Lilacs are a sturdy group, yet they are susceptible to issues just like any other landscaping shrub. Keep an eye out for these illnesses:
Infection blight
Early shoot and branch dieback, deformed leaves, and leaf spots that start out olive green but quickly turn into water-soaked patches are all brought on by the bacteria Pseudomonas syringae. These areas start to deteriorate and turn brown with yellow edges. Blossoms may abruptly grow limp or turn brown. The easiest strategy to control this illness is to remove the infected material and thin out the shrub’s interior, but if it has spread widely, a copper fungicide will hasten its demise.
a powdery mold
The most frequent issue with lilacs is most likely powdery mildew. It is brought on by a number of fungal diseases, which make the leaves to look powdery, either in discrete areas or all over the surfaces. The best therapy is increasing airflow around sick leaves, so thin your plants annually.
Leaf spotsLeaf spots are another fungus issue that can be brought on by numerous infections. You probably have one of the various leaf spot diseases on your hands if you notice tan spots developing on your lilac leaves, whether or not this results in the leaves falling. This issue, like powdery mildew, is brought on by excessive local humidity; therefore, thin out that shrub and clear away any fallen debris to stop more infections.
Fungal diseases
This season, the Lilac Pseudocercospora leaf spot, a fungus, was detected in lilac samples examined by the Plant Disease Clinic. The same symptoms have been recorded (yellowing then browning leaves, dieback).
The PDC places a strong emphasis on sanitation because it appears that Pseudocercospora spores can survive on plant detritus for a number of years (leaves, stems, dead flowers, bark).
- To assist lessen the possibility of reinfection the next season, remove fallen leaves.
- Consistent watering and renewal cutting to reduce density will sustain the stressed plant.
Several of the plants in our landscapes, including lilacs, are afflicted by verticillium wilt. Verticillium dahliae and Verticillium albo-atrum are the two fungi that cause it. For a plant with this fungus infection, there is no cure.
- As a result of the fungi clogging the branch’s vascular system and preventing the transfer of water and nutrients, individual branches turn brown and die quickly.
- To increase plant longevity, increase watering and fertilization.
- The disease can spread across all sections of the afflicted plant, thus the best preventive is to buy resistant cultivars and practice proper hygiene.
Insects
The Lilac Borer, sometimes known as the Ash Borer, is a clearwing borer moth that creates tunnels in lilac stems.
- Frass, sap, and sawdust are warning signs (excrement).
- Some plants can withstand this harm.
- Others see branch dieback, and occasionally the entire plant dies.
- They won’t likely catch anyone’s attention.
Jeff Hahn, an extension entomologist, confirmed that no lilac borer samples have entered his lab this year.
Herbicide damage
Broadleaf weed treatments on lawns may volatilize, changing to a gas, and float onto unintended plants if sprayed during periods of extreme heat and humidity.
Herbicide damage signs like cupping and browning would appear in patterns:
- along a hedge’s one side but not the other,
- bushes positioned in or close to lawn areas, at the same level throughout their bases,
- and most critically, away from the area’s predominant winds.
Lilac hedges next to agricultural fields or other sizable herbicide-treated areas may experience damage in this manner.
How is a lilac bush revived?
You might believe your lilac is dying if you see it becoming a little frail or worn out, or if it only produces a few little flowers in the spring. Often, all a plant needs to produce robust new growth and abundant, fragrant blossoms is some hard pruning and some feeding. Rejuvenate a lilac bush by working with it just after bloom, when the blooms have dried up and are spent.
To get to the grass or soil layer, rake away any debris, dead branches, or fallen leaves from the lilac’s base.
Pick three to five of the lilac’s strongest branches after surveying the entire plant. Follow the branches you’ve chosen to the plant’s base, where you can flag each sturdy branch by gently tying a rope or ribbon around its base.
Use hand pruners or a handsaw if needed to make a clean, horizontal cut across all of the unflagged branches that are about an inch off the ground. To prevent breaking off any limbs you want to maintain, carefully pull the trimmed branches away from the lilac.
- You might believe your lilac is dying if you see it becoming a little frail or worn out, or if it only produces a few little flowers in the spring.
From the remaining branches, take off your sting or ribbons. Fertilize the lilac around its base according to the dosage and application guidelines provided by the manufacturer.
Mulch should be applied in a ring around the lilac’s base that is no deeper than 3 inches and no wider than 3 feet. New sprouts won’t be able to emerge if the mulch is too deep.
If there is a drought or excessive heat in your area during the summer, make sure the plant is well-watered. Lilacs require good drainage, but they don’t fare well in dry soil.
The next spring, watch for buds to start swelling on the branches. Reapply fertilizer right before flowering and once more after flowering is finished. This is how you should fertilize each year.
- From the remaining branches, take off your sting or ribbons.
- The next spring, watch for buds to start swelling on the branches. Reapply fertilizer right before flowering and once more after flowering is finished.
Maintain your lilac by doing minimal annual pruning to remove wasted flowers and only every three to five years to remove old and dead branches.
Avoid letting the feed come into contact with the branches when applying fertilizer to the area around the plant, whether it be granular or water-soluble.
Why does my lilac shrub appear to be in trouble?
- Lilac shrubs die because of a fungus brought on by poorly draining soils. Lilacs need well-draining soil to thrive, and if their roots are in soggy soil, they are vulnerable to root rot and other fungi that can kill the branches and turn the leaves brown.
- If the soil is too dry, newly planted lilac plants may wither and die. For lilacs to flourish, the soil must be evenly moist but also have good drainage. The roots cannot absorb enough moisture if the soil is too dry or too sandy, which causes the leaves to wilt and appear to be dying.
- Lilacs thrive in open spaces with direct sunlight. If the lilac is placed in a shaded garden, it will grow slowly, produce fewer flowers, and its leaves may turn yellow and look to be dying.
- Lilacs are indigenous to the Balkan peninsula and usually flourish in soils with a pH of either neutral or alkaline. The lilacs’ roots cannot absorb some nutrients if the soil is excessively acidic, which results in the leaves turning brown and yellow, poor growth, and a withering appearance.
- Lilacs thrive in cold winter areas with little humidity, and they do best in gardens in USDA zones 3 through 7. In contrast to the conditions to which the lilac has adapted, a winter that is too mild or a climate that is constantly humid leads to fewer blossoms, poor growth, and a higher risk of fungal diseases.
- Lilac borers are insect larvae that manufacture sawdust and make tiny holes in the wood of lilac plants. Lilac borers cause the stems to die and break off, and the leaves to droop.
- Create the conditions of a dying lilac’s natural environment by relocating it to soil that is well-draining but maintains moisture, has an alkaline soil pH, and is in full sun in order to save the lilac. To encourage new growth, prune any decaying branches all the way back to the trunk. Apply lindane spray if there is evidence of lilac borers.
How is bacterial blight on lilacs treated?
Are the stems and leaves fading to black? Perhaps the stems have a shepard’s crook-like droop to them.
These are all signs that the bacterial blight on your lilac plant is present.
It appears that the conditions were right for this sickness to emerge this year. Frost damage was brought on by snow and freezing conditions in the middle of April, just as the lilac leaves and flower buds were beginning to emerge. We have the ideal environment for this sickness when you combine that with the spring’s chilly, damp weather.
Pseudomonas syringae, often known as bloom or shoot blight, is the bacterium that causes lilac bacterial blight. All varieties of lilacs, including Chinese, Japanese, Persian, and our common lilac, are susceptible to it (Syringa vulgaris).
Some lilac varieties, such as Syringa patula “Miss Kim,” “Superba” Littleleaf Lilac (Syringa microphylla), and dwarf Korean lilac, have demonstrated resistance to this disease (Syringa meyeri).
Only a small number of common lilac varieties, including “Sensation,” “Krasavitska Moskvy,” “President Grevy,” “Edith Cavelle,” and “Victor Lemoine,” have demonstrated resilience.
Lilac blight presents with signs that resemble those of frost damage. Emerging leaves, floral buds, and new shoots are all vulnerable.
On leaves, symptoms first appear as tiny, pinpoint-sized water-soaked patches. It’s possible to see a yellow halo surrounding the area.
Rapid blackening of leaf margins creates a characteristic wedge-shaped pattern all the way to the petiole. If spots begin to appear before the leaves have fully opened, the leaves may twist and curl.
Lilac blossoms may also carry an infection. Flower buds that are infected may not open, or they may open but turn black and die.
The disease appears as small brown patches that quickly spread, especially on stems and twigs when there has been a lot of rain. Infected twigs may get girdled, become black, topple down, and succumb.
The spring is when this is most obvious. This resembles fire blight in apples if you are familiar with such diseases.
Toxins made by the bacterium Pseudomonas syringae injure the lilac cells. To infiltrate the plant tissue and spread infection, it requires a wound or other natural opening.
Plant stress is linked to lilac blight. Infected plants are those that have been injured, have endured previous droughts, or may have received inappropriate fertilizer.
The basic suggestion for preventing lilac blight is to get rid of all diseased material. 10 to 12 inches below the obvious infection, prune diseased branches.
Only prune during dry, sunny conditions to reduce the spread to fresh cuts. Between each cut, disinfect pruning implements with a 10% bleach solution to prevent the spread of the bacteria.
Infected plant matter ought to be thrown away or destroyed, not composted or piled on top of other vegetation.
Lilacs should be separated from one another to avoid touching. Pruning elder plants. Lilacs should be pruned to promote good airflow within the canopy and between individual plants so that rain-soaked leaves can dry out fast.
Don’t prune in the spring. Lilacs should be pruned as soon as their flowering season is through.
Late in the growing season, avoid fertilizing lilacs. High nitrogen levels encourage the growth of succulents, which are more prone to illness.
Look for resistant species or cultivars when purchasing new lilacs. If you are establishing fresh lilacs, stay away from watering the foliage.
Numerous locations, including healthy plant tissue and plant waste like fallen leaves, are suitable for this bacterium to overwinter. It may also hibernate in the soil around your lilac plant or in perennial weeds.
The scale of your lilac may make it impractical for a homeowner to perform the spraying. One suggestion is to spray copper sulfate in the early spring to ward off illness.
Since copper fungicides are preventative rather than curative, they would need to be applied before symptoms materialize.
as the leaves begin to develop, two or three times every seven to ten days.
The lilac bush would have to be entirely covered. Be aware that some pollutants might make some lilac cultivars poisonous.
A broad spectrum biofungicide called Serenade Garden is approved for use against Pseudomonas species. According to the current label, it may be applied to treat lilacs either before the foliar illness manifests itself or at the first sign of infection.
Another suggestion would be to apply a copper fungicide in September that is designated for lilacs and blight and to repeat the application just before the start of the fall rainy season. It might not happen the following spring thanks to this. Lilac blight cannot always be completely controlled with spraying.
Follow all label directions for managing the insect or illness in question when using any pesticide.
When visiting the Cornell Cooperative Extension office, kindly don a mask and sign in at the front desk.
Traditional in-the-ground gardens can be replaced quite well by raised bed gardening. For small yards or novice gardeners, they are extremely practical.
The fundamentals of building a raised bed, site selection, creating a soil mixture, and imaginative planting concepts will all be covered by Master Gardener Brandie W. It’s a no-cost event.
Many gardeners struggle with the “hell-strip,” or the space between the sidewalk and the street. Most are sparse, weed-filled areas that suffer from winter road salt and summer soil that has been baked and dried.
Find out how to avoid common hell strip traps so you may turn yours into a beautiful garden. The course is without cost.
Why are the brown and curled-up lilac leaves on my plant?
The leaf miner insect and certain illnesses, such powdery mildew, are two of the most frequent causes of curled lilac leaves, however there are many other potential causes as well. It might also indicate that your lilac bush isn’t getting enough sunlight or water.
Curled leaves may indicate something that won’t ultimately harm the plant, but you can never be sure. This is the dilemma. This is why applying a pesticide or fungicide may be quite beneficial, since doing so will help the plant recover from any diseases it may have and enable it to develop robustly and healthily.
Once more, it’s critical to identify the issue as soon as possible because illnesses like powdery mildew can develop slowly at first but swiftly spread, which means your lilac shrub could perish without your knowledge.
In other words, curled leaves on a lilac bush are not always merely a cosmetic problem; they can also be a sign of far more significant problems. This includes ailments that could ultimately result in the plant’s death, therefore acting sooner rather than later is always the best course of action.