Black Spots on Maple Leaves

Maple trees are a sight to be seen, and its leaves are one of the most recognizable shapes in all of nature. As fall rolls around, the bright green maple leaves will slowly change colors, from yellow to bright orange and finally red, before falling off the branches. It is a fantastic natural transformation. 

Maple trees in your yard can provide shade and protection and improve the aesthetics and curb appeal of your home. Unfortunately, those beautiful leaves can suddenly sport ghastly brown marks, called tar spots, especially in areas with heavy rainfall. 

Our team of experts at YardSmart put together a short guide on dealing with tar spots on maple leaves. If you would like to know more about how you can restore that vintage maple tree look, read on. 

What Are Tar Spots?

Why are there brown or black spots on my maple leaves? Tar spots are a fungal disease that affects maple trees worldwide. Although the appearance of the leaves and the tree might trigger some panic alarms, we assure you that tar spots are harmless to the long-term health of your tree. They negatively impact the aesthetics of maple trees and their leaves and could cause the maple tree to lose its leaves prematurely. 

Several types of fungi can cause tar spots in maple trees, and the following maple trees are most prone to tar spots:

  • Oregon maple
  • Norway maple
  • Silver maple
  • Red maple
  • Sugar maple
  • Box elder
  • Sycamore

The tar spots begin as pale, yellow spots, and intensify as summer progresses. A small, black spot appears in the middle of the yellow spot, growing into a large, black spot that looks as if tar was spilled on the leaf. If the tree is left untreated and leaves are not removed immediately, the spores from the infected leaves can travel in the wind and germinate, penetrate new leaf tissue, and begin a new disease cycle. 

When Do Tar Spots Appear?

Tar spots are a fungal disease and prefer moist climates with plenty of rainfall. The most common time of the year for tar spots to occur is in late spring, early- to mid-June being the optimal time when fungi flourish. 

Initially, the tar spots will appear small and harmless with a light green coloration. As August rolls around, the spots will grow larger and start to change color. Tar spots do not cause long-term health effects to maple trees, although it does affect their appearance and can lead to leaves falling off the tree early.

How Can I Get Rid of Tar Spots?

There are several steps to follow to ensure the tar spots on your maple tree will not reoccur next spring. 

Quickly Dispose of Fallen Leaves

Make sure to get rid of the fallen leaves next to your trees as soon as possible. Due to the fungal nature of the disease, it can quickly spread from the infected leaves onto new spring foliage. As soon as the leaves hit the ground, collect them and either burn them or bury them somewhere away from the yard. Another alternative is to compost them if you are keen on sustainable and organic gardening. 

Do not wait for the leaves to pile up over several weeks because it could be too late to stop the spread to new spring foliage. Get in the habit of collecting the fallen leaves every few days. 

Treating the Maple Leaves with Fungicides

In case you have a serial problem with tar spots, and they keep reoccurring every summer, it might be time to take a different course of action. Fungicides are a quick and efficient way to deal with different types of fungi, including those that cause tar spots in maple leaves. It is best to consult a professional arborist to determine which product is ideal for your maple trees and leaves. 

The process requires a lot of precision, and we do not recommend it as a DIY project. If your maple trees are still young and give modest foliage, you will most likely be able to treat the tree on your own. Just be precise and go slow to ensure you cover all of the leaves with the fungicide adequately.

For fungicides to be 100% effective, you have to cover all the leaves on the tree and prevent those fungi spores from reaching healthy foliage. You need to treat your tree with fungicides at least three times when you begin seeing the unsightly marks on your maple leaves. 

Complete the first spraying as soon as you see the tiny buds appear on the maple leaves. After the first treatment, allow anywhere between 7 and 14 days before respraying the leaves. 

If you have several maple trees, and they are fully-grown, we recommend hiring a professional arborist to take care of the trees for you. An arborist will take much less time, prevent you from having unnecessary headaches, and restore the appearance of your tree while eradicating the tar spots from your maple leaves.

Tar spots are a fungal disease and prefer moist climates with plenty of rainfall

How to Prevent Tar Spots from Reappearing

You managed to get rid of the tar spots, keeping the foliage of your maple trees healthy and looking beautiful. But tar spots are notorious for being a reoccurring disease, especially in areas susceptible to heavy rainfall. Prevention should be your primary focus to eliminate tar spots in the future. 

Because fungi thrive in moist soil and climate, make sure not to overwater your maple trees. Anywhere between 4 and 6 inches of soil should be wet when you water, and anything over that amount is unnecessary and counterproductive. Always wait for the soil to thoroughly dry before rewatering the trees. 

The second step you can take to ensure tar spots do not reappear is to provide your maple trees with plenty of air circulation and sunlight by regularly pruning them. Pruning your maple trees once a year should do the trick. 

Occasionally test the quality of the soil of your maple trees. The soil has to be rich in minerals and provide nourishment to the trees for them to stay healthy and avoid disease. If you find that the soil has lost much of its nutrients, purchase adequate fertilizer and add it to your soil. After a few weeks, retest the soil to confirm the trees are getting the right nutrients. 

Even if you think that everything is good with your trees and soil, you should have a professional arborist assess your maple trees every once in a while. They are experts and know what clues to look for and can identify signs of potential problems with your trees, providing you with sound advice on how to ensure a long and healthy life of your maple trees. 

If you need expert help dealing with tar spots on your maple leaves, do not hesitate to contact YardSmart. We are a locally-owned and operated lawn care and snow removal company with more than 40 years of experience servicing residential and commercial properties in the Greater Toronto Area. 

Our team has plenty of experience solving all lawn and yard care problems. Call us and schedule a free consultation and receive a free estimate. Let us bring those maple leaves back to life and make your yard look pristine.

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