How to Identify and Treat Hydrangea Diseases

There are few things more beautiful than lush hydrangea bushes. Unfortunately, their beauty can be sullied by a number of fungal and viral diseases (and two bacterial diseases).

However, there are steps you can take to keep your beauteous shrubs from falling victim to one of these diseases.

Close up of hydrangea leaves showing brown spots caused by disease.

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We will introduce you to the major hydrangea diseases, so you know what to look for and how to prevent and treat them.

Fungal Diseases

Botrytis Blight (Botrytis cinerea)

This fungus can severely affect the flower buds and even kill them before they open. In addition, infected flower parts can fall on the leaves and infect them.

The first symptoms are water-soaked spots on the flowers. However, these grow into reddish brown lesions.

Blue hydrangeas with red lesions on leaves indicating The reddish lesions on the leaves indicating a Botrytis Blight infection.
The reddish lesions on the leaves are a sure sign of Botrytis Blight.

Botrytis is more likely to be a problem under cool and damp conditions, such as several days of cloudy, humid, and rainy weather.

You can take steps to try and prevent this infection. Keep the humidity low. Don’t water late in the day, and only water at the roots, so you don’t get the flowers and leaves wet.

If you can, keep good airflow around your plants. Space them properly, and prune branches that are closely spaced. Treat your pruning shears with bleach as you prune, so you don’t accidentally spread any disease.

Also remove dead or damaged flowers and leaves to prevent the fungus from gaining egress into the plant. Clean up debris around the plant, so that Botrytis can’t live on the dead tissue.

If you have a persistent problem, you may need to use fungicides. Options include iprodione, or thiophanate-methyl.

Leaf Spots (Cercospora species and Phyllosticta hydrangea)

Cercospora manifests as circular purple or brown spots on the bottom of the plant. As the lesions get larger, the leaves can turn yellow and fall off the plant.

Close up of hydrangea leaves showing a leaf spot fungal infection.

Watering without getting the leaves wet will help to prevent these diseases. If your hydrangeas do get infected, you have several options, including compost tea, hydrogen peroxide, garlic oil, or liquid kelp.

You can also apply the fungicides chlorothalonil or thiophanate-methyl.

Anthracnose (Colletotrichum gloeosporioides)

Plants that have been heavily fertilized are more likely to contract this common fungal pathogen.

A hydrangea leaf showing heavy signs of anthracnose infection.

Continued rainy weather or heavy fog produces the conditions that favor infection.

The fungus produces large brown spots on the leaves or flowers that will become more lightly colored in the centers. One distinctive symptom is that spots by the veins develop at an angle.

You can also treat this disease with liquid kelp, garlic oil, hydrogen peroxide, or compost tea.

Read more about identifying and treating anthracnose on hydrangea here.

Powdery Mildew (Erysiphe polygoni)

Powdery mildew manifests as a white powdery substance on the surface of the leaves. You can see white, cottony growth on the bottom of the leaves.

A severe case of powdery mildew. Photo via Alamy.

Left unchecked, the fungus can infect the newly developing buds and stunt their growth.

Powdery mildew is most likely to be a problem on hydrangeas when the days are warm and the nights cool.

You can prevent the disease by reducing humidity and increasing air circulation.

One way to control this disease is to apply a fungicide as soon as you discover it. Another option is to use neem.

Rust (Pucciniastrum hydrangea)

Like other rusts, hydrangea rust needs two hosts to survive and does not kill either of them. This rust only infects the smooth hydrangea, H. arborescens, and hemlock as its alternate host.

The first symptoms are orange pustules on the bottoms of the hydrangea leaves and yellow spots on top.

This disease is difficult to control, but you can manage it by cleaning up infected leaves and debris that has fallen to the ground around both hosts. Thin inside the hydrangea making sure to disinfect your pruning shears.

If you know that rust is likely to be a problem, you can grow the cultivar ‘Frosty,’ which is resistant to this disease.

Bacterial Diseases

Bacterial Wilt (Ralstonia solanacearum)

This important bacterial disease first manifests as blight in the leaves and flower clusters. However, more severe infestations can cause both wilting and root rot.

Bacterial wilt occurs mainly in hot weather and heavy rains. There are no chemical options to control this disease.

Bacterial Leaf Spot (Xanthomonas campestris)

The bacteria that cause this disease can enter the plant through natural openings like stomata or through wounds.

Top down view of of an oak leaf hydrangea leaf showing splotches of bacterial leaf spot.
Bacterial Leaf Spot (Xanthomonas campestris) on oak leaf hydrangea. Photo (cropped) by Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org via via CC 3.0.

The first symptoms are water-soaked spots. The spots darken and become angular in shape. These spots become larger lesions and can kill the leaves.

If you have a susceptible plant, you can protect it with copper hydroxide (Kocide).

Viral Diseases

Fifteen different viruses afflict hydrangeas! Hydrangea macrophylla is the most susceptible.

Transmission can occur by knives, leaf contact, and insects like aphids. In some cases, plant parasitic nematodes can transmit the viruses.

Prevention is the key in these cases. Quickly remove infected plants and their parts. Sterilize your pruning shears before cutting the plants, and plant clean stock in soilless media to avoid the viruses that are transmitted by nematodes in the soil.

These three are the most common viral infections that you are likely to encounter:

Hydrangea Ringspot Virus

If your hydrangea has brown spots or rings on its leaves, there is a good chance that it is infected with hydrangea ringspot virus. Then the leaves of the plant will start to be distorted and rolled, and the growth of the plant will be stunted.

Close up of brown spots and rings on hyrdrangea leaf indicitive of Hydrangea Ringspot Virus.

Aphids do not spread this disease. However, it spreads mechanically, so tools can transmit this virus. Sanitizing your pruning tools will help to prevent the spread of this disease.

Unfortunately, if your hydrangea contracts this disease, you will have to purge it. Varieties that are tolerant to this virus are available.

Hydrangea Mosaic Virus

Hydrangeas infected with this virus will have a pattern of yellow mosaics on their leaves.

Top down close up of yellow rings on a hydrangea leaf indictive of Hydrangea Mosaic Virus.

This is another virus that is not transmitted by aphids. However, once again, you can spread the virus with your tools. So be sure and disinfect your pruning shears to avoid inadvertently spreading this virus.

Tomato Ringspot Virus

This virus causes the leaves to turn yellow and become distorted, and the growth of the plant will be stunted.

Nematodes, not pruning tools, spread this virus.

If you are growing your hydrangeas in containers, you can avoid tomato ringspot virus by using a soil mix that is free of nematodes.

Such Beautiful Plants and So Many Diseases

There are a number of different organisms that can infect hydrangea plants and sully their beauty.

However, you can take steps to keep your plants from becoming infected:

  • Prune your plants, so that the insides are open and will not accumulate moisture. (And disinfect your pruning shears or flower-cutting knives whenever you use them!)
  • Pick up dead flowers and leaves, since they can harbor fungi.
  • Water your plants at the bottom, so the tops will not get wet.
  • Control insects, since they spread many of these diseases.

Have you encountered a disease on your hydrangea? If so, let us know in the comments.

And if you want to know more about growing hydrangea bushes, then check out some of our other guides such as:

© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: Shutterstock.

About Helga George, PhD

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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Amanda James
Amanda James (@guest_5215)
2 years ago

I have a problem fungus that I can’t seem to identify or treat properly. These hydrangeas are heirloom, 7th generation plants, and they’re dying quickly. Help!!

Amanda James
Amanda James (@guest_5217)
Reply to  Helga George, PhD
2 years ago

It’s not responding to any of the fungicides I try

amanda james
amanda james (@guest_5219)
Reply to  Helga George, PhD
2 years ago

This is what it looks like

vivian gerard
vivian gerard (@guest_11515)
Reply to  amanda james
7 months ago

what would i use for a systemic for hydrangas in bc thankyou

amanda james
amanda james (@guest_5220)
Reply to  Helga George, PhD
2 years ago

I can’t seem to get them to upload, or delete the comments that uploaded without the pics

Mike Quinn
Mike Quinn (@mike20)
Active Member
Reply to  Helga George, PhD
2 years ago

 Helga George, PhD

Here are Amanda’s photos of her hydrangeas:

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amanda james
amanda james (@guest_5230)
Reply to  Helga George, PhD
2 years ago

I’ve thinned the plants and actually have been using the neem oil on it for a few weeks and it hasn’t helped. Is there anything a bit stronger that may work?

Amanda James
Amanda James (@guest_5236)
Reply to  Helga George, PhD
2 years ago

I will try that. Thanks so much! Sorry for the technical issues 🙂

Japjeet Aulakh Maan
Japjeet Aulakh Maan (@guest_7734)
Reply to  Helga George, PhD
1 year ago

My hydrangea leaves are getting folded and looks different in colour

Christine French
Christine French (@guest_5383)
1 year ago

I purchased a hydrangea tree about 3 months ago. I potted it with the idea of bringing it into my home this winter (always bring my tree hibiscus in). However, the hydrangea is not doing well. Not sure if I did not give it enough water, but there are spots on the leaves. Will I make a mistake to bring it into my home? We live in Indiana.

Tina
Tina (@guest_5405)
1 year ago

Have browning leaves and flowers turn brown also

Andy Tanguay
Andy Tanguay (@guest_5510)
1 year ago

Can you tell me what is killing my hydrangeas? They have not flowered in a long time & have been planted in front yard for 5+ yrs

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Andy Tanguay
Andy Tanguay (@guest_5513)
Reply to  Helga George, PhD
1 year ago

thank you

Harriet
Harriet (@guest_5733)
1 year ago

Please help, Helga! We have had an ongoing problem with dieback on certain plants in our yard for years. I’m not sure it is the same disease in all the plants, but it acts the same. The branches wilt and then die back, usually in the fall, and the brown leaves cling after the other leaves drop. It affects both our oakleaf and mophead hydrangeas, our pawpaws, dogwood, and azaleas. We have heavy shade and heavy soil in our yard, and hot summers here in Columbia, SC. Our yard stays quite dry due to a combination of the heat, a… Read more »

Harriet
Harriet (@guest_5756)
Reply to  Helga George, PhD
1 year ago

A million thanks, Helga! I was afraid that might be what has been going on. I will just plan on replacing the plants with other selections as it becomes necessary. ????????????

Dan Green
Dan Green (@guest_5816)
1 year ago

I planted my first hydrangea a couple of months ago and I’m afraid it’s not doing well at the moment. It is still small and today I went in the backyard where it is and noticed spots on many of the leaves as well as several leaves having large sections missing. I fertilized the plant a month or so ago with Miracle Gro and it gets watered weekly by my sprinklers. I don’t want to lose this plant that I hope to be a beautiful addition to my back yard. Any guidance you could give me would be much appreciated!!

Dan Green
Dan Green (@guest_5817)
Reply to  Dan Green
1 year ago

Here are the photos I attempted to attach to the original message. Thank you!!

A4380CA9-E6AD-4C06-BF61-79236E7B372A.jpeg
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Dan Green
Dan Green (@guest_5826)
Reply to  Dan Green
1 year ago

Here are a couple of photos.

6381C228-4B81-475B-B38F-00D6D27CB0C3.jpeg
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Gary
Gary (@guest_6107)
1 year ago

Hello, thanks for the very informative article. I have around one hundred hydrangeas throughout my yard. I’m used to seeing and treating many of the listed diseases or just letting the hydrangeas be hydrangeas in the fall with the brown spot. This is the first spring I’ve really noticed a white spotting of the leaves. It’s only on the macrophyllas I notice it. Panicle, arborscens, querciflora and anamola aren’t showing the spotting and mild leaf distortion. It’s been cool here and just a storm the past couple weeks don’t seem to be conducive to most diseases I deal with during… Read more »

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Ryan
Ryan (@guest_6124)
1 year ago

Hi Helga,
Every year I have problems with oak leaf hydrangeas. I can never find info online of anyone having the problem. I get them with the leaves curled and crunchy, some varieties more then others. I take off the bad leaves, but throughout the growing season they keep getting ugly leaves. I’ve had another grower say “they just don’t like being potted” but I’m not sure if it’s another reason.

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Ryan McMullin
Ryan McMullin (@guest_6236)
Reply to  Helga George, PhD
1 year ago

I’m sure I can soon. I just received these hydrangeas the day I sent them to you. I’ve gotten them from three suppliers in the past. All normally come with the leaves like that. I’ve only had one variety in the past that has not. I normally take off any bad foliage and pick up any in the pot but eventually it always comes back. I planted one in my personal garden and it ended up being fine. It’s always the ones I have in pots. As the season goes on I’ll try to get more pictures. But typically it… Read more »

Ryan McMullin
Ryan McMullin (@guest_6237)
Reply to  Ryan McMullin
1 year ago

I just noticed another person describing the same problem below.
I just got fresh water hooked up to my main water this season because I hate having a constant fertilizer for my plants. I’m hoping it has just been over fertilized.

Ruth McHugh
Ruth McHugh (@guest_6140)
1 year ago

Hello, I’m having serious problems with two plants I bought last summer for large containers. They survived the winter with no obvious problems but over the last few weeks have started going brown at the leaf edge and the new buds. Please help

5D743A96-9DDD-4E91-AAB1-FA50E1579B31.jpeg
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nancy
nancy (@guest_6171)
1 year ago

I received a beautiful hydrangea plant for Easter and the blue blooms were beautiful. Now I noticed the blooms are starting to die from the inside out. I live in Michigan and have the plant in my house. What do you think the problem is?