How to Identify and Treat Common Viburnum Diseases

Viburnum is a genus of over 150 species of deciduous and evergreen perennials that feature showy flowers and attractive foliage, many of which are native to North America.

Most species are woody shrubs, though some have a spreading growth habit, and others can be pruned into a tree-like form.

These versatile, low-maintenance plants are easy to grow and – depending on the species and growing zone – will thrive in shady locations or full sun.

A close up vertical image of a flowering viburnum shrub growing in the garden pictured on a soft focus background. To the center and bottom of the frame is green and white printed text.

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In our guide to growing viburnum, we cover how to cultivate these plants in your landscape.

In this article, we provide an overview of the major diseases that may affect viburnum, most of which are treatable, and we explain how to control them.

Here’s what we’ll cover:

Fortunately, viburnum is generally resistant to most diseases. Infected plants typically have been weakened by improper care or are in poor health otherwise.

Therefore, you should be able to prevent disease by ensuring that their needs are met.

A horizontal image of a viburnum shrub growing in the autumn garden with other perennials and trees in soft focus in the background.

Growing these shrubs in full sun will help to prevent many of these diseases, which typically occur in damp, moist conditions.

If the plant has grown very densely, the interior may retain moisture. Pruning the branches in the center of the plant can help to increase airflow and prevent a build up of humidity.

Also remove any plant material that falls to the ground, since it may harbor disease-causing organisms.

If, in spite of your best efforts, your shrub appears to have come down with symptoms of a disease, it’s likely to be caused by one of the following six conditions:

1. Algal Leaf Spot

As its name indicates, this disease causes an infection that shows symptoms on the leaves. The spots start out small and pale green before becoming reddish or light brown. They often have feathered edges and look like they are slightly raised.

Cool and moist conditions favor the development of algal leaf spot. Wind and splashing rain will spread this type of algae to nearby foliage.

The organism that causes it, a type of algae known as Cephaleuros virescens, overwinters in the leaf spots, ready to strike again in springtime.

You can control algal leaf spot with copper fungicide, such as this one from Bonide that’s available from Arbico Organics.

A close up vertical image of a spray bottle of Bonide Copper Fungicide isolated on a white background.

Bonide Liquid Copper Fungicide

Treat your viburnums when you first see the symptoms, then repeat every 10 to 14 days until the disease is under control.

2. Armillaria Root Rot

Unfortunately, species of Armillaria (the honey mushroom) are found in soils throughout the world, and may cause fatal infections on a variety of trees and shrubs, including viburnum.

You may have no idea that your shrub is infected until it suddenly dies. Symptoms include yellowing of the leaves and stunted growth.

You can observe signs of the presence of this fungus as a white mat if you peel back the bark near the bottom of the shrub. Sometimes there will be stringy black growths on the roots or the soil surrounding your plant that are known as rhizomorphs or shoestrings.

There is no cure for this disease, and if you discover that your viburnum has a severe infection, you should immediately dig it up and destroy it in the trash, not on your compost pile.

Try and remove as many roots as you can and destroy those, too. This will help to prevent the fungus from remaining in the soil and infecting other plants.

In addition, you should remove the soil from around the root zone and dispose of it.

You will not be able to grow viburnum in the same area once the soil has become infected.

However, healthy plants are less likely to contract this disease, so make sure the soil drains well, fertilize properly, and provide additional water during periods of drought.

3. Botryosphaeria Canker

This fungal infection is serious, but fortunately it only afflicts shrubs that are already in poor health.

Your viburnum will be the most susceptible if it’s drought stressed, so be sure to provide additional irrigation during dry spells.

Areas of the shrub that have been pruned or that have damaged bark are also vulnerable to invasion by this fungus. Healthy plants will generally ward off such infections, but they can spread in unhealthy ones.

The first indication of this disease is leaves that wilt and die.

Next, the branches die. They will be covered with black or dark brown pimple-like fruiting fungal structures. If you look under the bark, the wood will be dark brown.

The afflicted areas will eventually become sunken, causing cankers to form. The cankers start out small, but they can grow together to form larger ones that can girdle the affected trunk or branch. This prevents water from moving throughout the plant.

Areas with cankers may fail to grow leaves the next spring.

Prune back the branches that are infected. Cut them all the way back to the green healthy wood, and sterilize your pruning shears between cuts.

If you have to prune an entire branch, cut just outside of the branch collar and do not make the cut flush with the trunk.

Be sure to destroy the material you pruned, since it contains fungal spores that could spread.

If you have mulched your shrub, it will be more resistant to mechanical injury from lawn mowers and weed wackers. Apply two to four inches of leaf mold, bark, or pine needles. Do not pile the mulch up against the trunk.

4. Downy Mildew

This is a disease that doesn’t kill its host, but it can be debilitating on viburnum.

Downy mildew is caused by Plasmopara viburni, and it is typically a problem when the weather is wet in the spring and moisture builds up on the leaves.

Symptoms include angular spots between the leaf veins that grow larger and cause the leaves to redden and turn brown before they shrivel up and die. The underside of the leaves will be covered in white fungal growth.

You can take measures to prevent this disease by raking up and destroying any infected leaves. It is particularly important to do this when the leaves fall to the ground in the autumn. Any diseased leaves that remain on the ground can cause infections when the rain splashes the spores to the new growth.

Do your best to keep the leaves dry. For example, avoid using overhead irrigation, and water only at the base of the shrub.

Prune any overhanging tree limbs or adjacent shrubs that might be growing into your plant, causing a damp, humid environment.

If you observe this disease, apply a copper fungicide as soon as possible. However, be sure to avoid those containing sulfur, since they can be toxic to viburnum.

5. Fungal Leaf Spots

While these diseases can be unsightly, they generally do not cause serious problems on viburnums.

A number of types of fungi can produce leaf spots on viburnum, including species of Cercospora, Phoma, and Phyllosticta.

These infections occur first on older leaves. Moist conditions in the summer typically favor these diseases.

The leaf spots generally start out being angular or irregularly shaped, and the tissue in the lesions is sunken and dry.

As they enlarge, the spots can merge into larger lesions and turn grayish brown or reddish in color.

In addition, species of Colletotrichum can cause anthracnose, which leads to leaf spotting as well.

Anthracnose first shows up as reddish-brown spots on the foliage. If left unchecked, dark, sunken areas develop as the tissue dies. In the case of a severe infection, it may spread to the stems.

You can often prevent these infections by keeping the leaves dry, by avoiding overhead irrigation and improving air circulation. Pruning any overhanging trees around the diseased plants will reduce the levels of humidity and help the foliage to dry as well.

If the infection is minor, remove the spotted leaves. Rake up any infected leaves and destroy them. These steps will help to minimize the chances that your shrub will be reinfected during the next season.

In the case of severe infections, you can treat the plants with copper fungicide when you first see symptoms and repeat at 10- to 14-day intervals as needed.

6. Powdery Mildew

Powdery mildew is caused by Erysiphe sparsa fungi, which will appear as white, powdery growth on the top of the leaves of young plants, and sometimes the undersides as well. It typically causes little damage. However, severe infections can cause the newly developing leaves to become deformed.

Humidity favors the development of this disease, and it is typically a problem when the days are warm and the nights are cool. Rain inhibits its development.

Viburnums growing in the shade are more likely to become infected.

You can prevent powdery mildew by pruning the branches in the interior of the plant, to improve airflow. Also be careful when you are watering, and just water the ground and not the foliage.

If you observe this infection, quickly remove the affected leaves as well as any debris beneath the plant.

Consult our guide for more information about treating powdery mildew.

If powdery mildew is a common problem in your area, you can plant cultivars that have some resistance, such as V. burkwoodii ‘Mohawk’ or V. carlecephalum ‘Cayuga.’

A close up square image of the light pink flowers of Viburnum x carlcephalum 'Cayuga' growing in the garden pictured on a dark background.

V. carlecephalum ‘Cayuga’

You can find V. carlecephalum ‘Cayuga’ plants in #3 containers available from Nature Hills Nursery.

Keep Your Viburnums Healthy

Viburnums generally do not contract diseases and are usually fuss-free, healthy plants.

However, when the shrubs face adverse growing conditions, such as drought stress or excessive amounts of moisture, fungal pathogens have an opportunity to take hold.

A horizontal image of a large flowering viburnum shrub growing in the garden with trees in soft focus in the background.

Have your viburnums come down with a disease? If so, let us know how it worked out for you in the comments section below.

And for more information on growing shrubs in your garden, check out these guides next:

Photo of author
One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the childhood discovery that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.
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Drew A
Drew A (@guest_16787)
1 year ago

What would cause this problems on my sweet viburnums in south Alabama?

Drew A
Drew A (@guest_16788)
1 year ago

Here the pic

Kristine Lofgren
Kristine Lofgren(@kristinelofgren)
Gardening Writer
Reply to  Drew A
1 year ago

Hi Drew, can you try uploading the photos once again? It doesn’t look like they came through.

D Shelby
D Shelby (@guest_17710)
1 year ago

Hello, I’m wondering if you can help my diagnosis this. We’ve had a very warm wet Spring. I pruned it hard and found this.

D Shelby
D Shelby (@guest_17711)
1 year ago

Posting pic

D Shelby
D Shelby (@guest_17712)
Reply to  D Shelby
1 year ago

Looks like the photo attachment function isn’t working. Is there any other way I can get the photo to you?

D Shelby
D Shelby (@guest_17713)
1 year ago

Another try

Kristine Lofgren
Kristine Lofgren(@kristinelofgren)
Gardening Writer
Reply to  D Shelby
1 year ago

I’m sorry you’re having trouble attaching a photo. Could you describe the issue? Or perhaps head to our Facebook page and send the image to us there?

Amy Seroussi
Amy Seroussi (@guest_18211)
1 year ago

Can I send you a pic of some viburnums that were planted last fall? They look anemic now. I think they have wet feet.

Clare Groom
Clare Groom(@clareg)
Reply to  Amy Seroussi
1 year ago

Hi Amy, yes, please do upload a pictures so we can take a look. To do so, click the paperclip icon on the bottom right of the comments box, this will prompt you to upload your image.

Judy (@guest_19181)
1 year ago

This Viburnum was replaced last July for doing the same as it is now. Leaves drooping , turning lighter green to yellow with brown spots on the leaves. What’s interesting is there are two viburnums next to it that have never been affected. What do you think it is?

Clare Groom
Clare Groom(@clareg)
Reply to  Judy
1 year ago

Hi Judy, apologies for the picture not attaching properly to your comment, I’ve uploaded here. Someone will be along soon to help!

Sickly viburnum growing in the garden.
Kristine Lofgren
Kristine Lofgren(@kristinelofgren)
Gardening Writer
Reply to  Judy
1 year ago

Hi Judy, it looks like your plant has some sort of fungal leaf spot disease. While it’s hard to say which specific disease is harming your plant (Cercospora spp., Phoma spp., and Phyllosticta spp. are the most common), it’s not surprising that it would infect your new plant since most of these can either live in the soil or on plant matter like small roots left behind when you removed the last bush. A newly planted shrub is more likely to contract a disease or to show symptoms than established plants. Your best bet is to use a broad-spectrum fungicide… Read more »

joe (@guest_19546)
1 year ago

Hi I have some viburnums shasta . I planted full grown bushes in June from a good nursery. I live in NH … They were thriving and produced nice berries. now turning yellow and my customer is freaking out. here are some attached pics … hope you might be able to help

Clare Groom
Clare Groom(@clareg)
Reply to  joe
1 year ago

Hi Joe, here are your pictures, they didn’t seem to attach properly the first time!

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Screen Shot 2022-09-03 at 9.29.33 AM.png
Mark Maloney
Mark Maloney (@guest_19772)
1 year ago

For the last couple of years, my sweet viburnum has been completely infested with aphids, white flies, and ants. I have tried everything. I thought I had it under control but a whole section of the line had black, sooty leaves and now the stems and branches are turning blackish, too. The leaves are falling off … it’s depressing. Can you help me with this?

Kristine Lofgren
Kristine Lofgren(@kristinelofgren)
Gardening Writer
Reply to  Mark Maloney
1 year ago

Hi Mark, I’m sorry you’re having such a hard time with these pests. As they eat, the aphids and white flies leave behind a sticky substance called honeydew. This honeydew attracts ants and it also attracts sooty mold. It sounds like that’s what you’re dealing with now. Sooty mold doesn’t hurt the plant itself, but it does restrict its ability to photosynthesize. Combined with the pest feeding, this causes leaf drop. You don’t really need to address the sooty mold. If you get a handle on the aphids and white flies, the mold will go away on its own (or… Read more »

Anna (@guest_24767)
1 year ago

Hi, some of my viburnum have just one branch dies, the rest of the plant looks good. I’d be most grateful for any advice. I’ll attach photos. Thank you, anna

Clare Groom
Clare Groom(@clareg)
Reply to  Anna
1 year ago

Hi Anna, I’ve managed to retrieve the photo you uploaded and attached it here. Someone will be along shortly to help you out.

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Kristine Lofgren
Kristine Lofgren(@kristinelofgren)
Gardening Writer
Reply to  Anna
11 months ago

Hi Anna, sorry to hear about your plant. Whenever just part of the plant dies, rather than the whole thing, my first thought would be Botryosphaeria dieback. This fungal disease can kill off branches, sections, or an entire plant if not caught. It’s more common on plants that suffer from drought stress or are damaged by pests, pruning, or edgers. You can’t treat it with chemicals, but if you prune away the dead area back to living tissue, new growth will likely be healthy. Just keep your plant well watered and avoid damaging it, if possible. Speaking of, look closely… Read more »