How to Cure Rose Plant Diseases

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By Lori Olson
eHow Contributing Writer

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Roses are beautiful, sweet smelling and hardy in many climates, but also susceptible to diseases. The most common diseases are black spot, rust and mildew; they're all due to fungi and the treatment is the same for all of them: prune away everything diseased, destroy the pruning to prevent re-infection and spray or powder fungicide on the roses. A healthy plant will not be attacked as easily as a plant that is not thriving, so the key is to prevent problems from the beginning.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

Drip irrigation hose
Pruning shears
Rose reference book
Lime-sulfur mixture

Prevention

Step 1

Choose a sunny location. Roses fare well in full sun, in soil that is rich and well-drained, and planted about 3 feet apart. This enables the rose plants to get good air circulation between the plants.
Step 2

Irrigate properly. Roses need a lot of water, but sprinklers allow the plants to get too much water on the leaves. Also, sprinklers encourage some fungi, and with an automatic watering system, drip irrigation works better. Create your own drip irrigation by putting a series of punctures in a buried hose line.
Step 3

Prune and clear. The roses need to be pruned carefully, making sure to remove all of all the clippings; this is especially important when pruning away diseased leaves, flowers and stems since they can still spread an infection.
Step 4

Spray lime-sulfur mixture. In the early spring, the spraying of a lime-sulfur mixture helps to prevent attacks of fungi.

Tips & Warnings

Black spot disease gives black spots on leaves and stems, and is often due to overhead watering and rain; the leaves must be wet for almost eight hours before the fungi can grow. Rust is a disease that gives rust-colored spots on the undersides of leaves, while making the topsides turn yellow or pale green. Mildew comes in several forms, but the most common one creates gray-white fuzz on flower buds and new leaves.
It can be tempting to spray insecticides as a preventive measure, but some insects benefit the rose garden, and killing them will weaken the plants. Once a bug infestation occurs, industrial soap might be an alternative to insecticides. Holes in rose leaves and petals suggest that the roses are the victim of beetles or caterpillars, and they can be picked off by hand, if there aren't too many of them. If the buds are bending over and dying before they're open, trips, tiny insects that attack leaves and buds, are likely present. To get rid of them, prune away everything infected and destroy it before spraying the tops of the bushes.
Be sure to clear contaminated leaves and twigs away from your garden. Clean pruning equipment so as not to spread problems such as mildew.