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.
How is bacterial blight on lilacs treated?
Portland, Oregon – Do the fresh blooms and branches on your lilac plant resemble burnt wood from a blowtorch? Lilac blight is a bacterial plant disease that could affect your bush.
Lilac blight is more likely to occur in a cool, wet, rainy spring, especially if there has been a late frost or other winter damage. Plant pathologists at Oregon State University Extension are cautioning that this year may be favorable for the disease.
Lilac bacterial blight, as the disease is officially known to plant pathologists, is brought on by the bacterium Pseudomonas syringae pv. Syringae. The bacterial blight that affects pear, blueberry, cherry, maple, and many other woody plants is caused by the same organism, and the symptoms of lilac blight resemble those of fire blight in fruit trees.
Initially, leaves appear to be in full health, but a short while later, they appear to have an open flame nearby. Young shoots with dark black stripes on one side demonstrate the disease’s progression. Unopened flower buds turn black and the blossoms fade, turning brown.
Never fertilize after the growing season has ended. Don’t fertilize young plants excessively.
Lilac blight is challenging to eradicate, therefore anytime you plant new lilacs, it is advised that you use blight-resistant kinds.
In order to prevent friction and allow air to easily circulate between the plants, it also helps to space and clip your lilac plants. Never fertilize after the growing season has ended. Melodie Putnam, an OSU Extension plant pathologist, advised against overfertilizing young plants since excessive nitrogen levels encourage the development of diseases.
If your lilac bush does have an infection, immediately cut and burn all affected areas. A copper sulfate spray applied in the early spring each year should help stop the issue before the buds start to open.
In order to prevent friction and allow air to easily circulate between the plants, it also helps to space and clip your lilac plants.
Bacteria that cause lilac blight can overwinter on good wood or sickly twigs. Plants are more susceptible to the illness when they are weak or injured by factors such as wounds, frost damage, soil pH, inadequate or poor nutrition, and infection by other diseases.
Old cankers, healthy buds, leaf surfaces, and adjacent weeds and grasses can all be sources of this disease. The bacteria were dispersed by wind, rain, insects, tools, and diseased nursery stock.
In western Washington, some lilac species, including S. josikaea, S. Komarowii, S. microphylla, S. pekinensis, and S. reflexa, have demonstrated resistance. The majority of S. vulgaris cultivars are prone to the illness, however others, like “Edith Cavell,” “Glory,” “Ludwig Spaeth,” and “Pink Elizabeth,” have been seen to be less afflicted when grown in gardens. Be aware that ‘Ludwig Spaeth’ is quite vulnerable in systems with large nursery production.
If your lilac bush does have an infection, immediately cut and burn all affected areas. Early in the spring, apply copper sulfate to the ground.
As young shoots form in the early spring, the disease first appears as brown blotches on their stems and leaves. The area may also have a yellow halo surrounding it. Especially when it rains, spots quickly turn dark and spread out. The age of the plant component that was damaged determines how far the infection can spread.
On immature stems, the infection encircles and girdles the stem, causing the shoot to crook at the lesion and the sections above it to wilt and die. On mature wood, lilac trees do not get infected; only cherry trees do.
Young, infected leaves quickly become black, first at the margin and then down to the petiole in a wedge-shaped pattern. The leaf eventually withers completely. Spots on older leaves slowly grow. The margin or the mid-vein of the leaf may crumple when numerous areas occasionally run together. Additionally, flower clusters may become diseased, quickly blighted, and darkened. Buds may not open properly or they may turn black and die soon after they do. The signs are the same as those of a winter injury.
Visit the PNW Plant Disease Management Handbook of OSU Extension to view pictures of this disease. The guideline reiterates the following cultural restrictions on treatment:
- Maintain proper plant spacing and prune to encourage proper airflow within the canopy.
- Cut all afflicted tissues out and burn them right away.
- Plant species or cultivars that are resistant.
- Never fertilize after the growing season has ended. Don’t fertilize young plants excessively.
Do you want to know more about this subject? View further materials from OSU Extension here:
Why are my lilac plants’ browning and curled leaves?
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.
What does a lilac shrub look like when it is overwatered?
Overwatering your lilacs is one of the worst things you can do. If the soil around a particular lilac variety is always wet, then all lilac kinds are susceptible to fungal diseases including mildew, mold, and other sorts of fungi.
- If lilacs are overwatered, mold and fungus can harm them.
- Lilacs that receive too much water may have root rot.
- Your lilacs have received too much water if their leaves are yellow, pale, or withered.
- If your lilacs have been overwatered, let the soil dry to a depth of 34 inches (7.510 cm) before providing additional moisture.
Lilacs that receive excessive water risk developing root rot. A lot of the time, wilted, pale, or yellow leaves indicate an excess of water. Reduce watering to once every 14 days until these symptoms go away if any of these things happen or if the ground appears to be persistently damp. Remember that you might not need to water your lilacs at all if you are experiencing regular rains.
How can a lilac shrub be brought back to life?
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.
How can lilacs show signs of bacterial blight?
Gina Foreman* and Brian Hudelson, UW-Madison Plant Pathology *Fulfilled in part the criteria for the Plant Pathology 875Plant Disease Diagnostics Clinic Internship.
Describe the bacterial blight. A common and frequently deadly disease of Chinese, Japanese, Persian, and common lilacs as well as walnut, apple, pear, plum, and cherry is bacterial blight, commonly known as blossom blight or shoot blight. The disease is most likely to affect common lilac cultivars with white flowers.
What appearance does bacterial blight have? Initially, dark brown necrotic (dead) leaf patches with yellow haloes could be a sign of bacterial blight. Leaf bending and twisting may occur if leaf spots appear before leaves have fully developed. Necrotic blotches that begin at the leaf borders and move within are signs of a more advanced condition, as are black streaks on twigs. Bacterial blight can cause the death of branch tips, leaves, and blooms in its most severe form.
Where is the origin of bacterial blight? The bacterium Pseudomonas syringae pv. syringae (Pss), which thrives in damaged stem tissue (cankers), plant detritus, and soil, is responsible for bacterial blight. Pss is distributed more frequently by wind and rain than by insects or by pruning instruments. Pss frequently lives on the surface of healthy plants without harming them. The bacterium can cause infections when it enters tissue naturally or by wounds brought on by insects, pruning, wind damage, or hail.
How can a plant that has bacterial blight be saved? Dispose of sick branches by burning or burying them after cutting them off 10 to 12 inches below the point of noticeable symptoms. Always prune in dry weather, and after every cut, disinfect pruning shears by putting them in a 10% bleach solution or alcohol for at least 30 seconds (spray disinfectants that contain at least 70 percent alcohol can also be used).
How can I prevent bacterial blight issues in the future? Lilacs should be planted with sufficient space between the shrubs. Each winter, thin individual shrubs to encourage proper airflow (see UW Garden Facts XHT1015 for pruning tips). To prevent stress that could make shrubs susceptible to disease, properly fertilize, water, and mulch them. Avoid watering overhead because it can keep the leaves damp. You might want to use a mixture of copper- and mancozeb-containing fungicides to reduce bacterial blight if you’ve experienced issues. Fungicides should be applied twice to three times, seven to ten days apart, as leaves emerge but before symptoms appear. To ensure that you use the fungicide in the safest and most efficient way possible, make sure to read and adhere to all label directions.
What appearance does bacterial blight have?
Common bacterial blight first manifests itself on leaves as tiny, wet spots, bright green areas, or both. The tissue in the middle of these spots degenerates and turns brown as they get bigger. These irregularly shaped patches have a lemon yellow ring around them, which can be used to identify frequent bacterial blight. On the margins or interveinal regions of leaves, patches or lesions form. The spots could develop together, killing the entire leaf and defoliating the plant if that happens.
Infected pods will have tiny, wet spots that grow into larger, irregular, dark red blotches, occasionally with a yellow slimy ooze. Common and halo blight illnesses’ pod symptoms are nearly same (see photo comparison). Infected pods can spread to the seeds inside. When infected, white seed may develop butter-yellow blotches. Seed that has been severely contaminated may be shriveled and gerinate poorly.
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.