Common Rose Diseases

Welcome to the Member Ideas area! This community feature is where our members can post their own ideas. These posts are unedited and not necessarily endorsed by the National Gardening Association.
Posted by @Calsurf73 on
Anyone who grows roses will at one time or another run into problems with disease. Even the most attentive and hard-core rose enthusiast will encounter this problem because, as we all know, we can't control the weather. The majority of rose diseases that we'll discuss here are weather related. Knowing how to identify and understand the causes of these diseases will make your rose growing endeavors easier and more enjoyable, and your roses will be happier in the long run.

Before purchasing a rose for your particular location, it would be wise to research that particular rose and learn how "resistant" it is to various diseases. Disease resistance is a genetic trait that varies from rose to rose. Choosing roses that suit your climate and perform well without constant spraying to cope with outbreaks of disease will save you a lot of time, grief, and disappointment. Few roses will perform well and thrive in every climate across the country. Understanding your weather patterns and selecting your roses according to their "likes and dislikes" is imperative to successful rose growing.

The main diseases most rose gardeners face are:

1.) Black Spot

This is a fungal disease, and as its name implies, it manifests itself as black spots with a feathered edge, surrounded by an irregular yellow "halo" on the surface of rose foliage. Extended periods of dampness and poor air circulation cause the airborne spores of this fungus to develop on leaves that remain wet when there is little air movement. Roses planted too close together with inadequate air circulation are prone to this disease, especially in damp cool climates. Once the foliage develops these spots, the damage is done.

Spraying the plant with a good rose fungicide containing bupirimate or triforine will halt the progression of the disease. Hand pick the infected foliage when it appears and keep the base of the plant free of debris. Careful thinning of a very dense rose will aid in better air circulation. Avoid watering the foliage of your roses when there is little air movement and temperatures are low. Follow the manufacturer's suggestions for follow-up spraying. Some cultivars of roses are highly prone to black spot, so do your homework and try to find a rose suitable for your particular climate that is black spot resistant.

2.) Powdery Mildew

This is another fungal disease, which is white or grayish in appearance and infects the foliage and stems of roses. It is caused by poor air circulation during periods of warm days and cool nights.  The spores of this fungus settle on rose leaves, stems, and buds. Roses that are not getting enough sunlight and/or have been given too much nitrogen are especially prone to this malady. Unlike black spot, powdery mildew develops on dry foliage when temperatures are cool and air circulation around the plant is poor.

2013-02-08/zuzu/209a53

If you notice the beginnings of powdery mildew, you can often hose off the spores with water to halt progression. If the infestation is heavy, spraying the plant with a fungicide containing triforine or bupirimate will help eradicate the disease if done early in the day when there is minimal breeze. Homemade remedies using a combination of baking soda, white vinegar, and insecticidal soaps will neutralize the fungus and make it disappear almost before your eyes when sprayed on the plant. There are various recipes for this treatment, which can be found on the internet and which are environmentally friendly and safe to use.

3.) Rust

This is yet another fungal disease that thrives during periods of high humidity and poor air circulation. Small orange or yellow pustules develop beneath the foliage and burst open, spreading the spores to the rest of the plant, as well as to neighboring roses. A heavily infected plant will also have the spores visible on the upper surfaces of the leaves. The foliage eventually will dry up and fall off the plant, but the spores still will be active.

2013-02-08/zuzu/43afed

Remove all foliage that has collected around the plant to prevent the spread of the disease. Spraying your roses at the first sign of rust will prevent it from spreading. Check at your garden center for a good rose fungicide that will control rust. There are numerous types of rust, but rose rust is specific to roses. Other forms of rust will infect other plants (such as daylilies) without affecting roses, and vice versa. Keep your rose foliage dry and provide good air circulation around the plant. Cleaning up the dead infected foliage that has fallen off the bush is imperative to preventing the spread of this disease because the base of the plant at the soil level can become a breeding ground for the spores.

4.) Rose Mosaic Disease

This is a viral disease, which is ever present in the plant and cannot be eradicated. Symptoms may be visible at any given time, but seem to be more prevalent in the cooler early days of spring. Foliage may take on various forms of "marbleizing" or disfigurement and assorted color variations resembling chlorosis. Plants may appear to be fine throughout the year and then suddenly manifest symptoms of this disease.

2013-02-08/zuzu/e6d528

As there is no cure, removing the symptomatic parts of the plant will improve the appearance of the rose bush. Depending on the particular rose and its vigor, it may or may not produce more infected foliage. This disease is not fatal to the plant, nor is it contagious to other healthy roses which may be in proximity.

5.) Botrytis Blight

This fungal disease, like the others, is caused by poor air circulation and heavy moisture in the air. It generally occurs when spring rains collect and saturate the new blooms. Spots may appear on the petals where the fungus lands and, as the flower gets soaked by the rains (or by overhead watering), the bloom will turn into a brown fuzzy mass and eventually will drop. This disease mainly affects buds and petals, but it occasionally may damage the rose foliage as well. As with all of the previously mentioned fungal diseases, the solution is to keep the buds and blooms on your roses dry. Don't let water get on the buds and blooms when you're watering the plants and keep the area around the plant free of debris.  A Daconil fungicide will aid in the control of this disease.

6.) Rose Rosette Disease

This is a fairly new viral disease, which has had a devastating effect on roses. Sources indicate that the disease is most prevalent on the East Coast and parts of the Midwest. It is highly contagious and there is no cure for it. Transmitted by a mite via winds, and also by grafting onto infected plants, this disease can also spread to other healthy plants by root-to-root contact.  It appears that the disease is most likely to infect roses during hot dry summers.

2013-02-08/zuzu/1f3f90

The symptoms are foliage resembling a "witch's broom," canes with an unnaturally reddish coloration, and stunted or disfigured buds and blooms. Infected plants may live up to 7 years, but they probably will be shorter-lived. At present, the only known method of controlling this disease is the removal of infected plants.  Dig up and destroy the infected plants, as well as a decent amount of the soil they were growing in. It is possible that the early detection and elimination of the infected plants will reduce the spread if you have numerous other roses in your garden.

To summarize, the key elements of growing healthy and disease-free roses are good air circulation, watering practices that keep the foliage dry, and the maintenance of a clean, debris-free space around your plants. Water-stressed roses develop diseases quickly, so keep your roses well watered and fed. Spray when you see the first signs of disease and be vigilant about keeping insect damage at a minimum.  Roses infested with insects will have weak immune systems and will develop diseases more readily.

Other diseases infect roses as well, but this article is an attempt to list only the common maladies that are prevalent across the board. Growing roses successfully isn't a Herculean task if you know what to look out for and if you recognize the signs of trouble as soon as they present themselves.

 
Comments and Discussion
Thread Title Last Reply Replies
Purchasing a new rose bush for beginners, by NurseKaren1 Sep 4, 2023 9:59 AM 0
Common Rose Diseases by valleylynn May 19, 2020 1:00 AM 9
What is this? by CathySueH Mar 15, 2020 5:57 PM 0
What is killing my roses? by Sjcwhittle Aug 9, 2019 4:49 PM 0
What are the most Disease Resistant climbing rose. by Richardis70 Aug 9, 2018 7:53 AM 1

Explore More:

Member Login:

( No account? Join now! )