Dealing with Rose Diseases

How to Control Black Spot Fungus Disease on Roses….

Roses have a reputation for getting all kinds of diseases. While modern roses are a lot less prone to problems than the tea roses favored not so long ago, there will inevitably be seasonal rose  problems to deal with.

Most rose diseases are caused by damp or humid weather.  While you can’t do anything to control the weather, you can give your rose bushes good air circulation, so they are able to dry off as best they can.

This will help avoid rose diseases to some degree, but not entirely. You will also need to keep tabs on your rose bushes so that you can remedy any bad situation before it gets out of hand.

Be sure to accurately identify the problem before reaching for a spray and start with the least toxic solution.


To make sure that your prized roses remain in the best of health, simply follow these tips.

Black Spots on Leaves

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Black spot is a fungus that is very common during humid weather because it is a water-bourne disease. As its name implies, small black spots form on leaves and stems, eventually causing the leaves to drop and weakening the plant.
Treatment: Choose black spot resistant varieties and be meticulous about sanitation. Water the roots of the rose, avoiding the foliage. Water in the morning, so that splashed leaves have time to dry off. If Black Spot is an annual problem, try a dormant spray of lime sulfur at the end of the season and again in early summer. Once Black Spot appears, it is hard to stop. Neem oil and Sprays containing Potassium bicarbonate are somewhat effective.

Downy Mildew:

  Downy mildew is a very serious disease that spreads rapidly and can defoliate a rose plant in days. It is not as common as Black Spot and favors cool, wet weather. Purple spots with yellow edges form , often on the veins on the top side of the leaves and along the stems. Pale gray fuzz can form on the under side of the leaves. The leaves will eventually become brittle and fall.
Treatment: The good news is that Downy Mildew often clears up with the weather. To reduce the chance of Downy Mildew, practice good garden sanitation and keep the rose plants well pruned for air circulation. As with other diseases, a dormant spray may help.


A Rust infection is easy to spot. Small orange pustules spots form on the undersides of the leaves. This fungus can also cause defoliation. Rust is most prevalent when nights are cool.

 Treatment: Treatment of Rust is similar to treatment of Black Spot, above: Good sanitation and a preventative dormant spray after pruning. Once infected, remove all infected leaves and try Neem oil for control.

 Mosaic Virus:


Once a rose is infected with Rose Mosaic Virus, there’s not much to be done except check with the nursery for a replacement. Rose Mosaic Virus shows up as yellow mottling on leaves and deformed new growth. It can stunt growth or it can be a mild infection.

If there are only a few affected leaves, the plant may continue growing and blooming fine. The really good news is that it won’t spread to your other roses.

Stunted or malformed young canes

Known as powdery mildew, this is a fungal disease that covers leaves, stems and buds with wind spread white powder. It makes the leaves curl and turn purple. Spray with Funginex or Benomyl to treat this fungal disease.

 Blistered underside of leaves


Known as rust, this disease is characterized by orange-red blisters that turn black in fall. It can survive the winter and will then attack new sprouts in the spring. Collect and discard leaves that are infected in fall. a Benomyl or Funginex spray every 7-10 days may help.

Malformed or stunted leaves and flowers

This is caused by spider mites. They are tiny yellow, red or green spiders found on the underside of leaves where they suck juices. The application of Orthene or Isotox may help in treating this infestation.

 Weak and mottled leaves with tiny white webs under them


This is caused by aphids. They are small soft-bodied insects that usually brown, green or red. Often clustered under leaves and flower buds, they suck plant juices from tender buds. Malathion or diazinon spray may help roses to survive these bugs.

 Flowers that don’t open or are deformed when they open.

Thrips could be the reason behind this problem. They are slender, brown-yellow bugs with fringed wings that also suck juices from flower buds. Cut and discard the infested flowers. Orthene and malathion may also treat this problem.


Remember that roses are hungry feeders that require much fertilizer to become healthy bushes.for any question related rose you can ask ………


Share this article with your friends if you found this information helpful.



4 thoughts on “Dealing with Rose Diseases

  1. This is a nice, helpful article on roses, and as you rightly pointed out, they do have a reputation of being pretty snooty. Mine have had everything ranging from aphids, spider mites, mealy bugs to black spot and rust, and over a period of years and after having lost a couple of rose bushes, I realised one thing about them – Never leave them underfed. They are known to be voracious eaters and you need to keep them fertilized or these problems start affecting them too much. A healthy rose bush can ward off a lot of problems on its own, if its fed well and in the sun. This post will definitely help people with their gardening skills.


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