for wear, there’s a chance it might be sick. Maples have the proclivity to contract several diseases. Some are worse than others, and some may spell the end for your maple.

Keep reading to discover the signs of sickness in sugar maples, the types of diseases sugar maples can get, and how to fix your sugar maple’s sickness.

7 Signs Your Sugar Maple Is Sick

Healthy sugar maples should have lively-looking five-pointed leaves that are green most months of the year and red, yellow, or orange in the fall. They may also have helicopter seeds and flowers.

Leaf Spots

Leaf spots are both a disease and a symptom that sugar maples may undergo. Depending on the color, location, size, and shape of the leaf spot, it may indicate different diseases — and leaf spots come from fungal, criteria, and viral plant diseases. External forces like insects, nematodes, and herbicides can also cause leaf spots.

Anthracnose leaf spots have a large, irregular size, though there’s a sort of “V” shape to the spot. The area of discoloration is usually tan.

Other times, leaf spots may have a black or purple appearance (known as a “frog eye” symptom). This disease comes from a fungus in the Phyllosticta or Didymosporina gena. Frog eye spots sometimes have black fruiting bodies on the surface of the spot too.

Leaf spots may also be tar spots, which is a fungus growth that turns the spot from yellow to shiny black. Tar spots will cause premature fall coloration as well.

Diseases this symptom might indicate: Anthracnose, tar spots, or Didymosporina genus of fungi.

Cankers

Like leaf spots, cankers are a type of disease affecting many types of shrubs, trees, and plants. Cankers may resemble a “gash” in a tree branch and often are tangentially related to a wound infected by fungus or bacteria. If your sugar maple’s branches have cankers on them, they will weaken your plant considerably. You may notice these cankers when your sugar maple “bleeds” a dark brown sap.

Diseases this symptom might indicate: Anthracnose, a group of fungal diseases affecting all types of maple trees with dark lesions and cankers.

Powdery Appearance

If your usually-green sugar maple leaves develop a “dirty” appearance with white, gray, or blueish powder on them, it’s a good bet that your tree is sick. If you don’t see the powdery appearance on all the leaves but your sugar maple has changed to its fall colors long before it usually does, that’s another sign it’s suffering from the same disease: powdery mildew.

Diseases this symptom might indicate: Powdery mildew. Based on research, the disease tends to develop on trees later in the growing season.

Blighted Leaves

Most commonly, Phomopsis obscurans fungus causes leaf blight. However, the type of blight will depend on the fungus infecting a tree. Fungi from the Aureobasidium, Discula, and Kabatiella gena will often cause anthracnose.

Leaf blight differs from leaf scorch and leaf spots in a few ways. First, leaf blight makes affected leaves look browned in irregular lesions or “streaks” that can touch each other. The lesions may have a yellow ring around them, making them look water-soaked. Blight will attack leaves, stems, roots, and stalks.

Diseases this symptom might indicate: Anthracnose. Leaf blight tends to cause the most destruction in older trees during the late summer.

Wilting

Like all plants, sugar maples are prone to wilting during specific weather conditions. In sugar maples, wilting looks like yellowing or dropping limbs or parts of the canopy. This is also known as “flagging” in some arboreal circles. While parts of the canopy, typically at the top, look wilted, the infection has actually begun underground in the roots. As wilting becomes more widespread through the tree, the sugar maple will lose its canopy and begin to have undersized and off-color leaves.

Sugar maple wilting may startle you, as its onset can be sudden. It usually doesn’t affect the entire tree at once; only one branch or area of the crown will wilt at a time — giving you a chance to catch the disease before it spreads.

Diseases this symptom might indicate: Verticillium wilt, which occurs in the middle of summer when there’s an extended period of hot and dry weather.

Curled or Cupped Leaves

If your sugar maple is struggling in the middle or late summer months, your first indication might be curled or cupped leaves. Pair it with regional droughts or general heat stress and you can bet your sugar maple is sick, most likely with scorch.

These curled, cupped leaves tend to develop brown or necrotic edges, continue to curl until shriveled, and drop much earlier than they would during a normal life cycle.

Diseases this symptom might indicate: Scorch, which affects under-watered or under-fertilized trees during periods of extreme heat.

Stained Trunk or Transparent Crown

Most of the time, you won’t see the inside of your tree’s trunk. You can cut into the trunk, but that will negatively affect the tree’s health. Instead, the backup option to check for internal damage is to analyze the tree’s external health. If your sugar maple’s upper canopy looks thin, small, or is gone altogether during the normal spring and early fall months, there’s a chance something’s wrong inside. You may want to consult a plant pathologist or landscaper in your area to confirm the suspicion.

Diseases this symptom might indicate: Sapstreak, which is a disastrous disease for sugar maples. It will infect trees through wounds in their roots or trunk scars.

How to Mitigate Sugar Maple Sicknesses

Prevention is the best tool a gardener has to protect their sugar maple from disease.

Several of the diseases that affect sugar maples are fungal-based. As such, it’s imperative to keep the ground around your sugar maple tree free of rotting leaves. During the late autumn months, take care in raking your yard of loose leaves. This way, you’ll reduce the number of spores attempting to infect new leaf growth in the spring. It also avoids fungal growth in the wintry weather under a carpet of snow that can seep into the ground and infect roots.

Fungicides will help to solve problems with leaf and tar spots. However, you should discover if leaf spots are your tree’s only issue or if there’s a deeper problem before choosing a fungicide to use.

Canker diseases and sapstreak also come from root or branch injuries opening the tree to infection. When working around your sugar maple, consider how you’re interacting around it, and be careful to place your shovel, hoe, and other garden tools in the soil around it gently. If you do injure a tree’s roots, branches, or trunk, provide adequate nutrients so it’s able to heal itself and fight infection.

Finally, follow the proper care instructions to provide the right nutrients for your sugar maple. While scorch is unavoidable, owners who care for their sugar maple’s needs can mitigate most risks even during drought periods.

Keeping Your Sugar Maple Healthy

As with most plants, daily or weekly checks can ensure your tree’s optimal health. Unfortunately, it’s almost impossible to protect your sugar maple from every virus, bacteria, and fungus that wants to grow on it. Ensure it has slightly acidic soil, a large area to grow, good levels of nutrients and fertilizer, and enough water. If you see one of the seven signs above, try some of the alternatives mentioned above or consider contacting your local landscaper to take the best next step.