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Past Articles Library | Plant Diseases & Control | Plant Diseases of Roses 2



Roses are by nature a beautiful plant.  But, while they are very stunning they can be a challenge to keep disease-free.  Below are some of the common plant diseases that one can expect when growing roses.  While there are chemical treatments for these diseases, organic choices are offered as a solution. 

Black Spot

Black spot is one of the most common plant diseases of roses.  It typically starts off as a round spot that is brown to black.  The edges of these spots will have a feathery appearance.  At the same time, the leaves of the rose can begin to turn yellow and fall off prematurely.  The canes of the rose plant will also begin to show signs of black spot.  This will appear as small, purplish spots on the cane.

The organic treatment for this disease is proper maintenance.  This means avoiding getting the leaves wet by only watering the soil.  Second, remove diseased canes and rake up the fallen leaves.  Following these steps will reduce the chances of developing and/or spreading the black spot.

Botrytis Blight

Botrytis blight is a plant disease that really affects the beauty of the rose and that is the flower.  This plant disease will first show up as small, water soaked sores on the petals.  As the plant disease progresses, the botrytis blight will grow into a gray fungus that will cover the flower.  Once the flower is cut, the botrytis blight will travel down into the stem and into the cane.  Girdling will occur once the disease is in the cane.

To prevent this disease, space rose according to the variety you are planting.  As soon as the flower is spent, remove it from the plant and remove any yellowing leaves. 

Anthracnose

This plant disease causes leaf spot.  The first sign of anthracnose is the appearance of a red, brown or purple spot.  As this spot progresses, the center will turn white or gray with a red border, which will house some fruiting bodies.  Once this happens, the center will fall away.  This will leave little holes in the leaves.  While this disease is normally seen in the leaves, it can also be found on the canes.

The prevention process for this disease starts with proper spacing.  This will allow air to flow around the plants and dry them out.  Another step to follow is to only water the soil.  Finally, following good garden hygiene is a must.  Make sure to remove any diseased canes and/or leaves, rake up any fallen leaves, and dispose of the plant material in the trash.

Rust

Rust will appear in the spring and summer.  The first signs of this plant disease start at the lower part of the plant, which includes the leaves and canes.  In this area, rust will create a mass of powdery spores which are orange.  These spores will turn black in the fall and spread to other parts of the plant. 

If you find this on your roses, your only choice is to pull up the plant.  To prevent it from spreading farther, make sure to place the plant in a plastic bag and tie it off.

Rose Rosette

The rose rosette is an easy one to diagnose.  The leaves of the rose will be distorted and bright red.  The canes will be extremely thorny and wildly branched.

The only solution for this plant disease is two-fold.  Dig up the roses and throw them away.  Next, remove any multiflora roses within a 100 foot radius of your rose bed.

Powdery Mildew

This common plant disease starts out as spots.  As the disease progresses, the spots will show a white fungal growth that will end up covering the leaves, stem, and flower parts. 

If you find that you have this problem, do not panic.  It is organically treatable.  Check out this blog to find out how to treat for powdery mildew.

Downy Mildew

If you had a wet spring, chances are you are going to develop downy mildew on your roses.  This disease appears as purplish brown spot on the leaves.  These leaves will then turn yellow in the fall and fall off.  The downy mildew can also appear on the twigs. 

The only organic solution to this problem is to control the moisture in the spring.  While you cannot control Mother Nature, you can manage your own watering system by only watering the ground.

Crown Gall

When a rose has crown gall, the stems will have small white galls.  These galls can grow to be six inches in diameter and can be found on the roots. 

To prevent this disease, do not plant infected plants.  How can you not do this?  Well, the answer is simple.  Make sure to inspect your plant material completely before planting.  If you find that you have planted a diseased plant, dig it up and throw it away.

Cankers

This plant disease starts out as reddish-brown spots on canes.  As the disease progresses, these spots will turn light to dark brown with little black spots.  Once this happens, the canker will travel around the cane and girdle it, which will kill the cane. 

The best solution to this rose problem is to dig up the plant material and throw it away.

Viruses

Viruses can come in many different forms, which include rose or yellow mosaic, mottle, ring pattern or streak virus.  A common thing to look for in this situation is the yellowing of the veins in the leaves.  If you find a yellowing, the only thing you can do is to remove the plant.  To prevent it from happening, only plant disease free plants and control any insect or mite problem you may have.    

As you have read about these rose diseases, you may have noticed a few common solutions.  One is proper spacing of the rose.  This will allow air to travel around the plant and dry it out.  In doing so, you reduce the chances of developing a fungus problem.  Second, proper watering can go a long way in disease prevention.  Rose plants do not like wet leaves while rose diseases do.  Third, inspecting your plant material before purchasing can save a lot of heartache when it comes to growing roses.  Fourth, garden cleanliness is very important.  This means removing spent flowers, discolored leaves, dead and/or dying canes, and diseased plants.  But the key to this latter approach is getting to know your rose plant and knowing the difference between the yellowing of the leaves as the season changes compared to a disease problem.  Finally, always make sure that your equipment is clean and sterilized when dealing with roses.  A lot of disease problems are made worse when pruners are not cleaned between cuts and an open cut is an invitation for a plant disease.  To keep your tools clean and sterilized while you are working in the rose bed is easy.  Prior to starting the day, clean the pruners with soap and water, rinse in bleach water and set out in the sun to dry.  Once dry, you are ready to make that first cut.  After that, remember to wipe down the cutting surface in between cuts with bleach or rubbing alcohol.  This simple step will kill any plant disease, which will keep it from leaping from one plant to another.










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Gardening-tip:



Fertilize Container Plants

Because container gardens are usually grown to show off a lot color, the plants in them require more frequent fertilizing.

It's good to feed them every two weeks with a water-soluble complete fertilizer like a 20-20-20 or a hyrdolized fish fertilizer.

Regular feeding will help them fill in faster, and produce more flowers.


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