With lush foliage, showy blooms, and aesthetically pleasing types, magnolia timber (Magnolia spp.) are beloved members of any decorative panorama.
Sadly, their magnificence might be marred when disease-causing pathogens infect magnolia timber.
Generally magnolia ailments might be fairly innocuous, whereas different instances they’re fearsome, hard-to-beat afflictions.
However regardless of the illness you’re preventing, there’s virtually all the time one thing you are able to do.
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On this information, we’ll focus on 13 widespread magnolia ailments, and establish and deal with them, so you’ll be able to convey your tree again to full well being.
Right here’s what I’ll cowl:
13 Magnolia Tree Illnesses
A fast reminder for conserving any plant disease-free: correct and sanitary cultivation is vital.
A wholesome plant is healthier at preventing ailments than one which’s already struggling to remain alive. By offering your magnolia with all the pieces it must thrive, you’ll additionally enhance the percentages that it’ll survive threats to its well being.
In the event you want a refresher on cultivating magnolias, check out our growing guide.
And I do know “sanitary” is a bit oxymoronic, since backyard work is of course a grimy endeavor.
However by conserving your gardening implements sterile and being aware of how pathogens can unfold, you’ll be doing all of your magnolia timber, and different vegetation in your backyard, an enormous favor.
1. Algal Leaf Spot
In the event you didn’t suppose that algae might afflict land-dwelling timber… suppose once more.
Attributable to the parasitic alga Cephaleuros virescens, algal leaf spot spreads by spores that journey by way of wind and rain to close by plant surfaces. Multiplying in quantity, the spores accumulate in raised blotches or patches on leaf and stem surfaces.
Grayish-green, brown, or orangish in coloration, these spots trigger localized chlorosis, necrosis, and leaf drop, together with total plant weak spot.
The causal algae overwinters in contaminated foliage and twigs, whether or not they’re on the plant or on the bottom. The next yr, the cycle begins anew.
Remove potential overwintering websites by raking up close by plant detritus, and take away noticed leaves and twigs everytime you first discover signs.
Correctly house and prune your magnolia timber to permit for sufficient airflow inside their canopies, which alleviates these moist, humid circumstances that many pathogens love.
If the vast majority of the leaves in your tree are symptomatic, you’ll be able to apply a copper fungicide.
Simply know that fungicide sprays usually work higher as a protectant, fairly than a remedy. So make a remark in your diary to spray your magnolia preventatively the next spring.
Southern Ag’s liquid copper fungicide is good, and yow will discover it available via Amazon.
If an contaminated tree offers you vital hassle yr after yr regardless of your greatest efforts, eradicating the plant and destroying it might be a sensible selection.
2. Anthracnose
Attributable to species within the Colletotrichum genus of fungi, anthracnose and its signs are about as refined as an open-carried .50-cal revolver at a Texas fuel station. Not very.
Overwintering in useless leaves and branches, the spores of the causal pathogen unfold by way of splashing water to close by foliage, inflicting massive, angular spots close to leaf margins.
Because the illness progresses, these spots develop a burned look, surrounded by a yellow halo of discoloration.
On higher surfaces of the magnolia foliage, the spots develop blister-like fruiting our bodies, which ooze plenty of pink spores. Ultimately, total leaves can flip chlorotic yellow and drop.
Foliage needs to be eliminated as quickly as symptomatic spots are observed. Close by leaf and twig detritus needs to be collected and disposed of, as nicely.
If the vast majority of leaves in your magnolia begin to develop into symptomatic, a fungicide program could also be wanted – search for merchandise containing mancozeb as a principal energetic ingredient.
You’ll find Bonide’s mancozeb flowable with zinc in 16-ounce focus available at Amazon.
Make sure you observe the producer’s instructions for utility.
3. Bacterial Blight
Blight, noun: a factor that spoils or damages one thing. Within the case of bacterial blight, that sounds about proper.
The notable signs of bacterial blight – brought on by Pseudomonas syringae pv. syringae and Pseudomonas cichorii – are small, darkish, necrotic spots, every surrounded by a yellow halo, which slowly increase into blights of bigger, extra irregular lesions that intervene with plant photosynthesis.
Spreading by way of wind, bugs, or contaminated instruments, the causal micro organism enters vegetation via flower buds and/or wounds, resulting in the event of sunken, contaminated cankers.
Magnolia branches with cankers can exhibit foliar and stem wilt. Oozing darkish and sticky fluid, these cankers additionally act as overwintering websites for the pathogen.
Though usually seen extra usually in plant nurseries than the panorama, bacterial blight can nonetheless be a harmful menace to your timber.
Prune contaminated shoots once you discover them, ensuring to sterilize your instruments between cuts.
If pruning your magnolia doesn’t present passable management, copper-based bactericides can be utilized to handle the illness in vulnerable environments.
4. Bacterial Leaf Scorch
A systemic, power, and incurable illness. Gotta love these.
Bacterial leaf scorch kicks off with Xylella fastidiosa micro organism invading a magnolia tree’s xylem, which is mainly a plant’s inner water plumbing.
Overwintering within the xylem yr after yr, the micro organism can entry any and all branches related to the trunk. Leaves flip brown in midsummer, beginning with the older ones and ending with these closest to the department ideas.
Separated from the wholesome tissue by a skinny yellow border, the brown sections step by step work in direction of the middle of every leaf, ultimately inflicting them to show fully brown and drop from the tree.
As years move, this browning-and-dropping happens earlier and earlier within the season, weakening and killing components of the tree in bits and items till your complete plant ultimately perishes.
As bacterial leaf scorch is unfold by way of xylem-feeding bugs akin to leafhoppers and spittlebugs, it pays to handle your native pests.
When branches begin to flip brown and die off, take away them. If total timber are in extreme decline, take away these as nicely – chances are you’ll have to recruit an expert’s assist for this.
You may strive springtime injections of oxytetracycline antibiotics into the foundation flare, however these will probably solely cut back bacterium ranges sufficient to delay signs by a few weeks.
You may seek the advice of an arborist in case you’re curious, however in any other case, I’d take solace in what J. R. R. Tolkien referred to as “the lengthy defeat,” and take away contaminated specimens.
5. Bacterial Leaf Spot
Save for the causal pathogens being species of micro organism within the Xanthomonas genus fairly than Pseudomonas, bacterial leaf spot causes related signs to these of bacterial blight: darkish foliar spots surrounded by faint yellow discoloration, which results in hindered photosynthesis and diminished aesthetics.
And the “hows” of managing each in magnolias are fairly related. Prune affected plant tissue and spray with copper-based bactericides within the case of in depth an infection.
6. Cankers
We’ve talked about these already, however they’re positively dangerous and annoying sufficient to warrant their very own entry.
Cankers are necrotic, localized lesions that manifest on the branches, trunks, and/or roots of timber. Usually sunken and rounded in look, cankers additionally are likely to exhibit discoloration and ooze with gnarly, sticky fluid.
Attributable to quite a lot of completely different bacterial or fungal pathogens after mechanical or environmental harm, cankers could cause native or systemic dysfunction in foliage and bark. Foliage will flip yellow, brown, and wilted, bark will peel, and plant tissues will die.
As cankers can happen by way of wounds, it pays to maintain your magnolias protected from blades, trimmers, and tree-climbing youngsters.
Prune with warning, give root flares a large berth when working within the neighborhood, and restrict Little Timmy’s climbing to the playground till he learns to not peel away bark along with his foot placements.
Once you discover a canker on a magnolia department, prune your complete department. Make your cuts a number of inches beneath the canker in direction of the trunk, to remain on the protected facet.
If cankers are on the trunk or roots, I’d suggest you seek the advice of with an arborist or plant pathologist – eradicating these takes ability that’s onerous to study as an beginner.
7. Crown Gall
I’ll say, crown galls aren’t as gross as cankers. They’re, nonetheless, fairly honkin’ in measurement and conspicuous-ness.
Attributable to the fun-to-pronounce Agrobacterium tumefaciens, crown galls are basically tree tumors.
When A. tumefaciens micro organism in close by soil infects a plant via wounds, it stimulates the plant to provide a big, swollen mass of tissue on trunks, stems, and even roots that gives ample sources for the pathogen to feed on and reproduce in.
This may be dangerous to younger magnolia vegetation specifically, as gall growth can stunt their progress, inhibit water and nutrient transport, and go away them top-heavy and susceptible to breakage.
However in older magnolias, the drawbacks of galls are beauty and minor.
You may lower out galls in the course of the dry season if what you’re doing, or you’ll be able to recruit somebody with extra know-how to do it for you.
If the gall takes up a big part of the trunk, you’ll have to take away your complete tree if its progress is extraordinarily stunted.
You can learn more about crown gall in our guide.
8. Pestalotiopsis Leaf Spot
In case you’re questioning, it’s pronounced pesta-low-she-opsis. I didn’t know the phonetics both, till I regarded it up!
Attributable to fungal species within the Pestalotiopsis genus, this illness has distinctive signs: round, necrotic, and black-bordered spots on the foliage.
Contained in the black borders, the spots are an orange to tan hue. Take a better look, and also you’ll discover refined cracking on the floor of necrotic leaf tissues, particularly in older spots.
Usually in spring or fall, spores produced by the fruiting physique of the fungus unfold by way of wind and water, so it pays to observe your watering, particularly throughout cool and overcast circumstances.
Keep away from splashing leaves with irrigation, however in case you do find yourself wetting the foliage, water early sufficient for it to dry earlier than dusk.
This illness is a little bit unpleasant and hinders photosynthesis, so you need to prune contaminated leaves once you see them.
9. Phytophthora Root Rot
Affecting many alternative timber and shrubs within the panorama, Phytophthora root rot isn’t any joke. Not that any of those ailments are, however this one falls particularly flat, humor-wise.
As moisture-loving water molds (oomycetes), Phytopthora species can survive in soil for years, offered that it stays moist.
The causal pathogen spreads primarily by way of water, akin to splashing rain, irrigation, or runoff – however also can journey by way of contaminated soils and backyard instruments.
It favors the cool and wet climate of early spring and late fall, and doesn’t require a wound or different harm to realize entry to plant tissues.
An infection in magnolias causes the foliage to wilt, lose its vibrant coloration, and in any other case seem drought-stressed.
The tree bark at soil degree will usually look unusually darkish, and the wooden beneath it’s going to seem an unhealthy-looking reddish-brown. After a couple of years of declining well being and placing up a struggle, contaminated timber will probably perish.
Guarantee that your soil could be very well-draining previous to planting. In the event you’d like, planting on a raised mound of soil might help hold water from pooling up across the roots. However make it possible for the foundation flare of your magnolia timber are uncovered!
As soon as the magnolia is within the floor and rising, don’t overwater, and make sure you plant in well-draining soil.
If an contaminated tree turns into closely diseased and/or extra hassle than it’s price, take away it – together with the soil throughout the root zone – and substitute it with a resistant tree akin to arborvitae, elm, or ginkgo.
10. Phyllosticta Leaf Spot
A specific foe of the southern magnolia, M. grandiflora, Phyllosticta leaf spot is a fungal situation brought on by Phyllosticta magnoliae.
When a pathogen is called after a plant it infects, that it’s an epic rivalry.
Overwintering on close by fallen plant detritus, the fungus spreads to new leaves in spring by way of splashing water.
On the higher surfaces of recent foliage, small purplish-black lesions type, ultimately rising in measurement and manifesting soiled white facilities whereas surrounded by chlorotic halos of yellow.
As with every leaf spot illness, photosynthesis is diminished and the tree’s well being might endure if the harm is intensive.
Moist, humid circumstances promote illness unfold, so keep away from wetting the foliage and watering late within the day. In the event you discover any noticed leaves, take away them.
If this illness finally ends up infecting a lot of the cover of your magnolia and changing into a much bigger drawback than pruning can repair, early-season functions of copper fungicides might help forestall it and restrict its unfold.
11. Powdery Mildew
It’s kinda good when the identify of a illness lets its signs. Exhibit A: powdery mildew.
In magnolias, the causal fungus is often both Microsphaera penicillata or Phyllactinia corylea.
Spreading by wind in spring to early summer season, the spores trigger white powdery patches to type on higher surfaces of foliage, which may result in curled leaves and stunted progress total.
A specific drawback when days are heat to scorching and nights are cool and dewey, this illness overwinters as fungal mycelium in dormant buds or as spores on fallen leaves.
Correctly prune your magnolia tree cover to permit for airflow to dry the foliage. In the event you discover severely mildewy foliage and branches, lower them straight away.
12. Verticillium Wilt
Relating to killing the one that you love magnolia timber, Verticillium wilt doesn’t waste time. The one time you wouldn’t thoughts a little bit dilly-dallying…
Verticillium wilt kicks off with the invasion of fungal Verticillium species akin to V. albo-atrum or V. dahlia right into a tree’s wounded roots.
You may let you know’re coping with Verticillium wilt by a common browning of the inside sapwood, must you lower away a stem’s bark to have a look.
This an infection clogs up the vascular tissues and results in leaf and department dieback, usually on one facet of the plant.
The stress of the illness permits for opportunistic fungi to invade the tree, tag teaming it into additional decline. In a yr or two, the plant will probably die.
The causal fungi stay in soil and unfold by way of wind, soil disturbance, and gardening instruments.
Burdened-out roots enable for the the pathogen to enter the magnolia, so you’ll want to water correctly – not an excessive amount of, not too little – and watch out to not unintentionally wound the tree with pruning instruments, weed whackers, or runaway garden mowers.
I hate to say it, but when your timber are sick, take away ’em and substitute them with extra resistant timber akin to oaks, conifers, or dogwoods.
13. Wetwood
I guess you’ll be able to guess wetwood’s signature symptom.
Often known as slime flux, wetwood is brought on by the ingress of varied micro organism into tree wounds, primarily these within the roots.
Bacterial fermentation produces gaseous and liquid byproducts, which results in an ooze of darkish liquid from tree crotches, bark cracks, and pruning wounds that reaches its peak in summertime.
This gross liquid additionally strikes inside a plant, inflicting wilting, defoliation, department dieback, and diminished vigor. Fortunately, plant loss of life is a uncommon prevalence.
Apart from avoiding wounds and eradicating severely symptomatic branches, not a lot might be executed about wetwood. It’s kinda just like the runny nostril of magnolia timber, if that’s any comfort.
Aren’t You Sick of Magnolia Illness?
Don’t take heed to Disturbed’s David Dramian and get “Down with the Illness.” They’re your stunning magnolias, darn it! It’s time for motion!
With this information, you’ll be able to hopefully hold your magnolia timber alive and nicely for the lengthy haul.
It might be a problem at instances, however when such attractive vegetation are on the road, issues are positively price addressing. Questions? Random remarks? Time to go to the feedback part beneath!
And for more magnolia-related information, try these guides subsequent: