Spots on japanese maple leaves

(Answer)

The leaves of your red maple tree appear to be infected with powdery mildew. Powdery mildew is a common fungal disease characterized by a white, powdery coating on leaves and petioles (leaf stems). The leaves may turn yellow, drop early, or become twisted. The white patches may also develop black spots as the fungus prepares to overwinter. Powdery mildew arises late in the season during warm, humid weather and cool nights. Although the mildew is unsightly, the damage caused by the disease to the maple tree is minimal.

The powdery mildew fungus overwinters in leaf debris, and to manage the disease be sure to gather up and remove from the property all fallen leaves in autumn. Fungicides purchased from your local garden center can be applied during the growing season as soon as you notice white patches on the maple leaves. Once the fungus has been spoted during the growing season avoid applying nitrogen fertilizers to the tree. Nitrogen increases the production of foliage and provides more material for the fungus. Avoid late evening and overhead watering, this will help reduce the dampness and humidity.

Japanese Maple Leaf Spot: What Causes Spots On Japanese Maple Leaves

A Japanese maple is a great decorative element in the garden. With a compact size, interesting foliage, and beautiful colors, it can really anchor a space and add a lot of visual interest. If you’re seeing spots on Japanese maple leaves, though, you may be worried for your tree. Find out what those spots are and what to do about them.

About Leaf Spot on Japanese Maple

The good news is that when Japanese maple leaves have spots it is most often not a reason to be concerned. Leaf spots are rarely so serious that some method of control needs to be deployed. Generally, your tree will be happy and healthy if you provide it with the right conditions. This is a tough tree that resists most diseases.

One of the most important things that your Japanese maple needs is rich soil that drains well. It will not tolerate heavy soil that holds water and makes its roots soggy. Plant your Japanese maple with compost to enrich the soil, but don’t add much fertilizer later. These trees do not like to be overwatered or overfed. With these conditions, your tree should avoid most diseases and spots.

What Causes Japanese Maple Leaf Spot?

While seeing a few spots on leaves in your Japanese maple is not typically a cause for concern, there may be some reasons for them showing up in the first place, and normally easy enough fixes that you can correct. For example, spraying your tree with water on a sunny day can actually cause spots to burn on the leaves. The small droplets of water magnify the sunlight, causing burns. Keep your tree dry during the day to avoid this.

Leaf spot on Japanese maple trees caused by disease is most likely tar spot—a fungal infection— but even this is not something serious that needs to be treated. On the other hand, it does spoil the look of your tree, beginning as light colored spots and turning black by late summer. To manage and avoid tar spot, pick up debris around the tree regularly and keep it dry and spaced far enough from other plants that air can circulate. Clean up is especially important in the fall.

If you see a serious case of Japanese maple leaf spot, you can apply a fungicide to treat it. This is not necessary in most cases, and the best way to get rid of your spots is to give your tree the right conditions and prevent the disease from coming back next year.

What Can I do About Spots on Japanese Maple Leaves or Trunk?

Gorgeous leaves are the hallmark of Japanese maple trees–until they’re suddenly not!

“My Japanese maple looks really sick and not as full as usual. Leaves fell a lot, and they are all spotted. Is this because we received so much rain in the past several weeks/months? What do I need to do?” asked Linda from North Carolina.

Below, find out some of the reasons why Japanese maple leaves or trunks develop spots.

Why are there spots, powder or a fungus on Japanese maple leaves?

See brown spots on Japanese maple leave?

If you see circular, brown spots on Japanese maple tree leaves, it’s likely a leaf fungus called leaf spot. Or if the spots are more free-form, that could be anthracnose, another common leaf disease.

For some trees, leaf spot and anthracnose can mean a few dots on leaves here and there. In more severe cases, like Linda’s, trees may drop leaves prematurely.

See white spots or patches on Japanese maple leaves?

That’s likely powdery mildew. As the name suggests, powdery mildew causes dusty growth on the top of tree leaves. Like leaf spot and anthracnose, the worst-case scenario is defoliation.

What if those white spots are on the trunk, too?

Lichens look like fuzzy patches on tree trunks. They’re typically found on slow-growing trees like the Japanese maple, so spotting them shouldn’t be a cause for concern.

How can I get rid of these Japanese maple leaf issues? Should I use a fungicide?

Japanese maple leaf problems may look like trouble, but that’s about it! Typically, they don’t affect your tree’s health.
Plus, you’ll be happy to know leaf spot, anthracnose and powdery mildew can be cleared in a few steps.

First:

  1. Avoid getting water directly on tree leaves (by overhead irrigation) because fungi thrive in wet conditions.
  2. If your tree does need a spritz, water in the morning, so they have the whole day to dry.

Then:

  1. Rake up infected leaves in the fall until the tree’s bed is completely clear.
  2. Bag ’em and send them off with your garbage collection. Don’t compost, or you risk spreading the fungus spores all over your yard.
  3. If any branches or limbs look dead, prune those out using proper pruning cuts.
  4. Fungicides aren’t necessary for leaf problems. If you want the extra safety net, your arborist can recommend treatment.
  1. Situate them so as to afford them some shade (especially during the worst of the heat in the afternoon).
  2. Make sure to water them adequately during dry spells. A deep watering done less frequently is better than more frequent, shallow watering. Your goal is to have the soil evenly moist, not soggy (that is, do not overwater). Rather than trying to find a foolproof watering schedule (such a thing does not exist — not across all climates, at least), get into the habit of checking your soil in between waterings to make sure it’s not drying out.
  3. Follow directions carefully when you do use chemical fertilizers. Generally speaking, the proper time to fertilize Japanese maple trees is late winter or early spring (using a slow-release fertilizer). If you do not want to have to worry about being precise in your fertilizing regimen, simply use compost, which will never harm a plant and can be applied at any time.
  4. Spread mulch around the plant (but apply the mulch around your tree in the proper way) to help protect its root system.
  5. Select a sheltered spot when planting a Japanese maple tree, so that it will not be exposed to high winds.

Have the leaves on your gorgeous maple tree become blotted with ugly, dark brown spots? If so, you’re probably thinking that your once beautiful maple tree has become an eyesore. Never fear. The Mr. Tree arborists are here. We’ll tell you exactly what’s causing those troublesome spots and just how to fix them!

Let’s first get to the root of the matter and talk about the cause of those blemishes. Brown spots appearing on maple tree leaves or on the leaves of box elder trees are typically caused by something known as tar spot. This fungal disease gets its name from the fact that the dark brown spots resemble tar. The good news is that while this disease causes blotchy brown spots to pop up on the tree’s leaves, it doesn’t impact the tree’s overall health. The bad news is that in addition to the fact that the spots aren’t exactly aesthetically pleasing, tar spot often causes the tree’s leaves to prematurely fall.

So what should a homeowner look out for when it comes to tar spot? You’ll want to begin checking your maple trees in early spring. If a maple tree has become diseased, you’ll begin to notice light green or yellowish green spots. The spots will gradually become larger and darker until they begin to resemble tar, usually around late September.

Now that we’ve diagnosed the problem, how exactly do we fix it? Since tar spot causes the tree to lose its foliage, you’ll want to be diligent in raking and destroying the fallen leaves by burning, burying, or composting them. This removal process will reduce the chance that the diseased leaves will infect new spring foliage. Without properly disposing of the leaves, however, you run the risk that the fungal spores will be carried on the wind and spread back to the tree’s new foliage.

While destroying all the infected leaves should do the trick, there are certain situations that may call for additional measures. Perhaps, for instance, tar spot has been a persistent problem on your maple tree and you’re looking for a more permanent solution. If this is the case, you may want to contact your local arborist at Mr. Tree to apply fungicide to your maple tree. While it may be possible to tackle this as a do-it-yourself project on smaller trees, larger trees often require a professional fungicide application.

To rid the tree of tar spot, the fungicide must cover every leaf on your maple tree. For mature trees, this can be quite the task. The last thing you want is to take the time and effort to apply fungicide, only to have tar spot return again next year. In order to ensure that the fungicide is applied properly and that every leaf is sprayed, you should contact your local arborist to professionally treat your maple tree.

If you do decide to treat the tree with fungicide yourself, remember that you’ll have to perform multiple sprays in order for the fungicide to be effective. You should perform the first application at bud break and then twice more after a period of seven to fourteen days.

Since tar spot is often a recurring problem, it’s best to try to prevent it altogether. There are several steps you can take in order to decrease the likelihood your maple tree will become infested with tar spot. First, remember that diseases often flourish in wet conditions, so be careful not to overwater your tree. A good rule of thumb is to water the tree so that only six to eight inches of the soil is moist. The soil should be completely dry by the time of the next watering.

You should also prune your tree on a regular basis to increase the amount of sunlight it receives and improve air circulation through the tree’s canopy. Ornamental trees, such as maple trees, should be pruned every year. Finally, add a layer of mulch to your tree on an annual basis as well. The layer should be three to four inches deep and located at least two inches away from the tree.

It’s also a good idea to perform a soil test on your tree from time to time to make sure it’s adequately nourished. A soil test will determine if and what nutrients are lacking. Applying fertilizer can provide nutrients for your soil if there is a deficiency and it is also a good preventative measure for maintaining the overall health of your tree. Soil nutrients should be added to trees every one to three years. While even properly maintained and cared for trees can become diseased, taking these preventative measures will greatly reduce the risk that a tree will become infected.

In addition to properly caring for your trees, it’s also important to have them regularly serviced by a certified professional. Our expert arborists are able to assess your tree’s health and provide honest feedback and recommendations for its upkeep. Not only will regular service appointments increase your tree’s longevity, it will also save you more money over time. Improperly maintained trees will require more attention and may even need to be removed altogether.

While it may be upsetting to see unsightly, brown or black spots on your maple tree’s leaves, you can be assured that this is a problem that can be fixed with just a little time and effort. Your tree’s overall health likely won’t be compromised and with a little TLC, your tree’s leaves will return to normal by the next growing season.

If for some reason the problem persists, just give us a call. We’re more than happy to help you get rid of those pesky spots for good!

Tagged as: caring for Maple trees, Maple leaf spots, Maple leaves spots, Maple tree care, Maple tree disease

Japanese maple leaves

Browned, curled leaves on this Japanese maple are a sign the tree may be infected with Verticillium wilt disease.

(Submitted photo)

Q: Our dwarf Japanese maple tree has grown beautifully for at least 15 years, but then one day last month, boom, the leaves started looking kind of curled. Now they’re all both curled and crunchy. I’m not sure what to do. Do you think the tree is dead? The branches seem brittle. Someone suggested heavily pruning. We love the tree and hate to see it go.

A: That happens sometimes to Japanese maples… and it’s not a promising sign.

Most plant problems give you at least some warning, but Japanese maples (and to some degree other maples) can die pretty quickly from a wilt disease called Verticillium. That would be my first guess based on your description.

The fungus that causes the disease can get in the soil. The tree may fend off the infection, but stress can weaken the tree’s immune system to the point where the disease clogs the wood’s ability to move moisture.

When that happens, whole branches and even the whole tree can shut down pretty quickly. Stresses can include drought, a sudden frost or wet soil.

Something else I saw happen to a lot of Japanese maples last fall was a sudden cold snap that browned out last year’s leaves before they had a chance to turn color and drop. The leaves ended up hanging on trees almost all winter, indicating the trees didn’t have a chance to adequately prepare for winter (another one of those stresses).

Whether your tree has wilt disease or the after-effects of cold weather, I’m not too optimistic about its prospects.

Try scraping off bark from a few branches to see if you see any sign of green underneath. Also try bending a few branches to see if they snap or bend.

Wood that fails those two tests is likely dead, and dead wood won’t come back to life.

If the problem is wilt and some of your tree is still alive, removing diseased wood ASAP can help. One sign of Verticillium is that if you look at the inner wood after a cut, you’ll be able to see darkened sections where the disease has caused clogs.

There are no sprays that I know of (or would use) that are effective at stopping Verticillium once it gets rolling.

If your whole tree is dead and you see evidence of Verticillium in the cut sections, I wouldn’t replace it with another maple. The disease can stay in the soil to reinfect a new tree of the same family.

Penn State Extension has a good paper on this disease that includes replacement species that aren’t susceptible to wilt.

Help for the Home Gardener from the
Contra Costa Master Gardeners’ Help Desk

Japanese Maple leaf scorch…
picture: Missouri Botanical Garden
Client’s Question:
The client has several young Japanese Maples suffering from sun burned and sun scorched leaves. They are concerned about the welfare of the trees and how much to water them. They were told by the nursery to water one gallon every three days.

Master Gardener Response:
Sun Burned/Scorched Leaves: You did not mention what type of sun exposure your maples have so I will address that first. Most Japanese Maples will do well in a location with direct morning sun and shade in the afternoon. Hot afternoon summer sun exposure on many varieties of red Japanese Maples can result in sun burned leaves. I can personally attest to this. With the recent summer winds and hot sun, all of my Japanese Maples have sun burned leaves and some early leaf drop. This often occurs in late August through September but has so far never affected the overall health of my trees.
Leaf scorch can appear on any type of deciduous tree, shrub or plant. During prolonged periods of drought, windy weather or bright sunshine, Japanese Maples are particularly susceptible, especially young trees. In hot weather with dry soil, tree roots cannot absorb enough water to send to the leaves. Foliage may stay on the tree in mild instances, but premature leaf drop occurs in severe cases of leaf scorch.
Watering Japanese Maples: Your question regarding a proper watering schedule is challenging because of several factors including your soil type and whether this is a newly planted or an established tree. Generally speaking, watering of Japanese Maples should be done uniformly throughout the growing season and even more during summer heat. Japanese Maple trees have fairly shallow roots that can dry out easily. Your Japanese Maple requires a consistent amount of water. The amount of water will also depend on your soil type. A clay soil will retain more moisture than a sandy soil. Your nursery’s recommendations on watering may fall short in during a drought season, and especially in light of our summer’s high temperatures and windy days.
The University of Colorado web site referenced below is a great resource on caring for trees in a drought year. However, a Japanese Maple is a moisture loving tree and if it is newly planted, will require additional monitoring and water. A three inch layer of mulch is helpful to provide moist conditions as well as winter protection for the shallow root system. Mulch will also help cool the soil in summer. Some other good cultural practices for your tree’s health include keeping lawn 2-3 feet away from the trunk and keeping mulch about 6 inches from the trunk.
Some Additional References Worth Reviewing on Japanese Maple Care:

General Information on Tree Care in Lawns from the Contra Costa Master Gardeners

Information on Japanese Maples; Master Gardener Newspaper Articles

University of Colorado resource for addressing water needs in a drought situation

Missouri Botanical Gardens on leaf scorch:

Contra Costa Master Gardeners’ Help Desk

Editor’s Note: The CCMG Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we’re open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. (map) We can also be reached via telephone: (925) 646-6586, email: [email protected], and we are on the web at http://ccmg.ucanr.edu/. “Ask a Master Gardener” help tables are also present at many Farmers Markets as well as at the CCMG’s “Our Garden” programs (map). See the CCMG web page for details/locations.

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Leaf scorch

Leaf scorch is a non-infectious, physiological condition caused by unfavorable environmental situations. It is not caused by fungus, bacteria, or virus. The problem may appear on almost any plant if weather conditions are favorable, such as high temperatures, dry winds, and low soil moisture. When large amounts of water evaporate from leaf surfaces, the plant roots are unable to furnish enough water to compensate for the transpirational loss. Leaf tissue dies as a result. Young trees or those that are already in stress due to insect infestations, diseases, or other factors are more susceptible than those growing vigorously and in good condition. Plants that are prone to leaf scorch include Japanese maple, Norway maple, sugar maple, beech, ash, oak, linden, birch, alpine currant, horse chestnut, white pine, rhododendron, viburnum, and flowering dogwood.

SYMPTOMS

Scorch symptoms may differ between plant species, but it typically appears in July and August as a yellowing between leaf veins and along leaf margins, and a browning on the tips of leaves. Since these leaf parts are the last to be supplied with water from the roots, they are usually the first to be affected. Browning of dead tissue often appears without any previous yellowing, extending into the leaf between the veins. Entire leaves may curl and wither when leaf scorch is severe. Scorched leaves are usually abundant on the side of the plant most exposed to prevailing winds and strong sunlight. Leaves on the same branch often show similar symptoms but an entire plant may not be uniformly affected.

On narrowed-leaved evergreens, such as arborvitae, hemlock, fir, pine, spruce, and yew, scorch injury begins from the needle tip progressing inward. When severe, half or all of the needle may turn brown. Scorch injury on evergreens may occur in winter from drying winds when soil is still frozen, as well as during warm, dry summers.

CAUSES

Scorch is a condition and not a cause. Symptoms occur when one or more adverse factors are affecting the plant. In some cases, it is simply a sign that a particular plant is not suited to its exposure or the site it is growing in. Prolonged high temperatures, hot, drying winds, and low rainfall are the most common reasons for leaf scorch. Less obvious causes for scorch include damaged roots, such as from construction or recent transplanting, soil compaction, restricted root space, poor drainage, girdling roots, nutrient deficiency, and high concentrations of de-icing salt, fertilizer, or chemicals. Disease or insect damage to a plant’s root system may cause an imbalance of water between leaves and roots. Wilt diseases, such as verticillium wilt, affects the water conducting vessels in the plant, which sometimes creates conditions for scorch.

CONTROL

Scorch damage alone is insufficient to kill an otherwise healthy plant. Proper treatment depends upon the reason for scorch symptoms; however, good cultural practices that improve general plant health and promote good root growth will reduce the chances of leaf scorch.

  • When dry weather conditions occur over an extended period of time, plants should receive deep supplemental watering every 10 to 14 days. Newly transplanted trees and shrubs should be watered every 7 to 10 days. A slow soaking of the soil is most effective.
  • Conserve soil moisture by mulching plants with a 3-4″ depth of organic mulch, such as woodchips, leaf mold, or bark. Because mulches absorb water from the surface, be sure to water thoroughly so water penetrates into the soil.
  • Apply fetilizers in early spring or late fall, after leaf drop, to minimize the potential of root injury. Always water in well. Avoid applying fertilizer during the summer when soil is drier.
  • Keep lawn fetilizers outside of the dripline of trees and shrubs.
  • Prune any dead, diseased, or crossing branches to reduce the amount of foliage the root system must support.
  • If the cause of leaf scorch is chemical injury, recovery in some cases may be minimal. If de-icing salt or fertilizer burn are suspected, leaching the soil with a slow trickle of water for 24 hours may help in recovery.

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