How to Identify and Manage Common Japanese Maple Diseases

A flexible specimen tree for the panorama, the Japanese maple is actually a factor of magnificence – which, while you see one which’s diseased, makes it that rather more of a tragedy.

And similar to a Shakespearean unhappy story, a sick Japanese maple can simply finish in dying. Not that of an individual, fortunately, however of your tree.

A useless Acer palmatum can nonetheless hit you within the feels fairly exhausting, although, particularly should you’ve been nurturing it for an excellent lengthy whereas.

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Armed with the data of what to search for, it can save you your Japanese maples, and even preserve them from contracting a illness within the first place.

That’s why we’ve whipped up this information on the most typical diseases of A. palmatum. The way to establish them, how you can handle them, how you can stop them… it’s all coated right here.

Right here’s the checklist of illnesses:

In the event you’re in want of a refresher about how you can develop Japanese maples, make sure to take a look at our information.

1. Anthracnose

Enjoyable reality in regards to the phrase “anthracnose”: it’s a catch-all time period for a bunch of associated fungal illnesses that normally trigger darkened foliar lesions.

And anthracnose can infect many vegetation, together with Acer species equivalent to Japanese maples.

A number of fungal pathogens may cause anthracnose in Japanese maples – Aureobasidium apocryptum, Discula campestris, and Colletotrichum gleosporoides are just a few vital ones.

Overwintering in useless leaves, twigs, and buds, the pathogens produce fruiting our bodies in spring, which launch spores that unfold through wind and rainwater to uninfected buildings.

As soon as contaminated, Japanese maple foliage reveals tan or black blotches alongside leaf margins and first veins. Contaminated foliage will then flip necrotic, curl, and drop.

In time, this will defoliate bushes prematurely, in addition to result in the decline of careworn, weak, younger, and/or lately transplanted Japanese maples. 

Since spores unfold through splashing water and wind, keep away from overhead irrigation and sufficiently house bushes while you plant.

Contaminated leaves and branches must be promptly pruned and destroyed, whereas dropped leaves, branches, and different bits of detritus must be eliminated to stop pathogen overwintering and additional unfold.

For at-risk Japanese maple bushes, preventative fungicide sprays in early spring might help. Begin at bud break, and repeat twice at two-week intervals. Make sure you comply with the label’s directions!

2. Canker

In the event you’re a bit squeamish, be happy to skip this one.

Cankers end result from open wounds turning into contaminated by fungal or bacterial pathogens. Able to showing on any a part of a Japanese maple tree’s bark, cankers are typically brown to reddish, sunken, and irregularly-shaped.

Additionally they ooze moist sap, in addition to stink one thing terrible.

The foliage past a canker can change into stunted, chlorotic, browned, and curled.

In time, the pathogen can unfold right into a tree’s vascular system, which might trigger additional wilt and department dieback.

Plus, a canker can produce its personal spores, which unfold in moist and windy circumstances to type extra cankers elsewhere.

Canker prevention is easy: keep away from unnecessarily wounding your Japanese maple and preserve it wholesome. Additionally, make sure to frequently sterilize your gardening instruments rubbing alcohol.

For a Japanese maple presently carrying cankers, prune away contaminated branches a number of inches behind the symptomatic tissue.

Make sure you eliminate them promptly, and solely make your cuts in dry climate with sharp, sterile blades. To handle cankers on the trunk, you must seek the advice of an arborist or plant pathologist.

3. Leaf Scorch

Leaf scorch is technically an abiotic situation, that means it’s a physiological situation brought on by the surroundings, quite than a organic pathogen.

Brought on by excessive temperatures, dry winds, low soil moisture, or some mixture of those, leaf scorch manifests in brown or grey foliar margins, in addition to chlorotic or darkened areas between leaf veins. In time, scorched foliage can flip brown, dry, and brittle.

In gentle instances, the foliage can survive with solely a little bit of disfigurement. Extra extreme instances will trigger untimely defoliation, in addition to twig drop.

Both manner, signs are typically stronger on the facet of the Japanese maple tree that’s most uncovered to wind and daylight.

Fortunately, leaf scorch is normally a short lived situation brought on by a scorching, dry summer time. But when leaf scorch occurs yr after yr, then your tree could lose vigor and change into a bit stunted.

Stopping and halting leaf scorch are each fairly easy: present correct irrigation and moisture-retaining mulch.

So long as you’re employed to counteract the moisture loss with sufficient water, the leaf-scorched Japanese maple ought to produce stunning leaves subsequent spring like nothing even occurred.

4. Phyllosticta Leaf Spot

Phyllosticta leaf spot is fairly straightforward to note. Or “spot,” should you’ll pardon the pun.

It’s brought on by the fungus Phyllosticta minima, which overwinters in fallen foliar detritus. In spring, it produces spores that unfold through wind and splashing water to the budding foliage of close by A. palmatum specimens. 

New spores produced on contaminated foliage can then unfold all through the cover, and even transfer to close by bushes. In severe instances, the Japanese maple could be defoliated for a time, however the leaves will sometimes develop again.

Contaminated leaves exhibit yellowish to tan spots, with darkish reddish to purplish borders.

The facilities can typically be clear and even drop out, leaving contaminated foliage with extra shot holes than a John Wick background actor.

Take a better take a look at the leaves and also you’ll discover black fruiting our bodies within the useless sections.

It’s vital to rake up close by foliar detritus in fall to take away websites for overwintering pathogens.

Overhead irrigation must be averted, together with putting specimens too carefully collectively. In the event you discover severely contaminated leaves, pruning them might help restrict unfold.

Preventative functions of fungicides could be useful for younger, beforehand diseased, or in any other case at-risk Japanese maples.

Three functions ought to suffice: one at bud break, one about 10 days later, and one when the foliage is totally shaped.

5. Phytophthora Root Rot

Some actually horrible issues begin with “ph,” equivalent to phonies, phishing, and phlegm. Phytophthora root rot, brought on by water molds within the Phytophthora genus, is one other.

As with most root rots, Phytophthora begins with an excessive amount of moisture, whether or not your Japanese maple receives an excessive amount of water, the soil it’s sitting in doesn’t drain nicely, or each.

When the soil is excessively soggy, it serves as the right surroundings for the soil-borne resting spores of Phytophthora species to germinate and produce motile spores.

These motile spores unfold through free water to penetrate roots, trunks, and branches of close by vegetation.

As soon as contaminated, a Japanese maple will begin to look drought-stressed, satirically sufficient. Leaves flip discolored, bark darkens, roots flip necrotic, and the plant as a complete will decline and finally die.

Prevention is so simple as not overwatering, offering well-draining soil, and avoiding planting in contaminated soils.

Make sure you choose vegetation that you realize are disease-free, and be happy to make use of foliar sprays of fungicides, which’ll be absorbed and journey down into the roots.

For a specimen that’s already contaminated, stop supplemental irrigation instantly. If the plant can’t get better by itself, then you definitely’ll need to take away and destroy it.

6. Powdery Mildew

Brought on by a number of genera of carefully associated fungi, powdery mildew isn’t the grossest of circumstances on this checklist.

If something, it reveals up on leaves trying like a delicate coating of previous child powder, a nice software of moldy parmesan cheese, or maybe a extreme case of dandruff.

Okay, I suppose that’s really fairly nasty.

No matter you assume the grayish-white powder seems like, it spots and coats foliage, leaving it with irregular development, distortion, and discoloration. Because it progresses, foliar chlorosis, browning, desiccation, and even untimely drop can happen, in addition to a decline in general plant well being.

Because the fungi survive the winter by residing in fallen plant particles earlier than producing spores in spring, it helps to rake up close by leaves and twig detritus in fall.

And because the spores want cool and humid circumstances to unfold, keep away from overhead irrigation and crowding vegetation collectively.

Take away contaminated foliage and stems as you discover them. You’ll additionally need to take away any suckers that pop up close to the bottom of the Japanese maple tree – these are particularly weak to an infection.

Promptly making use of fungicides as soon as signs are famous can even assist to stop additional unfold.

You may study extra about powdery mildew in our information.

7. Pseudomonas Tip Blight

A illness of many decorative vegetation, Pseudomonas tip blight could be dangerous information for a Japanese maple.

This situation is brought on by the bacterium Pseudomonas syringae, which overwinters in fallen plant detritus or within the wholesome tissue of the plant itself.

In cool and moist spring climate, it spreads through wind, splashed rain, bugs, and/or pruning instruments to enter plant tissue via wounds or pure openings.

As soon as inside, the micro organism produces toxins that transfer via the xylem to trigger issues.

Mentioned issues embody shoot discoloration, shriveling, and dying.

Consider a gangrenous limb in want of amputation, and that’s what contaminated branches and foliage are like, for essentially the most half. And if sufficient branches fall sufferer, then all the Japanese maple tree can perish.

Make sure you prune away any contaminated tissues with sterile instruments while you discover them, however solely throughout dry climate – the pathogen might unfold in moist circumstances.

If any contaminated leaves and twigs drop, rake these up as nicely. And make sure to keep away from high-nitrogen fertilization, which might result in weak late-season development.

If the tree is severely contaminated – i.e. greater than half of the crown is symptomatic – then eradicating and destroying the specimen could also be your finest guess.

8. Tar Spot

 Simply by the identify, you’ll be able to most likely think about how gnarly tar spot seems.

In maples, tar spot is brought on by varied fungal species from the Rhytisma genus, which overwinter in fallen foliage.

Come spring, the spots cut up, releasing spores that hitch a trip on wind to close by foliage. If a leaf turns into contaminated, tar spots type and the cycle continues.

Mentioned spots have a tendency to indicate up in late spring to early summer time as small, pale yellow areas lower than an eighth of an inch in diameter.

Over time, the spots develop and change into darkish brown or black, with yellow borders. This recognizing interferes with photosynthesis, barely impeding the tree’s development and growth.

Fortunately, tar spot doesn’t actually harm the host over the long run, since new leaves will type yearly.

Apart from raking up and destroying fallen leaves, in addition to pruning contaminated ones as you discover them, you can strive utilizing foliar fungicides, aiming for as a lot protection as potential.

Be taught extra about tar spot and different Japanese maple leaf spots in our information.

9. Verticillium Wilt

A illness of many alternative bushes and shrubs, verticillium wilt afflicts Acer species with a specific ease and severity, to the purpose that it’s usually nicknamed “maple wilt” amongst arborists.

Verticillium wilt is brought on by two fungal species of Verticillium: V. albo-atrum and V. dahliae.

Mendacity dormant in soil and plant roots, these pathogens transfer to wounds or pure openings in roots and branches, touring through flowing water, infested soil, wind, or contaminated pruning instruments.

As soon as contained in the plant’s vascular system, the pathogen halts the movement of water and vitamins, resulting in foliar wilt, browning, and untimely drop.

These signs are sometimes restricted to particular sections of the tree at first, earlier than spreading all through the crown.

Contaminated department bark reveals discolored streaks, and all the Japanese maple can steadily decline earlier than perishing.

It’s vital to prune away contaminated branches ASAP, way back to the discolored bark tissue goes. Use sterilized pruning instruments, and ensure to destroy any pruned materials.

If the illness outpaces your pruning efforts and/or afflicts the vast majority of the tree, you might have to take away and destroy all the plant.