Japanese maple tree diseases

How to put luster back in those red leaves | The Sacramento Bee

To restore vibrant color to a Japanese maple, first try adding fresh mulch around the tree. Bigstock

Experts tackle readers’ garden questions.

Q: I purchased an 8-foot-tall, roundish-shaped Japanese maple from a local nursery. They said, “In this area, this is the only Japanese maple that will stand up to the hot, direct sun and you won’t believe the fall colors!” The first year, the tree leaves turned a stunning bright red. The next two years, they were just a dull burnt red color. What does the tree need to restore its bright color? More water or some nutrient?

Greg Nakamoto, Lincoln

Master gardener Anna Symkowick-Rose: The Japanese maple (Acer palmatum) is often purchased for its stunning fall color; however, some varieties are not well-suited for the hot, dry climates in the Sacramento area.

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Depending on the variety, your Japanese maple may benefit from being planted in a sheltered spot that is partly shaded and protected. In addition, Japanese maples have high water needs. They like evenly moist soil with good drainage. If the tree is planted in a clay type of soil, this could be contributing to its issues.

Sometimes dull-colored leaves are a symptom of a mineral or nutrient deficiency, the most common being nitrogen and iron. Mineral deficiency can be caused by water-logged soil, root disease and nematodes (a roundworm that can cause plant diseases). To determine if the soil has a mineral deficiency, a professional lab can perform a soil analysis. For a list of soil and plant tissue laboratories, visit

Typically, landscape plants do not require fertilizer; however, they do benefit from a thick layer of mulch (three to five inches) in the form of compost or fine wood chips placed 12 to 18 inches away from the tree trunk. The mulch will help retain moisture in the soil, reduce weeds and slowly release nitrogen. The mulch should be replenished every one or two years.

If there is not mulch already around the tree, try this remedy first. If there is mulch, take some time to replenish it. A fresh layer of mulch may be all that is needed to gain back those beautiful red colors.

For more information on landscape plants, visit the University of California Integrated Pest Management website at www.ipm.ucanr.edu or call the Sacramento County Master Gardener office at the number provided below.

Anna Symkowick-Rose is a UC Cooperative Extension master gardener for Sacramento County.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&[email protected] Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

I have a Japanese maple that has become a green tree rather than a red tree. The tree is planted on the west side of my home and gets a little sun, about an hour or two in the morning and by noon it is in full sun until sundown. The tree does have a little red on the tips of the leaves but looks nothing like our neighbor’s Japanese maple, or like it looked a couple years ago. Also, it looks like a bush and really grew quite a bit this year. Can it be trimmed a little? It has some branches that make it look a bit wild.

The ability of red-leaved varieties of Japanese maples to remain red throughout the growing season is very variable. It is nothing to be concerned about, and you are not doing anything wrong if your tree is otherwise healthy. The variability of coloring may be attributed to the characteristics of the specific variety and its exposure to light conditions. They have the best red color in a spot that is as sunny as the tree can tolerate. This is the point just before the leaves scorch.

Because named varieties don’t come true from seed, they are grafted to a species rootstock to ensure the same coloring and characteristics as the parent plant. Some varieties, like Acer palmatum ‘Atropurpureum,’ are bright red in spring and fall, but only tinged with reddish bronze during the summer months. Some go from fire-engine red to pinkish to green with red veins and petioles; others from purple-red to deep maroon, on to green and back to crimson in the fall. The color varieties are endless! Most likely your Japanese maple is a different variety from your neighbor’s.

Since your tree looks more like a bush, the growth may be coming from the rootstock. Examine your tree to determine where the green branches originate. If there are absolutely no original red leaves appearing on your tree, then it has responded to the dying back of the red-leaved grafted variety by sending up new growth from the base. The rootstock was not a red-leaf variety, as rootstocks are generally selected for their hardiness and vigorous growth, which you have already observed in the bushy green. With the sun and wind exposure of the plant site, and the more typical Michigan winter temperatures, the graft area may have been too stressed. Your choice is to prune what you have or remove it and start over.

Corrective pruning and training can be done at any time of the year, except when the sap is rising in early spring. Cuts should be made just beyond a pair of buds on the twig. Usually, this will then produce two side shoots. When removing a larger limb, like any other pruning, the cut should be made just above the branch collar, the ridge or line where the branch joins an older branch or stem. Major pruning should be done during the dormant season after the leaves have fallen, in October or November, well before the sap starts rising prior to leaf production in the spring. Fine, twiggy growth must be removed, especially from cultivars in the ‘Dissectum’ group. A tree that is too bushy invites insect and disease problems. Pruning is also important to properly display the plant’s structure. Part of the beauty of these maples is the trunk and limb structure and texture, especially during the winter months when the foliage is absent.

Maple Tree Bugs

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They provide shade on a hot day, tasty syrup for your pancakes or a splash of bright color against a dull autumn sky. Of the more than 120 species of maple trees (Acer spp.), 13 are native to North America, growing in U.S. Department of Agriculture plant hardiness zones 3 to 9. Just as there is a wide variety of maple tree species and cultivars, there is an equally diverse assortment of insect pests that threaten these trees.

Leaf Lovers

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Chewed edges or holes on maple leaves are usually signs of a caterpillar pest. Cankerworms, also known as loopers or inchworms, are green to black moth caterpillars that move along leaves in a looping motion. Yellownecked caterpillars are black with yellow stripes and an orange head. They feed in groups and can completely strip small maple trees of their leaves. Other leaf-eating bugs that infest maple trees include tiny, pear-shaped aphids, black and red boxelder bugs and bronze-colored Japanese beetles.

Foiling the Defoliators

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Established, healthy maples rarely die from a season of leaf-eating pests. Natural predators, including birds and parasitic wasps, tend to keep defoliator populations in check. Vulnerable, younger trees may require more aggressive pest treatment to ensure their survival. Picking the pests off saplings by hand is usually enough to protect the tree but pests are not always easily accessible. A naturally occurring bacterium sold at garden centers, Bacillus thuringiensis var. kurstaki, effectively eliminates pest larvae without harming other insects or plants. Mix 1 tablespoon of the concentrated Btk solution in 1 gallon of water in a garden sprayer and spray the tree in the afternoon in late April or early May when caterpillars are actively feeding. Shake the sprayer as you spray and cover all leaf surfaces but avoid breathing in the spray and wear goggles to protect your eyes. A second application may be necessary five to seven days later. Follow the rates on the label as they vary by brand.

Wood Workers

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Some maple bugs remain hidden within the tree but the damage they cause soon becomes evident. The flatheaded appletree borer, Asian longhorned beetle and ambrosia beetle are particular pests of maple wood. The larvae of these beetles tunnel through the hardwood of the tree causing girdled trunks and canopy dieback. While it may be impossible to see inside your tree to identify the pest, exit holes in the trunk or on branches, along with small toothpicklike protrusions of beetle waste jutting out from the bark, are clear signs of a wood boring pest.

Deterring the Tunnellers

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Wood boring insects typically attack already damaged or unhealthy trees. Keep your maple healthy by appropriate watering and fertilizing for the species or cultivar, pruning dead or damaged limbs and protecting the trunk from injury by lawn equipment. Chemical treatments are rarely needed and must be repeated indefinitely. If your maple tree is heavily infested and showing severe damage, it is best to have it removed so nearby trees don’t become infested.

IPM in the South

With their bright red or yellow leaves glowing during this time of year, maple trees are one of the most impressive trees in fall. In most Southern states, they are native, whether they are red, Norway, (Norway is a non-native, invasive tree) Freeman or silver. In the northern states, sugar maples provide us with rich maple syrup for pancakes and waffles. But their beauty and usefulness don’t make them immune from serving as lunch to many insect pests, so if you find that the leaves on some of your maple trees are disappearing rather than winding up on the ground, below is a list of some of the most common insect pests of maples.

Ambrosia Beetles

Adult granulate ambrosia beetle, Xylosandrus crassisculus. Photo: J. R. Baker and S. B. Bambara, NCSU, Bugwood.org.

Two species of ambrosia beetles attack maple trees: Xylosandrus crassiusculus Motschulky (granulate ambrosia beetle) and Xylosandrus germanus Blandford. Both are non-native pests. Ambrosia beetles burrow into the xylum and inject a fungus (the ambrosia), which feeds the larvae. In most cases, the fungus becomes a toxin to the tree, and the tree gradually dies. Infected trees can be spotted by sawdust or “frass” toothpicks that jut out of the trunk. Only licensed professional pesticide applicators have the tools to control ambrosia beetles, but homeowners can monitor maple trees for symptoms of decline or for the “toothpicks” to protect other trees from being affected.

Flatheaded appletree borer

Flatheaded appletree borer, Chrysobothris femorata, larvae in frass-filled gallery. Photo: Amy Fulcher, University of Tennessee, Knoxville.

Flatheaded appletree borer, or Chrysobothris femorata, are bullet-shaped, with a metallic purple abdomen and a metallic bronze ventral (front) side. Adults begin appearing on trees in late spring and early summer. Larvae feed on dividing cambium and sapwood and then bore into the heartwood. Borers prefer trees that are stressed but will attack healthy trees.

Maple shoot borer

Adult maple shoot borers, Proteoteras aesculana are mottled-gray with wings in a wedge shape when resting. Larvae grow in the shoots, causing leaves to wilt. There are usually two generations of adults per season. As the shoots die, the tree attempts to compensate by creating a new growth that can be “forked” from the main direction of the tree. These forks often need to be pruned to retain one main stem, which will need to be staked to grow straight.

Flagging of maple stem caused by maple shoot borer, Proteoteras aesculana. Photo: Amy Fulcher, University of Tennessee, Knoxville

Leaf-feeding caterpillars

Several species of caterpillars appear between summer and fall and feed on maple leaves:

  • Green-striped mapleworm (Dryocampa rubicunda)
  • Yellownecked caterpillar (Datana ministra)
  • Orange-striped oakworm (Anisota senatoria)
  • Bagworms (Thyridopteryx ephemeraeformis)

Late-instar green-striped mapleworms, Dryocampa rubicund, feeding on maple leaves. Photo: S. D. Frank, NCSU

Yellownecked caterpillar, Datana ministra, on the ground in a nursery surrounded by frass pellets diagnostic of caterpillar feeding. Photo: S. D. Frank, NCSU

These caterpillars will quickly defoliate a tree, but unless they are in massive numbers, rarely result in the death of a tree.

Potato leafhopper

Potato leafhoppers, Empoasca fabae, feed on the young leaves and buds of over 200 plant species, including maples. When feeding, leafhoppers cause “hopperburn on leaves, appearing as necrotic lines or severe cupping or stunting. Massively infested trees can have “witch’s broom,” losing the “top” or apical dominance of the tree and having branch tips with too many stems. Red maples are more susceptible to damage by leafhoppers than the other maple species.

“Hopperburn” on maple leaves caused by potato leafhopper feeding. Photo: Amy Fulcher, University of Tennessee, Knoxville


There are two types of scales: armored and soft. In general they are one of the most difficult pests to control in your yard. Armored scales are topped with a waxy cover, called a “test,” that can be separated from the body and do not produce honeydew, while soft scales have no separate test and produce a carbohydrate-rich waste material called honeydew that can grow mold on the tree or on plants beneath.

Dense population of gloomy scales on the bark of a red maple street tree. Photo: S. D. Frank, NCSU

Armored scales feed on the plant tissue, causing branch death and crown thinning. The most common species of armored scales are gloomy scale (Melanaspis tenebricosa) and Japanese maple scale (Lopholeucaspis japonica).

Soft scales feed on the phloem and reduce the amount of energy available for food storage and growth. Twigs and branches begin to die on trees with infestation, and honeydew causes aesthetic damage, also landing on whatever is beneath the infested tree. Long-term infestations can kill the tree. Maple trees are particularly susceptible to scale infestations. The most common and damaging soft scale species are cottony maple leaf scale (Pulvinaria acericola), cottony maple scale (Pulvinaria innumerabilis), calico scale (Eulecanium cerasorum), and terrapin scale (Mesolecanium nigrofasciatum).

Gall-forming insect and mite pests

Although unsightly, galls formed by some insect and mite pests do not damage trees. Galls usually appear in late May and early June and contain a single larva. Larvae exit the gall and drop to the ground to pupate.

The following are the most common mite pests:

  • Gall mites (Aceria elongates): cause blistered white patches on maple leaves and appear in early spring.
  • Maple bladder gall mite (Vasates quadripedes): occurs mostly on red and silver maple trees. Galls are solitary, hollow and have a small exit hole on the leaf underside.
  • Maple spindlegall mite (Vasates aceriscrumena): galls appear in mid-May. Mites leave spindles that are pink or crimson that attach to the leaf surface and are mainly a pest of sugar maples.
  • Maple spider mite (Oligonychus aceris): Eggs hatch in spring and mites feed on the underside of leaves, piercing the leaves and producing a brown stippling. The feeding produces a bronze cast in summer and reduces fall color.

Although most of these pests must be managed by a licensed pest control operator, homeowners can do their part by identifying which pest is attacking their trees. For more detailed information and larger photos, read the original article in the Journal of Integrated Pest Management.

Filed under: featured | Tagged: ambrosia beetle, flatheaded appletree borer, galls, maple pests, maple trees, mites, potato leafhopper, scale tests, scales, soft scale, yellownecked caterpillar |

Red maple tree infestation

Those are tree cattle, Cerastipsocus venosus (Psocoptera: Psocidae). These rather bizarre bugs are large barklice are called tree cattle (or bark cattle) because they occur in large colonies that move about in unison (much like a herd of cattle, I guess). They are harmless and no cause for concern.

Most species of booklice and barklice are very small, almost microscopic in size. Tree cattle are huge in comparison, reaching nearly a ¼ of inch long when mature. Psocids are easy identified by their swollen faces and long antennae. Tree cattle nymphs appear dark gray with pale yellow banding between abdominal segments. Adults have shiny black wings that are held tent-like over their abdomens. The term “lice” as part of the common name of these tree dwellers is quite misleading as these insects are neither parasitic nor louse-like in appearance. As scavengers, tree cattle perform a valuable function in consuming excess accumulations of fungi, algae, dead bark and other materials that occur on tree trunks and large limbs. Tree cattle do not eat leaves or the bark of the tree, nor do they damage the tree by boring into the bark and control measures are not recommended for these insects

Japanese Maple Problems – Pests And Diseases For Japanese Maple Trees

A Japanese maple is a glorious specimen tree. Its red, lacy leaves are a welcome addition to any garden, but they aren’t problem free. There are a few Japanese maple diseases and several insect problems with Japanese maples that you should be aware of to give your tree the care it needs.

Japanese Maple Pests

There are several possible insect problems with Japanese maples. The most common Japanese Maple pests are the Japanese beetles. These leaf feeders can destroy the looks of a tree in a matter of weeks.

Other Japanese maple pests are scale, mealybug and mites. While these Japanese maple pests can attack a tree of any age, they are usually found in young trees. All of these pests present as tiny bumps or cottony dots on twigs and on leaves. They often produce a honeydew which attracts another Japanese maple problem, sooty mold.

Wilting leaves, or leaves that are curled and puckered, may be a sign of another common Japanese maple pest: aphids. Aphids suck plant sap from the tree and a large infestation can cause distortions in tree growth.

Tiny clumps of sawdust indicate borers. These pests drill into the bark and tunnel along the trunk and branches. At worst, they can cause the death of branches or even the tree itself by girdling the limb with their tunnels. Milder cases can cause scarring.

A strong spray of water and regular treatment with either chemical or organic pesticides will go a long way to prevent insect problems with Japanese maples.

Japanese Maple Tree Diseases

The most common Japanese maple diseases are caused by fungal infection. Canker can attack through bark damage. Sap oozes from the canker in the bark. A mild case of canker will resolve itself, but heavy infection will kill the tree.

Verticillium wilt is another common Japanese maple disease. It is a soil dwelling fungus with symptoms that include yellowing leaves that fall prematurely. It sometimes affects only one side of the tree, leaving the other looking healthy and normal. Sap wood may also become discolored.

Moist, sunken bruising on leaves is a sign of anthracnose. The leaves eventually rot and fall. Again, mature Japanese maple trees will probably recover but young trees may not.

Proper annual pruning, cleaning up of fallen leaves and twigs, and yearly replacement of mulch will help prevent the infection and spread of these Japanese maple tree diseases.


By far the most common causes of damage to Japanese maple trees are incorrect watering, frost and sun. Especially when Japanese Maples are grown in containers they require even watering.

Planting them in the correct position should avoid much of the damage caused by high winds, extremes of cold and high heat.

Article and pictures by David Marks.



Aphids are tiny insects about 3mm long with the most common types being black fly and green fly. Other types do exist but are rarer. The first appear on juicy, tender young shoots. As the colony increase in number they spread to the underside of young leaves.

They cause damage in two ways. Firstly, they cause leaves to curl up and eventually fall off. Aphids also excrete a gooey liquid often referred to as ‘honey dew’. This attracts lots of diseases which becomes clearer when the ‘honey dew’ changes colour often going black.


Overfeeding, especially in spring, encourages aphids. The plant will quickly produce lots of soft new shoots which are readily colonised by aphids. So, avoid overfeeding your plants especially in the spring.

Early action when greenfly are first noticed or anticipated will enable more successful organic treatment of aphids. Roses are particularly affected by by aphids so the minute you see aphids on roses in your garden or area inspect other shrubs and trees for signs of an aphid attack.

If you aren’t particularly squeamish many of the aphids can be killed by running your forefinger and thumb over leaf and shoot surfaces. This will simply squash them to death! Water over the leaves after doing this will wash many of the dead aphids away. A spray is even more effective.

Preventative treatment that works is a spraying with 2 litres of water containing a teaspoon of washing up liquid. It is thought that the diluted washing up liquid clogs up the aphids and causes them to die. It has no ill effects on the plants themselves. Concentrate spraying on new shoots and the undersides of leaves.

Encouraging other beneficial insects which eat aphids is also another approach which works well. The main ‘consumers’ of aphids include ladybirds, hoverflies and lace wings. Encourage them into your garden by planting marigolds and calendula. Strangely, a patch of nettles is also an excellent way of attracting aphid eating insects. They attracted to the aphid species which colonise nettles but which affects no other garden plants.


Use only as a last resort but often it is the only solution when an aphid attack has become out of hand. There are lots of systemic insect sprays on the market which work well. Check the label to ensure they are good for controlling aphids. Systemic sprays used for roses are excellent.


Verticillium Wilt affects lots of plants, shrubs and trees. Most commonly affected are Japanese Maples, chrysanthemum, carnations, cotinus and catalpa. Strangely, strawberries are also affected.

The main sign of infection is leaves turning brown, especially near the base. Plants begin to wilt in warmer weather although they may temporarily recover if the weather turns colder.

Woody plants such as acers and chrysanthemums will have brown marks on the wood immediately below their bark. Branches may die completely in parts of the plant.


This is a disease which is first spread in the soil. It enters the plant through damaged or weakened roots. Once the Verticillium Wilt fungus infects the roots of the plant it spreads upwards. The plant’s natural defence system attempts to isolate the fungus but in the process it prevents water being passed around the plant internally. This causes parts of the plant to die.


There is no treatment for Verticillium Wilt. Managing an infection is a matter of damage control because the disease can be passed to other plants. One common source of infection is the soles of your boots transferring infected soil from one part of the garden to another.

The plant or tree should be dug up with as many of the roots as possible and burnt completely. Be careful when transferring the plant and roots to the point of burning, do not allow any possibly infected soil to come into contact with any other soil or plant.

Unfortunately, the disease can remain in the soil for up to 15 years so do not plant any susceptible plants on the area for many, many years. Sometimes a new plant will appear to grow successfully for two or three years before it also shows signs of the disease. Don’t waste your time cleansing the soil with Jeyes Fluid or similar preparations, they do not get rid of Verticillium Wilt in soil.

Ideally the area should be grassed over and left. However there some plants which have immunity to Verticillium Wilt and these should grow successfully on an infected site. Apple and pear trees both do well but not plum trees. Conifers are resistant and these come in a variety of forms and sizes. Other plants and trees to consider with excellent immunity include, beech, ginkgo, hawthorn, hornbeam, mountain ash, sycamore and walnuts.


Vine Weevil

Vine weevils have two distinct appearances depending on the stage in their life cycle, When they are grubs / larvae in the soil a vine weevil is about 2cm / 5/8in long when fully grown, white at first but turning brown. Their bodies are “C” shaped and they can be found under the soil near the main stem of the plant.

When they emerge from the larvae the adults are 1cm / ¼in long. They look like small beetles, browny black coloured and pear shaped, the heads are a dark black. The top part is pitted with lots of little indentations. They have what appear to be wings but in fact they are unable to fly.


As adult “beetles”, vine weevils will eat the edges of leaves. This attack disfigures the leaves but healthy plants, trees and shrubs will recover from this damage. However the grubs eat the roots and even sometimes the main stem of plants which, if left untreated, is often fatal.

Note that plants, trees and shrubs grown in open ground are not affected, attacks occur on plants grown in containers. Understanding the life cycle of the vine weevil is essential to minimising the damage they do to plants.


July to August
The adult lays eggs near the surface of the soil. If the soil is mulched the eggs will most likely be laid in the mulch. Each adult will lay about 200 eggs which take about 3 weeks to hatch. Immediately the eggs hatch the emerging larvae begin feeding on the smallest roots of the affected plant. as the larvae grow in size they will ‘upgrade’ to feeding on larger roots and in some cases the main root.

September to November
As the temperature of the soil begins to cool the larvae will gradually stop eating and burrow down lower into the soil where they hibernate over the winter.

March to June
The larvae start feeding on larger roots as the soil temperature increases, In May to June they transform (‘pupate’) into adults.


Vine Weevils prefer container grown plants and small trees. Almost any shrub or small tree can be affected although vine weevils do have a preference for camellias and rhododendrons. Japanese Maples are also a plant of choice.

First attack the adult vine weevils and this can only be done manually. When an adult vine weevil is attacked by a predator it’s natural reaction is to fall to the ground and play dead. Their browny /black colour makes them very difficult to spot on soil. The plan of action should be to lightly shake the shrub which will cause the bugs to fall off – an upturned umbrella will catch many of them. Another method is to lay white paper around the plant so all the Vine weevils to be seen more clearly.

The next treatment is to encourage wildlife which enjoy eating the vine weevil at all stages of their lives. This includes birds, hedgehogs, frogs and toads. One particularly good method is to encourage birds into your garden by providing them with food and water. Position the bird feeder as near to the affected plant(s) as possible.

Biological control of the larvae stage stage of the vine weevil is a good method of interrupting their life cycle. There are a few nematodes readily available from garden centres or online which will attack vine weevils. Our favourite is Steinernema kraussei mainly because it remains active at lower temperatures compared to other nematodes. This allows it to be applied from mid-March through to September.

There are chemicals which can be applied to the soil but they should not be used for edible plants although they are fine for Japanese Maples. Search on the internet for “vine weevil chemical control” if you wish to use the chemical route but the previous suggestions will work as well if not better.

Caring for Your Maple Tree

Maple Tree Types

Maples are deciduous trees characterized by opposite leaf arrangement and spectacular fall color. The flowers are upright and green, yellow, or red in color depending on species, and the fruit appears in winged clusters which hold the seeds of this self-pollinating tree.

There are approximately 125 maple tree varieties, and each one has different characteristics and site requirements. The size of the tree varies by species, but they can grow anywhere from 18 to 80 feet.

Some of the most common varieties include:

Red maple trees have red blossoms in the spring, red fruit in summer, scarlet leaves in the fall and crimson bark and twigs in winter. Red maple trees thrive in wet soil, and are also sometimes called swamp maples.

Sugar maples turn brilliant shades of yellow, orange, and bright red in the fall. They have a gray bark and a sensitive root system. Their sap is also the source of maple syrup.

Japanese maples are lovely ornamentals, meaning that they remain smaller in size. They’re known for their interesting branching structure, bright color, and year-round interest.

Maple Tree Care

Maples tend to have shallow root systems, which can lift walkways and driveways as they mature, so be sure to plant them appropriately. Prune, water, and fertilize maple trees regularly to maintain optimal health.

Newly planted maple trees will benefit from a root enhancer like ArborKelp®, SavATree’s exclusive seaweed biostimulant fertilizer. This aids in tree establishment, promotes root growth, and heightens stress tolerance.

If you’d like to establish maple tree varieties in your landscape, we can connect you with a vetted landscape expert who can help you purchase and plant new maple trees.

Mature and established trees benefit from fertilizer feedings of organic-based macro and micronutrients for the nutrition necessary to sustain their health.

Preventing Maple Tree Diseases & Pests

There are several damaging maple tree diseases and pests. Some of the most common are:

Verticillium Wilt – Also called maple wilt, this fungus is a common and serious problem that can kill trees. This infection starts in the root system and works its way up the maple tree, resulting in cankers and dieback. Signs of maple wilt include scorched-looking leaves and diseased branches with unhealthy leaves. Occasionally olive-colored streaks can be found in the sapwood.

Anthracnose – This disease results in extensive defoliation, shoot dieback, and twig death. Often confused with frost damage, signs of anthracnose include brown areas on leaves, canker on the trunk and main branches, and purplish-brown areas along the veins of the leaves.

Tar Spot – This disease affects several maple species and causes large, tar-like spots on the leaves. This is a fungal disease, and a good preventative measure is to rake up any dead or fallen leaves around the tree.

Asian Longhorned Beetle – This insect damages the sapwood beneath the bark layer, preventing the tree from properly transporting nutrients and water. Once a tree has an Asian longhorned beetle infestation, it will generally die within 1 to 2 years. Learn more about the Asian longhorned beetle.

Of course, these trees are susceptible to other problems as well. Other maple tree diseases and pests include:

  • Root rot
  • Gall mites
  • Cankerworms
  • Aphids
  • Cottony scale
  • Petiole borers
  • Leafhoppers
  • Boxelder bugs

Many of these insect and disease conditions can weaken the tree and lead to tree death if not treated. If you suspect a problem with your trees, call an arborist right away for an evaluation and treatment options.

Pruning Maple Tree Leaves

Pruning is the best way to maintain size while preserving (or even improving) your maple’s structure, vigor, and life-span. Pruning offers a host of benefits:

Reduces storm damage – Pruning can reduce specific defects or structural problems in a maple tree to greatly lessen the risk of failure.

Prevents disease – Broken, diseased, or dead branches are typically removed in order to prevent decay-producing fungi from infecting other areas of the tree.

Increases airflow – Removal of live branches is occasionally necessary to allow increased exposure to sunlight and circulation of air within the canopy. This assists in reduction of certain diseases.

Promotes healing – We also advocate the removal of branch stubs to promote successful and proper healing of wounds.

Want an expert opinion on your maple? Contact us for more information on pruning or any of our other maple tree care services.

Maple Insects & Diseases


Asian longhorned beetle
A new and potentially serious threat to some of North America’s most beautiful and popular trees is the Asian Longhorned Beetle (Anoplophora glabripennis). Native to parts of Asia, the beetle is believed to have arrived in North America in the wooden packing material used in cargo shipments from China. Isolated Asian Longhorned Beetle infestations have been discovered in Brooklyn and Amityville, New York, and in Chicago, Illinois


Anthracnose (Discula spp., Kabatiella apocrypta) is a name for a group of diseases caused by several closely related fungi that attack many of our finest shade trees. It occurs most commonly and severely on sycamore, white oak, elm, dogwood, and maple. Other host plants that are usually only slightly affected include linden (basswood), tulip tree, hickory, birch, and walnut.

Verticillium Wilt
Maple wilt, also called Verticillium wilt, is a common and serious disease of maples. The destructive soil-borne fungus, Verticillium, kills many maples each year throughout North America. Norway maples seem especially sensitive to infection by Verticillium. Silver, red, sugar, sycamore and Japanese maples are also susceptible.

Sapstreak disease of sugar maple
Sapstreak disease, caused by the fungus Ceratocystis coerulescens, is a serious threat to sugar maple forests. Although the disease is causing only minor damage at present, it has the potential to become an important problem. Sapstreak is a fatal disease; infected trees do not recover. In addition, timber salvage value is low because the wood is discolored.

Tar Spot
These dramatic but inconsequential diseases of numerous maple species cause small to almost one-inch diameter tar-like spots on leaves. The fungus overwinters on fallen leaves, then infects the upper surfaces of leaves in spring during moist conditions. Usually the best approach is to do nothing. Cleaning fallen leaves in the autumn can help reduce the amount of fungus that overwinters.

What does Maple Syrup Have in Common with an Invasive Insect?

Posted by Rhonda Santos, APHIS Asian Longhorned Beetle Eradication Program in Animals Plants Feb 21, 2017 Two Asian longhorned beetles on maple tree

Today is National Maple Syrup Day! So, what does maple syrup have in common with an invasive insect? Well, if the insect is the Asian longhorned beetle, then they both can come from maple trees. Obviously, we want the maple syrup and not the invasive beetle. But who cares? And why should anyone care? Well, I care and here’s why:

Not only do I work for the USDA’s Animal and Plant Health Inspection Service, an agency that is actively fighting known infestations of Asian longhorned beetle in three different states, but I also am a native of Vermont.

According to a 2013 release about Maple Syrup Production issued by USDA’s National Agricultural Statistics Service, Vermont is responsible for 40% of the United States’ maple production – that’s 1,320,000 gallons from just one tiny state! It typically takes 50 gallons of sap to make one gallon of maple syrup. A single maple tree can produce an average of 15 gallons of sap per season, so you need at least 3-4 maple trees just to make the one gallon of syrup. Many Vermonters like to say they have maple syrup running through their veins; it’s simply that important, valued, needed and wanted.

But the Asian longhorned beetle is a real threat to our country’s maples trees and to 12 other types of hardwood trees too. It doesn’t belong here and we don’t want it here. When the beetle attacks trees, its larva feed on the heartwood or center part causing tunneling that can make a cross-section of a tree look like a piece of Swiss cheese. The damage weakens the tree and eventually the tree will die.

The best line of defense is you. In honor of National Maple Syrup Day, and for the love of all things maple, I am asking you to take a look at your trees. If you are outside, just walk up to a tree and see if it has round holes on the trunk and/or branches – these holes are caused by the adult beetle when it exits the tree. The holes are a little bit smaller than a dime and just a bit bigger than the circumference of a pencil. You won’t see the adult as they die off with the first hard frost, but you can still see the holes and other signs of damage.

The sooner we know about an ALB infestation, the sooner we can do something about it, so please report any sightings. Long live National Maple Syrup Day!

Category/Topic: Animals Plants

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Royal Rife Apr 28, 2014

National Maple Syrup Day. Are you kidding? Is someone paid good money to come up with these “days”?

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