How to recognize, treat and avoid lilac bacterial blight

CORVALLIS, Ore. – Do new buds and branches on your lilac look blackish, like they’ve been scorched by a blowtorch? Your bush might have a bacterial plant disease called lilac blight.

A cool, wet, rainy, spring season favors development of lilac blight, especially if rains follow a late frost or winter injury. Oregon State University Extension plant pathologists are warning that this might be a favorable year for the disease.

Actually known to plant pathologists by the complete name of “lilac bacterial blight,” this disease is caused by a bacterium Pseudomonas syringae pv. Syringae. The same organism is the source of bacterial blight on pear, blueberry, cherry, maple, and many other woody plants and the symptoms of lilac blight are similar in appearance to fire blight in fruit trees.

At first, leaves look perfectly healthy and then a short time later they look as though someone has placed an open flame near them. The dark black streaks on one side of young shoots show the progression of the disease. The flowers will wilt and turn brown and unopened flower buds become blackened.

Lilac blight is difficult to control and it is recommended that you buy blight-resistant varieties whenever you plant new lilacs.

It also helps to space and prune your lilac plants so they are not rubbing against each other and air can circulate freely between the plants. Do not fertilize late in the growing season. Do not over fertilize young plants because high nitrogen favors disease development, explained Melodie Putnam, OSU Extension plant pathologist.

If your lilac bush does have infection, prune and burn all infected parts as soon as you notice them. A spray of copper sulfate during the early spring each year should help prevent the problem before the buds begin to break.

Lilac blight bacteria over-winter on diseased twigs or on healthy wood. Factors that weaken or injure plants – wounds, frost damage, soil pH, poor or improper nutrition and infection by other pathogens – predispose them to the disease.

Sources of this disease can include old cankers, healthy buds, leaf surfaces and nearby weeds and grasses. Wind, rain, insects, tools and infected nursery stock spread the bacteria.

Some species of lilacs have shown resistance in western Washington including S. josikaea, S. Komarowii, S. microphylla, S. pekinensis, and S. reflexa. Most cultivars of S. vulgaris are susceptible, but some have been observed with less disease when planted in a garden; those include ‘Edith Cavell’, ‘Glory’, ‘Ludwig Spaeth’, and ‘Pink Elizabeth’. Note that ‘Ludwig Spaeth’ is highly susceptible under intense nursery production systems.

The disease starts as brown spots on stems and leaves of young shoots as they develop in early spring. A yellow halo may also be around the spot. Spots become black and grow rapidly, especially during rainy periods. Further infectious development depends on the age of the part of the plant attacked.

On young stems, infection spreads around the stem and girdles it so the shoot bends over at the lesion and the parts above it wither and die. Infections on mature wood occur only on cherry trees, not on lilacs.

Young, infected leaves blacken rapidly starting near the margin and continuing in a wedge-shaped pattern down to the petiole. Eventually the entire leaf dies. On older leaves, spots enlarge slowly. Sometimes, several spots will run together, and the leaf may crinkle at the edge or along the mid-vein. Flower clusters also may be infected and rapidly blighted and blackened. Buds may fail to open or may turn black and die shortly after opening. Symptoms are similar to those of winter injury.

To see photos of this disease, visit OSU Extension’s PNW Plant Disease Management Handbook.

Lilac Bacterial Blight

Overview of lilac bacterial blight

In early spring when the weather is cool and wet, the bacterium Pseudomonas syringae can infect newly emerging shoots, flower buds, and leaves on many lilac varieties, including Chinese, Japanese, Persian, and common lilac.

Lilac bacterial blight symptoms

Symptoms of lilac bacterial blight

Initial symptoms include brown, water-soaked spots on leaves. Spots are initially pin-point in size but can enlarge to 1/8 inch or more. As the disease progresses, spots tend to coalesce, often causing leaves to become miss shapened. Eventually, leaves may be killed. When the infection spreads around a twig, it becomes girdled and dies. This phase of the disease is evident as young new shoots develop in the spring. Shoots turn a black color, droop over, and die.

Disease cycle of lilac bacterial blight

The bacterium Pseudomonas syringae can overwinter in plant debris, healthy tissue, diseased cankers, perennial weeds, and soil. During wet weather in the spring, the bacterium spreads to new growth by wind, splashing rain, insect vectors, or on pruning tools. The bacterium requires a natural opening or wound to cause infection.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents. If your sample is from outside of Iowa please do not submit it to the Plant and Insect Diagnostic Clinic without contacting us

Management of lilac bacterial blight

Buy only disease-free plants. Good sanitation will help prevent the spread of bacteria to nearby healthy lilac plants. Immediately remove and destroy diseased plant parts. Remember to dip your pruners in a 10% bleach solution between each cut. Prune only when the weather is dry and no rain is expected within the next few days.

Sanitation combined with other cultural strategies can provide a good control of lilac bacterial blight. These include spacing or thinning plants to provide for good air circulation and proper watering to avoid wetting of foliage. Also, try to avoid wounding plants as bacteria enter through open wounds.

There are chemical sprays available for lilac bacterial blight; however, these sprays are often not feasible from a homeowner’s perspective. Most chemicals require a full coverage spray before disease appears in spring at an interval of 7-10 days and especially after each rain. Sprays can also cause phytotoxicity in some lilac varieties and does not guarantee complete disease control.

Leaf Curl on Lilacs – Knowledgebase Question

Brown rot fungus can be a problem on cherry trees. Upon inspection of your tree, you’ll probably find other signs, as well. The fungal spores survive on diseased twigs and old, rotten fruits and the spores spread by air currents, rain splash and insects. There’s a gummy ooze associated with the infection, and affected twigs and leaves shrivel and die early in the season. To help control this disease, prune and destroy affected twigs and branches. This pruning will also help open the plant up to good air circulation throughout the canopy. Avoid wetting blossoms, foliage and fruit. Be sure to rake and destroy all fallen fruit and leaves at the end of the season. You can apply a Bordeaux mixture (or other copper-containing fungicide), at budswell to help protect the leaves and blossoms from infection. Apply again after the leaves appear. With preventative sprays and good garden sanitation you should be able to keep brown rot under control.
Lilac leaf curl can be caused by a number of fungal diseases. At this point I would recommend raking to remove the infected leaves and waiting until next spring to apply a preventative fungicide (according to label directions).
Best wishes with your landscape!

Treating Common Lilac Problems: What To Do For Pests And Diseases Of Lilac

Shakespeare memorialized the sweet smell of the rose, but obviously he hadn’t so much as sniffed a lilac, the undisputed perfumed queen of the spring. These beautiful, hardy bushes are a great addition to your landscape because they tend to be easy to care for and the problems with lilac bushes are mostly minor. Even so, it’s best to be prepared if you have a run in with lilac pests and diseases, so we made up a list of common lilac problems you may encounter.

Common Diseases of Lilacs

Although lilacs are a hardy bunch, they can succumb to problems like any other landscape shrub. Be on the lookout for these diseases:

Bacterial blight – The bacteria Pseudomonas syringae causes early shoot and branch dieback, distorted leaves and leaf spots that start out olive green, but soon develop water soaked areas. Those spots turn brown with yellow margins and begin to die. Blossoms may become limp or turn brown suddenly. Pruning away the diseased material and thinning the inside of the shrub is the best way to control this disease, but if the infection is widespread, a copper fungicide will help kill it quickly.

Powdery mildew – Powdery mildew is probably the most common problem in lilacs. It’s caused by a variety of fungal pathogens that result in leaves with a powered appearance, either in tightly organized spots or spread across the surfaces. Increasing the air circulation around infected leaves is the best treatment, so make sure to thin your plants yearly.

Leaf spots – Leaf spots are another fungal problem caused by a variety of pathogens. When you see tan spots appear on your lilac leaves, with or without causing the leaves to fall, you’ve likely got one of the many leaf spot diseases on your hands. As with powdery mildew, this problem is a result of high local humidity, so thin that shrub and clean up all fallen debris to prevent future infections.

Common Lilac Pests

Lilacs attract just a few serious pests, most of the caterpillars and leaf miners that may visit aren’t anything to be worried about. However, if either of these pests appear, it’s time for action:

Scales – Scales can be difficult to detect, many species look like cottony or waxy growths on the stems and branches of landscape shrubs. If you lift their covers though, you’ll find very small, brightly colored insects underneath. Scales are best treated with repeated applications of neem oil, spaced seven to 14 days apart. When they’re clustered together in one section of the plant, pruning them out is an excellent option.

Borers – The larvae of the clearwing moth is a boring insect that prefers to feed on lilacs. These tiny caterpillars spend most of their lives inside the stems and branches of your plant, only emerging to mate. Effective management centers around keeping the lilac healthy and happy, since sick plants are much more likely to attract borers. They have a number of natural enemies that will pick them off when the lilac is stronger and less appealing.

I just planted my lilac bushes and the leaves are curling and turning brown does anyone know why.?

First, make sure your lilacs are in soil with good drainage.

Q.”I just looked at a row of young lilacs with leaves that are turning brown and dying. I know there was a lot of standing water near them for some time, but apparently they were not actually standing in water. I dug up some soil and found it’s still very saturated…” A. “Lilacs are tough, but they don’t tolerate standing water very well.” Too much water in the root zone may manifest these symptoms & can also led to a borer attack. (1) (Good Question & answer site on Lilacs)

I’d be careful & use sanitary precautions, just in case it is bacterial blight, which is common. Prune diseased twigs below twigs & leaves, when the bushes are dry (don’t touch wet leaves). Disinfect shears each time with 10% bleach or alcohol after each cut. (2)

Or… it could be Powdery mildew: “Leaf curling and twisting may be noted before the fungus is evident. Severe powdery mildew infection will result in yellowed leaves, dried and brown leaves and disfigured shoots and flowers.” (3)

Discard the damaged leaves & as a precaution against Powdery Mildew, try a milk/ water solution. “Milk works in two ways: It has a germicidal effect–it kills the fungal spores– and it also appears to stimulate plants in such a way that they become more resistant to the disease. In recent university tests, the milk and water spray was found to be more effective than the two most popular synthetic fungicides on the market today.”

Mix 1 cup of milk with 9 cups of water.

Spray the entire plant twice a week. (4)

Lilac (Syringa spp.)-Bacterial Blight

Cause Pseudomonas syringae pv. syringae, the bacterium that also causes bacterial blight of pear, blueberry, cherry, maple, and many other woody plants. Bacteria overwinter on diseased twigs or as epiphytes on healthy wood. Factors that weaken or injure plants predispose them to disease. Such factors include wounds, both accidental and from pruning or budding, frost damage, incorrect soil pH, poor or improper nutrition, and infection by other pathogens.

Bacterial sources can include old cankers, healthy buds, low populations within plants (with or without cankers), leaf surfaces, nearby weeds and grasses, even soil. Bacteria spread by wind, rain, insects, tools, and infected nursery stock. Mild, moist weather favors disease development.

Two common genetic traits increase the bacteria’s ability to cause disease. Most produce a powerful plant toxin, syringomycin, which destroys plant tissues as bacteria multiply in a wound. Bacteria also produce a protein that acts as an ice nucleus, increasing frost wounds that bacteria easily colonize and expand.

Some species of Syringa have shown resistance in western Washington including S. josikaea, S. Komarowii, S. microphylla, S. pekinensis, and S. reflexa. Most cultivars of S. vulgaris are susceptible, but some have been observed with less disease when planted in a garden; those cultivars include Edith Cavell, Glory, Ludwig Spaeth, and Pink Elizabeth. Note that ‘Ludwig Spaeth’ is highly susceptible under intense nursery production systems.

Symptoms The disease starts as brown spots on stems and leaves of young shoots as they develop in early spring. A yellow halo may also be around the spot. Spots become black and grow rapidly, especially during rainy periods. Further infectious development depends on the age of the part attacked.

On young stems, infection spreads around the stem and girdles it so the shoot bends over at the lesion and the parts above it wither and die. On mature stems, spots usually enlarge along the stem, causing leaf death only within the infected area.

Young, infected leaves blacken rapidly starting near the margin and continuing in a wedge-shaped pattern down to the petiole. Eventually the entire leaf dies. On older leaves, spots enlarge slowly. Sometimes, several spots will run together, and the leaf may crinkle at the edge or along the midvein. Flower clusters also may be infected and rapidly become blighted and blackened.

Buds may fail to open or may turn black and die shortly after opening. Symptoms are similar to those of winter injury.

Cultural control

  • Maintain adequate spacing between plants and prune to provide good air circulation within the canopy.
  • Prune out and burn all affected tissues immediately.
  • Plant resistant species or cultivars.
  • Do not fertilize late in the growing season. Do not over-fertilize young plants.
  • In spring, protect from rain and frost with plastic hoop houses or similar structures. This treatment has been as good as the best chemical method.

Chemical control Focus first on cultural control tactics. Spray before fall rains and again before budbreak in spring. Bacteria resistant to both copper products and antibiotics have been detected in many nurseries. Limit the use of any one group during crop production. Copper products may be phytotoxic when used during the early growing season. Use of anti-transpirants has not been effective.

  • Arbor-OTC is registered for trunk injection, see label for details. Group 41 fungicide (antibiotic). 12-hr reentry.
  • Badge X2 at 1.5 to 2 lb/A. Group M1 fungicide. 48-hr reentry. O
  • Bordeaux (copper sulfate plus hydrated lime) at 4-4-100. An effective combination of products even when bacteria are resistant to copper. Group M1 fungicide. O
  • Champ Dry Prill at 0.67 lb/100 gal water. Group M1 fungicide. 48-hr reentry.
  • Copper-Count-N at 1 quart/100 gal water. Oregon only. Group M1 fungicide. 48-hr reentry general or 24-hr reentry for greenhouse.
  • CuPRO 5000 at 1.5 to 5 lb/A. Group M1 fungicide. 48-hr reentry.
  • Junction at 1.5 to 3 lb/A. Can be more effective than other copper-based products when copper-resistant bacteria are present. Spray solution pH should be above 6.5. Group M1 + M3 fungicide. 48-hr reentry.
  • KleenGrow at 6 to 38 fl oz/100 gal water. 48-hr reentry.
  • Monterey Liqui-Cop at 3 Tbsp/gal water. H
  • Nu-Cop 50 DF at 1 lb/100 gal water. Group M1 fungicide. 48-hr reentry.
  • Phyton 27 at 1.3 to 2.5 oz/10 gal water. Group M1 fungicide. 48-hr reentry.

References Gould, C.J. and W.E. Vassey. 1977. Lilacs resistant to bacterial blight. Proceedings of the International Lilac Society 6:48-57.

Pests And Diseases Of Lilacs

Diseases are always harmful. When lilacs or Syringa shrubs are affected by diseases, it may cause the plants to stop blooming or reduce their number of flowers. In many cases, diseases occurring in the previous year may result in the destruction of the flower buds. In some instances, growers may take preventive or even curative measures. It has often been seen that the lilacs in dry gardens in rural areas are perfectly healthy, while many of those in major cities are vulnerable to a condition known as leaf-roll necrosis. Usually, lilacs grown in places having dry summers and chilly winters are mostly free from diseases compared to those grown in places where the summers are humid and winters are mild.

Like diseases, even problems caused by pests like scales and borers may cause the plants to bear fewer blooms. For instance, Syringa vulgaris or the common lilac as well as several of its cultivars are among the lilacs that are very vulnerable to pest invasions.


Lilac borers These are very niggling pests that are actually the larvae of a wasp-like moth called Podosesia syringae var. syringae, whose wings are semi-transparent and brownish. This pest lays large amounts of eggs in late spring. They usually lay their eggs on the stems of lilac shrubs and ash plants. While they are hatching, the larvae penetrate the branches and are nourished by the wood. Initially, these pests remain out of sight and one notices their presence for the first time when they find the entire leaves on a branch or stem turning yellow and wilting. This usually happens during the spring or towards the beginning of summer. Infestation by lilac borers may cause the bigger branches to become distended and eventually break.
If you take a closer look at such branches, you will notice tiny holes measuring roughly about the size of a pencil lead in diameter at a level of one or two feet (30 cm to 60 cm) higher than the ground. Just below it, you will notice some sawdust. In fact, these holes are actually exit paths of lilac borers and they suggest that the pests have already left, but still some others may be at work. These pests are very visible when you are pruning the plants. In fact, you may even find the borer tunnels breaking through the heartwood, especially of the older branches.
Precisely speaking, stresses as well as wounded plants are most common hunting grounds of lilac borers. They are also common on the bigger and older stems or branches, particularly on the common lilac (Syringa vulgaris). Several pesticides are available in the market to effectively deal with lilac borers. Lilac leaf miners Leaf miners are basically the larvae of a small moth species called Caloptilia syringella. These pests bore tunnels between the leaf layers, thereby giving a blotched appearance to the leaves during the start of summer. Subsequently, lilac leaf miners turn over the leaves and feed on them externally. Eventually, the color of the affected leaves become brown, thereby giving a burnt appearance to the entire plant. When the first sign of leaf miner assault becomes evident, you can soak the leaves with neem or a nicotine spray. However, when you notice the damage, it is already very late to take curative actions. Nevertheless, you should immediately remove the affected leaves and clear the area beneath the shrubs of all leaves and debris during the fall with a view to protect the plants from being infected again. In fact, the damage caused by lilac leaf miners is more aesthetic compared to physiological. S. vulgaris or the common lilac is most vulnerable to invasion by leaf miners. Mites Lilacs are often susceptible to the eriophyid mite (scientific name Aculus massalongoi). This pest creates a rust or silver color on lilac leaves and may sometimes result in leaf-rolling. Oyster shell scale These are very bizarre looking insects that appear as flat, oval-shaped and lifeless lumps. While shielding themselves under a wax-like coating and scales actually damage the plants by pulling out their fluids. These pests lay eggs on lilac shrub/ tree barks either during fall or in spring. These eggs are hatched later in spring. The young scales are mobile and have a light yellow or orange hue. They measure roughly 0.1 inch (2 mm) in length. The legs of these pests wither when they settle on a place to feed. When you are pruning the stems of lilacs, you may possibly notice that the stems have become roughened and have an unusual gray and dry appearance. When you take a closer look at the stems, you will notice minute bumps that can be skimmed using your fingernail or the pruning shears’ blade. Lepidosaphes ulmi This type of scale is known as the apple mussel scale and you can control their infestation on lilac plants by pruning the branches that have been infested heavily. In the next spring, you should apply a dormant-oil spray before the emergence of new leaves. You need to undertake this treatment prior to the bud break and essentially on an arid, sunlit, mild morning. In order to avoid harming the lilac plant, ensure that you do not apply the dormant-oil spray when the temperature is below 39°F (4°C) or 48 hours before or after a frost. Preferably, you should undertake the treatment on a calm morning when there no frost is anticipated that night and the atmospheric temperature is over 60°F (15°C).

You can also eliminate scale by painting the lilac branches with a solution of lime-sulfur using a paint brush. Alternatively, you can directly spray a soap water solution on the plants to kill scale. Add one teaspoon (5 ml) of any liquid dish soap that is additive free (such as Ivory) to one quart (1 liter) water and spray the solution on the plants. In fact, the soap water solution is most effectual when sprayed in the later part of spring or the beginning of summer – the time when these pests are in the crawler stage. Continue spraying the soap solution till the foliage seeps.

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Blight Usually, you will notice the first symptoms related to bacterial blight (scientific name Pseudomonas syringae var. syringae) right in the start of the season – either when the weather is hot and humid or immediately after the spell. The beginning of this bacterial disease may often be remarkable. All of a sudden, the leaves start appearing as if they have been scorched all along their edges, and subsequently the stems become black. Bacterial blight may also result in formation of black spots confined by a pale circle on the leaves. When this disease affects plants, their flower clusters first wilt and eventually die. This bacterium also infects other plants including cherry, pear, maple and many varieties of ornamental plants.
There is a different kind of blight, which is attributed to a fungal infection. This disease is caused by Ascochyta syringae and the symptoms of this plant disease are same as those caused by bacterial blight. The disease starts from the soil and spreads up when the soil is damp during the start of spring. While these diseases do not essentially kill the plant, but they make the lilac appear unattractive and ugly. Moreover, these blights can also damage the new growth. These also affect the blooms adversely and the blooms may be lost in the year of the infection or the subsequent, subject to the time of the bacterial or fungal infection.
Usually, it is very difficult to control blights. In fact, plants that have been damaged in some way and the new growths are most vulnerable to these diseases. In order to reduce damage caused by frost keep the foliage dry, ensure that the plants are well ventilated. If it has been found that maximum damage caused by blights is in the low-lying areas – places where cold, moist air collects easily. If you notice blight soon after the plants are infected, cut down all the infected parts and remove them as soon as possibly so that they do not spread to the healthy areas. Moreover, you always need to sterilize the saw or pruning shears between cutting different parts by wiping their edges with Lysol, alcohol or a home-made solution of one part domestic bleach and 10 parts of water.
In the following year, spray the plants with a copper fungicide while the weather during spring is still warm – a favorable time for infections. Do not undertake heavy pruning or feed the plants with too much fertilizers, as these promote fast, but weak growth. It has been found that the common lilac (S. vulgaris) and other lilacs like S. x hyacinthiflora that bloom early are most vulnerable to blights. Compared to the doubles, the singles are more susceptible. Similarly, lilacs that bear purple, magenta and blue blooms are more vulnerable to blights compared to those that produce lilac hued flowers. In addition, lilac species like S. villosa and S. x prestoniae are very susceptible to these diseases. However, lilac species as well as cultivars that bloom late in the season are able to resist blights to some extent. Mycoplasma This prokaryotic microorganism causes a disease known as witches’-broom, which is widespread in large varieties of lilacs compared to the shrubs grown in the backyard. This disease is manifest in the form of a clump on very thick growth on any common lilac shrub or tree. This disease was noticed for the first time in 1951 and till date remains to be rather mysterious. However, scientists have come to know that a pathogen similar to viruses and called MLO (mollicutes or mycoplasma-like organisms) witches’-broom. It seems that, these microorganisms form colonies in the phloem (sap) and disturb the flow of the sap, thereby killing a new growth point. This, in turn, leads to thick growth of shoots on the side of the plant – generally in the lower part of the plant.

It has been found that S x. prestoniae and S. x josiflexa, lilacs that flower later in the season, are more vulnerable to this disease. Initially, the affected plant may appear unhealthy, its growth may be twiggy (fleshless) and it may produce unusual bloom out-of-season or have growth flushes. Eventually, the plant dies. Ash trees are affected by a comparable disease that is called ash yellows. This disease may also affect vigorous lilac plants and may also spread to ash trees possibly through an insect. In order to prevent the plants from being infected by this microorganism and also treating the affected plants, it is important to prune them with tools after sterilizing them properly. For instance, you may wipe or dip the blades of the pruning shears, knives and cutters in Lysol, alcohol or a home made sterilizing solution prepared by adding one part domestic bleach to 10 parts water before pruning or cutting a plant. As of now, there is no cure for this disease. As soon as you notice a plant affected by this disease, remove the plant and destroy it immediately. Powdery mildew This is a fungal plant disease caused by Microsphaera alni, M. syringae. This disease attacks lilacs when the atmospheric condition is warm and humid. Generally, this fungus first attacks the older leaves that are towards the plant’s base some time in July and then spreads all over the foliage between the period mid-August and October, when the leaves fall. First the leaves develop ugly white or pale gray blotches, which gradually change to yellowish and eventually the leaves drop from the branches. When this disease affects plants, the growth of new leaves is also stunted. In most cases, the harm done to the plant is more aesthetic compared to physical. This is because the plant looks ugly. On the other hand, the leaves generally drop off at a time when they have already accomplished their tasks.
In fact, you can provide the plants with best protection right at the time of planting them. Provide your favorite lilacs with total sunlight and proper ventilation. In addition, you should preferably select species and cultivars that are hardy. Water the plants deeply by supplying the water right on the ground and not the plant. Majority of the cultivars as well as hybrids of S. vulgaris or the common lilac are vulnerable to this disease. Lilacs that are worst affected by powdery mildew include “Henri Martin”, “Mrs. W. E. Marshall”, “Buffon”, and “Marlyensis”. In addition, the variety called S. x chinensis “Metensis” is also very vulnerable to this disease. If you notice a tendency of your lilacs being infected by Microsphaera alni, you should grow the plants at the back of perennially growing plants like lilies as well as ornamental grasses, whose height conceal the disfigurement of the lilacs. Some of the lilac species that possess the aptitude to resist this fungal disease include S. emodi, S. meyeri, S. x diversifolia, S. yunnanensis, and S. x persica. Virus Ring spot is a viral disease that causes yellow or target marks on lilac leaves, which drop from the plants untimely. Eventually, the affected plants die. Since there is no cure for this disease, you need to destroy the diseased plants. Wilt While lilacs are seldom affected by verticillium wilt, this disease may affect plants of this genus when they are growing in soils where people earlier grew potatoes, tomatoes or eggplants. When grown in such soils, lilacs will die sooner or later. Hence, you need to remove the plants to a suitable location before it is too late. In fact, it is difficult to control wilt. Therefore, decide on a suitable place before planting your favorite lilacs. Lilacs

Botanical lilacs
Growing garden lilacs
Lilacs in containers
Renovating and moving lilacs
Pruning lilacs

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From Joan Sullivan – Oct-04-2016 I had something on my lilac tree bark that looked like white powder. After taking a photo and zooming in, I could see that it was not powder but millions of individual “scales”. It spread from one lilac tree (about 3 years old) to the one right beside it. After much research, I was able to identify it as White Prunicola Scale. It had overtaken the trunk and branches, and with no “sure cure or treatment” for this advanced stage, we felt it best to remove the trees.

Lilac Tree Disease

lilac flower on a tree with sky image by Piter Pkruger from

Lilac trees are a lot like lilac bushes, except, of course, a great deal taller. A lilac tree may grow to 30 feet in height. They also have a rounded shape and great clusters of blossoms that bloom on the sides of the branches in beautiful white, violet, lavender and deep purple spikes. While lilac trees are relatively disease-resistant, they do take a long time to recover when they experience stress. They may stop blooming altogether in some cases. For this reason, you must be alert with your lilac tree so that you can target any disease-related problems before they place serious duress on your plant.


Several types of disease affect lilac trees. Lilac blight, mycoplasma and powdery mildew are common lilac disease problems. Ring spot virus can also infect lilac trees as well as lilac bushes, and in rare cases lilac wilt can also affect lilac trees, depending on where they are planted.


Symptoms of lilac tree diseases tend to be characterized by their visual effects on the tree. For example, leaves may appear scorched and brown around the edges. They may also develop a variety of dark rings and spots. Flowers also tend to wilt and die. Additionally, some diseases cause a white, black or gray substance to take over the plant, spreading along branches and onto leaves and flowers. You may also notice that parts of your plant are turning black or have developed large, lumpy growths.

Diagnosing the Problem

Once you have identified your lilac tree’s symptoms, you need to diagnose the problem so that you can establish a treatment plan. Lilac blight is generally characterized by scorched-looking leaves and blackened shoots. In short, the young growth on your lilac tree will be dying. Mycoplasma (also called witches broom) creates large, lumpy masses on the branches of lilac trees, while powdery mildew, true to its name, is characterized by a grainy film of gray, black or white that spreads along leaves, branches and flowers. Ring spot virus causes yellow rings on the leaves of the plant, while lilac wilt causes sudden, abrupt wilting usually only on one side of the plant.

Treating Your Lilac Tree’s Disease

Some types of lilac tree disease are untreatable, and your only option is to remove the plant before other plants around it are infected. Ring spot blight and lilac wilt are both untreatable. Powdery mildew will usually run its course without seriously damaging the tree and without too much damage to the beauty of your plant because it generally strikes after the tree is done blooming for the season. However, without a fungicide treatment, it will happen again at the end of the next season. If your tree develops mycoplasma or lilac blight, you will need to remove the affected portions of the plant. Be sure to dispose of them in garbage bags rather than dropping the pieces on the ground or in a compost pile, and sterilize your pruning shears with rubbing alcohol each time you make a new cut. This should bring these diseases under control without killing the plant.

Preventing Lilac Tree Disease

Lilac trees need plenty of sun and air circulation. This helps prevent nearly all infections. Additionally, make sure that you do not plant your lilac tree in an area where eggplant or tomatoes grew previously. These plants leave fungal organisms in the soil that lead to lilac tree wilt and can kill your lilac tree.

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