Viburnum leaves turn brown due to Sunburn. If you see brown spots on Viburnum leaves, it is due to Fungal leaf spot disease. Viburnum leaves could also turn brown due to Mildew diseases.
Viburnum is a genus of ~150 plants that are grown in gardens for their beautiful flowers. These plants give out colorful flowers.
Viburnum plants give out pretty-looking foliage. Their fruits are edible and the plant will be a great addition to your garden.
Why are my Viburnum leaves turning brown?
Fungal leaf spots begin as small spots but enlarge and become reddish/brown spots. These spots are angular/irregularly shaped. Viburnum leaves turn brown when the plant is severely infected by Powdery mildew/Downy mildew diseases.
Fungal leaf spots
Fungal leaf spots are common in a large number of plants. They are caused by fungal pathogens. There are various types of fungi that cause leaf spots.
These leaf spots start off as small, red/dark purple spots. These small spots soon enlarge and are seen commonly along the veins.
Soon the spots are bordered with dark brown colored circles. The pathogen eats away the tissue in the center of the spots.
Fungal leaf spots usually occur in warm, wet months. You can prevent this disease by carefully watering only the bottom of the plant and not the leaves.
To control leaf spots in Viburnum
- If you think the plant is severely affected, destroy the plant and plant parts carefully to prevent a large-scale infestation.
- Make sure you’re not watering the leaves of the plant. Wet leaves harbor and encourage fungal growth.
- Group M1 fungicides can be used to control fungal leaf spots effectively.
Even Anthracnose can cause brown spots on the leaves of Viburnum. You can prevent these leaf spot diseases by keeping the leaves dry as the pathogens spread via moisture.
You can use fungicides that are available commercially to control the leaf spot infections in Viburnum.
Mildew in Viburnum
Viburnum plants are often infected with Powdery mildew/Downy Mildew diseases. These diseases are caused by fungal pathogens.
Mildew diseases are especially seen in moist weather when the leaves are wet for a long duration.
Powdery mildew causes a powdery layer on the leaves of the Viburnum plant. Leaves of the severely infected plants turn brown and fall off.
Downy mildew is caused by a fungus-like pathogen. It spreads rapidly from the infected plants to the other plants in the garden.
Downy mildew infected plants’ leaves initially turn yellow or translucent. Eventually, as the disease progresses, the leaves turn brown and die.
To treat
Spray the infected plants with fungicides that contain horticulture oil. All the actions that you take to treat leaf spot diseases work well to treat Mildew.
Viburnum leaves drying up
Viburnum leaves get dried up due to sunburn. The leaves will turn brown and they look completely dried up.
Leaf scorch or sunburn occurs when shade-loving plants get exposed to full sun. As you can expect this mostly happens in the summer months.
Sunburn causes brown marks on the leaves. Viburnum thrives in partial shade. You may want to arrange this in summer.
To provide shade to your Viburnum plant you can plant a sunburn-tolerant plant nearby. Alternatively, you can also set up artificial shade.
Viburnum branches dying
Whole branches of Viburnum die of Botryosphaeria canker disease. This disease is caused by a fungal pathogen.
Entire branches wilt and die due to this canker. The fungus produces some fruiting bodies that turn up on the bark. They appear black in color.
These fruiting bodies enter the cambium via any injury that the plant has. Cankers form girdles as they devour cambium and stop the water and nutrient supply.
To treat
It is ideal to prevent any disease rather than trying to treat it. This is an opportunistic pathogen and infects only stressed-out plants.
Do not ever let your plants run into drought stress. Cut and dispose of the infected leaves of the plant. There is no way to treat this disease.
Just let the plant gain back its vigor. Nurture the plant carefully and it should bounce back healthy.
Leaf rust in Viburnum
If the leaves appear rusty instead of brown, then the plant is probably suffering from rust disease. Rust disease is caused by fungi.
Viburnum leaves that are infected wither and die. Leaf rust is a contagious disease so you need to make sure it doesn’t spread across your garden.
Dispose of the infected leaves carefully and sanitize the garden tools after use. Destroy diseased plants in spring.
Dog urine
The viburnum plant’s leaves also turn brown if a dog urinates on them. If this is the case with your Viburnum plants, try to build a barrier that keeps dogs away from your precious plants.
Male dogs usually do this to mark their territory. I saw this happen in many gardeners’ homes. So, watch your dog’s movements carefully the next time he is in the garden.
Viburnum leaves curling and turning brown
Viburnum leaves curl and turn brown when the plant is exposed to high temperatures. The leaves become dry, and wrinkly, and fall off the plant.
The maximum temperature Viburnum can tolerate is from 70~85℉(21~30℃). Mist your plant occasionally to help the plant survive on a hot day.
Give the plant some shade if it gets too much sunlight in the afternoon. You can control temperatures more efficiently if the plant’s grown indoors.
Root rot in Viburnum
Viburnum is mainly infected by Armillaria root rot. Affected leaves turn yellow with green veins in the initial stages of infection.
Leaf edges turn brown and wilt when the infection is severe. The roots become brown/black and mushy, giving a rotten appearance.
How do you treat root rot in Viburnum?
There is no treatment for Armillaria root rot. The plant eventually dies due to premature leaf drop, slowed shoot growth, and branch dieback.
You need to dig the affected plants up and dispose of them. Replace the soil if possible.
Bacterial Blight in Viburnum
Bacterial Blight affects the stems and leaves of Viburnum. Angular/Irregular brown spots are seen on the leaves of the infected Viburnum.
The developing leaves get deformed due to heavy infection. Cool, moist conditions favor the spread of this disease to healthy plants.
The bacteria usually infect healthy plants via wounds. The disease also spreads through the gardening tools so clean the tools after using them on infected plants.
Happy Gardening 🙂