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Black Spots On Silver Maple Leaves [Causes With Best Cure]

The black spots in Silver Maple tree leaves can make you panic, but calm down, as it is not a deadly issue.

Generally, the fungus Rhytisma acerinum causes Silver Maple to have black spots on its leaves. Breeding conditions like excess moisture, high humidity, and low light condition supports its germination and worsen the case.

However, you can control and cure the fungal infestation by returning the growing condition to its routine. Follow the article to get a thorough insight.

Causes Of Black Spots On Silver Maple Leaves

Black spots, also known as Tar spots, are an unusual fungal disease in Silver Maple (Acer saccharinum) leaves due to Rhytisma acerinum.

Most of the older leaves of the Silver Maple tree become victims faster than younger leaves as they fall under the fungus effect for a longer period.

Moreover, certain growing conditions boost the appearance of black spots on Maple leaves. Some of them are as follows.

1. Excess Moisture

The young Silver Maple tree prefers regular watering to establish. But once the tree reaches maturity, they become moderately drought tolerant.

However, those unaware of the requirement tend to follow the previous routine leading to overwatered Maples.

Such a situation for an extended period triggers the black tar fungus growth as it is a moisture lover. It proliferates rapidly to affect the leaves.
Black spots on Silver Maple leaf
Standing water around the tree creates a favorable environment for fungi.

You can notice small black spots with yellow circles at the beginning that slowly increase in size and cause leaves to fall.

2. Low Light Condition

Like most native trees, Silver Maple loves bright direct sunlight for at least 6 hours for optimum growth.

Moreover, they require proper air circulation around the roots to maintain healthy growth and increase defensive power.

However, low light aided by poor soil creates microscopic conditions suitable for fungal growth and increases the severity of black spots.

The initial symptoms are wrinkled and brittle leaves that start to have yellow rings around black centers. This usually makes the tree appear unhealthy and unsightly.

3. High Humidity

Leaves turning black on Maple trees is solely because of the Rhytisma fungus. But high air moisture is the crucial factor in determining its spread.

Usually, the Silver Maple tree loves a wide range of humidity and is not fussy about it. However, the fungus loves high humidity and moisture lying on the leaves to germinate.

Thus, you can notice the infestation to be highly prevalent during rainy days, which leads to black edges on Maple leaves.

Moreover, the high humidity means prolonged wetness around the Silver Maple, which increases the chances of infection and worsens the situation.

4. Fungal Disease

The causative agent directly responsible for the Silver Maple leaf black spots is Rhytisma acerinum fungus.

They usually appear under favorable damp conditions and indicate their presence with small greenish-yellow spots on the upper surface.

And once the infection continues, the spots turn tar-like black and have chlorotic rings surrounding the spots. The spots measure around half an inch in diameter.

Although the disease does not pose a severe threat, it can still hamper the tree’s health and cause the early fall of leaves.

How Do You Treat Black Spots On Maple Leaves?

Correcting the growing situation always works best for the Silver Maple tree and can be fruitful for tar spot treatment.

Thus, follow the given checklist of measures. You can do these immediately to take control of the fungus and eliminate it.

  • Stop watering the tree as soon as you notice soggy and damp soil. Allow the excess moisture to dry out before watering it again.
  • Boost drainage and aeration by breaking up the compact soil around the tree base.
  • Wipe up any moisture present on the leaf.
  • Trim the damaged leaf and dispose of it somewhere safe so the tar fungus does not spread its spore.
  • Collect the fallen leaves and burn or throw them away as they might hold the fungus’s spores that can overwinter and return next year.
The fallen leaves of Maple tree
Collect the fallen leaves before the late fall to avoid overwintering of fungus.
  • Maple leaf black spot does not need a chemical approach as you can easily control it from optimum cultural practices.
  • However, you can use a copper-based fungicide which is good for Maple tar spot. Also, you can use Bordeaux mix to spray on tree fungus.
  • Floor the tree base with reflecting surfaces like light-color mulch or stones that can redirect the sun ray and increase the light availability.

Prevention Measures Of Black Spots On Silver Maple Tree

Good sanitary practice is the key solution to most problems related to fungal diseases.

However, you can further save yourself from all the trouble by maintaining the growing schedule and need from the beginning.

  • Provide 6 hours of sunlight to direct light-tolerant varieties of Silver Maple like Beni Maiko, De Shojo, and Ao Shidare.
  • Prune off the dense foliage of Maple trees in fall to allow light penetration and improve soil aeration.
  • Maintain a temperature of 65-80ºF for ideal growth. They can also tolerate cold temperatures up to 5ºF.
  • The tree loves a well-draining, slightly acidic soil (4.5-7 pH) rich in humus.
  • Collect the leaves as soon as it falls on the ground and use them for composting.
  • However, avoid using the compost in Maple trees if you are composting the diseased leaves, as the fungus only infects them.
  • Boost the immunity of trees by fertilizing with a slow-release once every spring, summer, and fall.
  • Maintain plant health by treating with neem oil and insecticidal soap to control pests like aphids, maple scale, and sapsuckers.

From Editorial Team

Additional Information!

The Silver Maple tree is a native of North America that has extended its root to Eurasia and Canada. It is famous for its silvery-green leaves that turn bright yellow in fall.

Meanwhile, the tree is a popular choice for landscaping and shade that tolerate a wide range of growing conditions.

But are susceptible to fungal attacks. So watch out for them!