My Mom grows the most beautiful roses. She can take a cutting and insert it in the ground and it grows into another rose bush. Our home is surrounded by them. She loves her Roses like her children and often times they too will get sick. Here is a list of common rose diseases and prevention to help you keep your roses in the best of health.
1. Black Spots on Leaves
This disease is commonly known as black spot. Black spot will cause a general weakening of the plant so that progressively fewer and fewer blooms are formed if the disease is left unchecked. Black spots appear as circular with fringed edges on leaves. They cause the leaves to yellow. It is best to remove the infected foliage and prune the infected branches. Pick up any fallen leaves around the rose as these may still contain the black spores and could spread the contamination. There are various fungicides and sprays purchased at most gardening stores to help prevent or treat this kind of rose disease.
2. 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. This disease is different from other common rose diseases, as Powdery Mildew does not need water. It makes the leaves curl and turn purple. Treat this fungal disease with Funginex or Benomyl.
3. 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. Cutting or pruning the entire rose bush during winter months will help prevent any remnants from developing in the spring.
4. 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. We've also used a spray bottle filled with a mix 1/3 cup vinegar and water solution. Seems to work for any type of mite on any garden plant.
5. 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 can help roses survive this type of bug infestatation.
6. 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. Use Orthene and malathion to treat this problem.
Remember that roses are hungry feeders requiring fertilizer to become healthy bushes. Prune and trim away any diseased leaves and branches will help to keep them blooming. Make sure to read and use fungicide as directed. Most roses do well in the winter, but make sure to feed them with fertilizer to help them survive the winter cold.
