How to Identify and Treat Common Rose Diseases

By the end of every fall I find myself swearing off roses. But at the beginning of every summer to follow, they suck me back in.

The promise of gorgeous flowers and carpets of petals, and the delectably tedious art of pruning, makes the headaches over diseases that commonly affect these plants tolerable.

A vertical picture of a flowering rose bush with pink blooms and green foliage on a green soft focus background. To the center and bottom of the frame is green and white text.

At least until the end of fall, that is. Then I give up on them again.

But such is the life of the gardener.

Few plants in the garden offer the refined payout that roses do. From their iconic flowers to their euphoric aromas, roses are a mainstay for a reason.

A close up of the bright red blooms of a rose bush, with green stems and unopened buds, on a green soft focus background.

But this comes at the price of requiring lots of attention to detail in terms of plant health and care.

If you grow roses, you’re almost guaranteed to encounter disease.

Seasoned experts and eager amateurs alike are going to encounter black spot, mosaic, and mildew growing on their roses at one point or another.

Let’s take a look at these common and likely problems you’ll discover, and learn how to address them. But first, we’ll go over a few basics on disease prevention.

Here’s an overview of what I’ll cover:

Tips for Preventing Disease

Roses want full sun conditions and lots of airflow. They also thrive on being doted on, so regular pruning and removal of dead tissue will help minimize the risk of disease.

Hey, roses are a lot like us, aren’t they?

A concrete path meandering through a flower garden, between two borders with different plants in bloom.

Try planting disease-resistant cultivars to start with, to reduce the likelihood of infectious encounters.

I have never been a fan of Knock Out® Roses myself, but they are a popular series because they are generally highly resistant to disease.

Chemical Solutions

Always follow the directions on the label of any chemical solution you use in your garden!

Too much or too high of a dosage is just as bad, or sometimes many times worse, than applying too small of a dosage. Always refer to the label when using any chemical.

On the same note, if you find a strange tip on the internet or in conversation with a fellow gardener, do a little research before following through with it.

As much as I’m a fan of old school gardening techniques, I find too much of this is fluffy nonsense.

Keep Those Pruners Clean ‘n’ Sharp

I sharpen my pruners every single morning, and if I’m doing a lot of snipping, I’ll bring the whetstone with me to the jobsite.

A sharp blade makes a clean cut, and clean cuts minimize damage to a plant while simultaneously helping to prevent infections.

A close up of a hand from the left of the frame holding garden pruners and cutting a stem from a rose bush, in bright sunshine, on a soft focus background.

Many rose diseases easily spread to other plants, oftentimes from a gardener’s pruners.

I carry a spray bottle filled with rubbing alcohol and spritz my pruners between every plant I prune, or sometimes between every few cuts on the same plant.

It’s tedious and annoying, but it’s vital to plant health.

Rose Diseases

These are some of the more common rose diseases the home gardener will encounter.

I’ve listed them in ascending order of severity, with the really nasty ones at the end.

Black Spot

One of the most common rose diseases you’ll encounter is black spot.

Caused by the fungus Diplocarpon rosae, black spot will defoliate and weaken your plants, making them more vulnerable to other environmental pressures.

A close up of the leaves of a rose plant suffering from black spot. The green leaves are turning black in the center and at the edges. The background is foliage in soft focus.

Think of black spot as a gateway disease; it is unlikely to kill your roses by itself, but it stresses your plants and makes them more susceptible to other infections.

This fungal issue is often encountered in the spring and fall, when conditions are wet and cool nights prevent moisture from evaporating.

Warm weather over about 80°F/26°C tends to prevent black spot from occurring in the first place, and dry weather inhibits the progress of this disease.

A close up of bright green leaves suffering from black spot, a disease that attacks roses.
Photo by Matt Suwak.

Water splashing on infected leaves is what spreads the fungus, so a lack of precipitation and unnecessary irrigation means minimal spread of infection!

Black spot often begins its damage at the base of the plant and works its way to the top.

Infected leaves will develop a telling bunch of black spots before the plant drops these leaves.

Infected canes will look bruised and take on a black or purple hue, indicating the presence of infection.

The fungus overwinters in infected leaves and canes, so if your plants have it one year, it’s likely to make an appearance again in the future.

How to Handle Black Spot

Black spot can be treated with a few different types of sprays. However, this is a very difficult disease to handle once an infection sets in, so early care is vital.

A close up of foliage suffering from black spot. The green leaves are covered with black patches in the center and at the edges.

A mixture of about a teaspoon of baking soda with a quart of warm water can be sprayed on the plants, or you can use a sulfur-based fungicidal spray.

I started using this product from Southern Ag last fall, and found the results promising. It’s available on Amazon.

Liquid Copper Fungicide

Neem oil can also work, but I tend to avoid it when working with roses to prevent causing harm to beneficial insects.

Rust

A common problem caused by nine different species of fungus, at its most benign, rust is an ugly condition.

But in the worst cases, it will kill the initial host plant and spread to the others.

A close up of the foliage of a rose plant suffering from fungal rust. The green leaves are turning a light brown, rusty color.

It’s relatively easy to spot rust on your roses.

They’ll often drop leaves, and the condition is obvious with its orange, rust-colored marks that appear on leaves and canes. In the winter, infected canes tend to turn black.

Rust overwinters in infected tissue, but it can also find a safe hiding spot on trellises and fences, or just about any place near the host rose where it is offered some protection from the worst of the winter weather.

Luckily, this fungal issue is specific to roses, so it should only pose a potential threat to the other roses in your garden.

Handling Rust

As is the case with many plant diseases, a thorough and attentive watering regimen is key to solving your rust issues.

Remove fallen leaves every autumn and as an early spring cleanup project to help minimize the spread of this fungal disease.

If you’re in the planning stage of your garden design, consider purchasing rust-resistant rose varieties to dramatically minimize your chances of encountering this annoying problem.

If you opt for chemical control, consider using Bayer Advanced Disease Control instead of a combination fungicide and insecticide.

Bayer Advanced Disease Control for Roses

This is a reliable and readily available over-the-counter choice, and you can find it on Amazon.

Powdery Mildew

If you’re growing roses, you’ve probably encountered powdery mildew before. It leaves a telltale… well, powdery mildew on the leaves, a gray coating that screams “yuck!”

It’s commonly spotted in a variety of plants in the garden, and becomes an almost constant annoyance in late summer and early fall.

A close up of a stem and foliage of a plant suffering from powdery mildew, a fungal infection causing white patches on the leaves.

This fungal disease thrives in humid conditions where airflow is minimal or nonexistent. Sounds like every summer day in Philadelphia, if you ask me!

However, it can also thrive in dry conditions, and that’s what makes powdery mildew such a headache. You just never know when it’s gonna strike.

If it’s a minor case of powdery mildew, I tend to let it go unmended, but will pay close attention to infected pants to ensure the disease doesn’t spread.

A close up of leaves showing powdery mildew, a common rose disease, pictured in bright sunlight with flowers and foliage in soft focus in the background.

Oftentimes this is an issue that will take care of itself in minor cases.

A thorough fall cleanup of all shed leaves is a helpful trick to minimize any recurrences.

Handling Powdery Mildew

Either of the fungicides recommended for the previous fungal issues will help to treat powdery mildew. Any product containing Mancozeb will do the trick.

Make sure you’re spraying all parts of the plant, including the tops and bottoms of leaves, on a regular schedule.

Some experts recommend an application every two weeks, but as always, read the label of your purchased chemical for its suggested usage.

Botrytis Blight

I remember watching some tea roses expectantly, eager to see their developing buds blossom into the lovely flowers I’ve come to love (and detest, depending on what time of the year you ask me about it…) then furrowing my brow as the petals turned brown and crispy.

A close up of a rose bloom suffering from the disease botrytis blight, where the petals go brown and dry out, eventually dropping from the plant.

This was my first encounter with botrytis blight, an awful and ugly disease that most often attacks tea roses, ruining their blooms.

Like most fungal issues, this one is caused largely by environmental issues, so a hot and humid summer is the perfect breeding ground for this disease.

Handling Botrytis Blight

While botrytis blight can be controlled temporarily with fungicides, it often adapts a resistance to these sprays and makes them ineffective after prolonged use.

Sunny, dry weather is often enough to keep this condition under control.

A close up of a rose bloom suffering from botrytis blight. The petals are going brown and drying out. The background is soft focus.

An interesting solution to handling botrytis blight rests in your fertilization practices.

Too much nitrogen can create an abundance of new, soft growth that is overly susceptible to this blight.

Limit any midsummer feeding you provide to your roses to help minimize the risk of blight attacking that new growth.

Cankers

This one is an ugly, potentially fatal fungal infection for your roses.

A close up of a green stem showing characteristic dark spots of stem canker, a disease of roses.
Photo by Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org, via CC 3.0

Canker reveals itself by turning the canes black, most notably in locations where the plant was recently pruned.

Always clean your pruners between different plants to prevent this from happening!

A vertical picture showing a close up of a devastating stem canker, a common disease on rose shrubs.
Photo by Florida Division of Plant Industry , Florida Department of Agriculture and Consumer Services, Bugwood.org, via CC 3.0

Interestingly, cankers often cause the most trouble during the colder periods of the year, making them a bit more difficult to notice than other diseases.

I’ve encountered them during early springtime pruning, either by discovering old cankers, or noticing new ones taking hold.

Roses are susceptible to three types of canker:

1. Brown Canker

You’ll find tiny, raised, reddish-purple bumps on the canes, a little less than half the size of a grain of rice. As these little spots begin to mature into their fruiting bodies, they develop a brown or black color.

2. Brand Canker

These have a similar reddish color as the brown variety, also found on the canes, but these cankers quickly develop a brown center. I’ve yet to see a brand canker without that brown central coloration.

3. Stem Canker

Sometimes harder to spot at a glance than the others, stem canker tends to have a yellowish color, but it can also swing towards the red slice of the color wheel. This type of canker shows up on the bark.

Handling Cankers

Using clean, sharp pruners, remove the infected tissue and canes.

I’ve seen people cut two to three inches below the infected tissue, but I go farther than that if it’s a widespread issue, sometimes removing 75% of an infected stem.

Cut into the healthy, green area of the plants, and follow up with a fungicidal treatment to give your roses an added boost against reinfection.

Preventing cankers is surprisingly easy: mulch their roots to prevent the plants from getting too cold in the winter, and make sure you provide adequate amounts of fertilizer.

Crown Gall

As we’ve moved through this list, we’ve talked about rose diseases in order of their severity, so you know crown gall is serious business.

It’s also one of the most easily identifiable of all rose diseases.

A close up vertical picture of a rose stem suffering from crown gall, with a large brown mass growing on the stem.
Photo by Jennifer Olson, Oklahoma State University, Bugwood.org, via CC 3.0

Crown gall is an ugly, weird-looking growth of tissue that looks like a mix between a brain, a praying mantis nest, and a head of cauliflower.

It can be a smaller mass of tissue or a larger one, and can occur almost anywhere on the rose, but it almost always develops near the soil level or crown of the plant.

It is caused by a bacterium (Agrobacterium tumefaciens, for the Latin lovers) that enters wounded tissue.

Though it’s easy to identify once you spot it, most of the time, this disease is not noticed until weeks after the date of infection.

Handling Crown Gall

Well, this one is simultaneously easy and sad: remove the infected plant and destroy it, and do not plant another rose in this location for two years.

A close up of a green branch showing a large growth of crown gall, a disease of rose bushes and other plants, on a soft focus background.
Photo by Jennifer Olson, Oklahoma State University, Bugwood.org, via CC 3.0

The goal here is to get rid of any residual bacteria in the soil, and any of the original rose’s infected roots, before replanting in that area.

Treatments are available to slow the growth of a crown gall and to minimize its damage, but these efforts will not kill this infection.

Treatment only slows the progress of the disease and is not recommended.

Rose Rosette

In my opinion, this is the saddest-looking disease a plant could possibly develop.

It’s as if the physical traits of rose rosette disease were meant to twist and warp a rose just enough that it’s still beautiful, but in a very ugly way.

A vertical picture of a plant suffering from rose rosette disease, with dark red stems and foliage and lots of tiny new thorns, on a green soft focus background.

You’ll notice this disease, which is spread by a virus-carrying mite, when you see the telltale bizarrely red growth of the plant.

Other early symptoms include deformed and brittle leaves with yellow and red pigmentation.

As the disease progresses, the rose develops smaller leaves and vibrant red shoots.

You’ll also notice a dramatic increase in the number of thorns on the stems of your roses.

A close up of the stem of a plant suffering from rose rosette disease showing the large number of tiny new thorns, set on a stone background.

They will come to look like something more akin to a wild bramble than your favorite rose.

This disease spreads throughout the summer as the mites travel on the wind and infect new plants, laying eggs over a 30-day period.

Handling Rose Rosette

Rose rosette tends to infect wild roses far more readily than cultivated ones, but anything in the genus Rosa is susceptible.

It’s recommended that you plant your roses as far away from wild roses as you can, to avoid transmission.

A close up of a section of rose bush afflicted by the devastating rose rosette disease, with red foliage and a large number of new thorns on the stems, set on a white surface.
Photo by Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org via CC 3.0

Prune your roses hard each year (I prune mine on the first decent days of early spring), cutting back as much as 70% of last year’s growth.

This helps remove any overwintering mites and potentially infected tissue.

You can also apply insecticidal soap, but be warned that these chemicals kill almost any insect they come into contact with, including natural predators that feed on the mites.

If you’ve got a plant that is infected with rose rosette disease, you only have one real option for control: destroy the plant and burn it, or place it into a plastic bag and dump it with the garbage.

I’d recommend bagging the plant before removing it, to prevent spreading the mites as you carry it around the yard.

You can still plant a new rose in the same location, since the disease is transmitted via mites that do not overwinter in the soil.

Get Ready for Healthy Roses!

Now that we’ve gone over the diseases you’re likely to encounter, you’ll be ready to hit the ground pruning this season and enjoy a fabulous display of healthy blooms.

A garden scene with red and pink blooms in the foreground, and an arched pergola covered in climbing roses, with trees in soft focus in the background.

Still have questions? Please drop us a line in the comments below, or share your own tips and tricks for rose disease management.

Check out our rose pruning guide to brush up on that skill, and if you choose to apply any type of chemicals to your roses, read our pesticide application guide.

And to read more about diseases and pests that can invade your garden, try these guides next:


Don’t forget to Pin It!

A collage of photos showing different photos of diseased rose plants.

Photos by Matt Suwak © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: Shutterstock. With additional writing and editing by Clare Groom and Allison Sidhu.

About Matt Suwak

Matt Suwak was reared by the bear and the bobcat and the coyote of rural Pennsylvania. This upbringing keeps him permanently affixed to the outdoors where most of his personal time is invested in gardening, bird watching, and hiking. He presently resides in Philadelphia and works under the sun as a landscaper and gardener, and by moonlight as a writer. An incessant questioning of “Why?” affords him countless opportunities to ponder the (in)significance of the great and the small. He considers folksy adages priceless treasures and is fueled almost entirely by beer and hot sauce.

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Chris Meinhardt
Chris Meinhardt (@guest_6074)
1 month ago

Great guide! I am wondering if you can help me determine if my knockout roses are being impacted by one of the diseases you mentioned. I’m having a difficult time trying to find a disease picture online that matches.

Allison Sidhu
Allison Sidhu (@allison-schultz)
Admin
Noble Member
Reply to  Chris Meinhardt
1 month ago

Sure, are you able to upload a photo?

Cindy
Cindy (@guest_7193)
14 days ago

Why does my rose bush look wet and sappy on the leaves? Is it from the wasps that are always around it?

Sandi Stephens
Sandi Stephens (@guest_7228)
13 days ago

I have searched the internet for weeks about this problem with my roses and have had no luck identifying this problem. As you can see from the photos, the rose looks dead on one side. A couple of weeks ago this plant was perfectly healthy looking and full of blooms. Suddenly the limbs and leaves start dying and this typically spreads to the whole plant. It seems to be contagious to nearby roses. The photo of the monster tomato plant I’ve included is about 10 feet from this rose and is obviously not affected by whatever is affecting the roses.… Read more »

Angela
Angela (@guest_7745)
2 days ago

Enjoying your guide but cant seem to figure out what’s going on with my always healthy knockout roses this year. Any idea what this could be? Thanks, Angela

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Chiara
Chiara (@guest_7763)
1 day ago

Hi there, I’m trying to identify what’s going on with my roses. They seem fine from afar, leaves and new growth look nice enough, a bit chewed on maybe but that’s life. The stems on the other hand look all damaged, some are woody and cracked and others with brown purplish spots.

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Chiara
Chiara (@guest_7801)
Reply to  Matt Suwak
9 hours ago

Thank you for the fast response! Yes, rainy April plus my incorrect watering (live and learn).About the pruning, should I do it the sooner the better, or wait, I don’t know, after the blooming? And, most of all, what if the spots go all the way down? Thanks