Rust on roses results from the rose rust fungus disease and first appears on the undersides of leaves
Fungus diseases are always serious for your flowers. It can occur on roses anywhere in the right conditions and if left untreated, it can be fatal for your plants.
As always, it is easier to avoid diseases before you have to fight them.
In cases of infestation with rust fungus, yellowish to brown spots form on the leaves. On the underside, yellow, then rust-brown, later black pustules develop with rust spores. The leaves may curl, turn yellow and fall off.
The first signs of the disease occur in the late summer on the lower branches of the plant.
In spring, when the fungus was able to overwinter, on the shoots bright orange-red calluses can be found.
The roses display a reduced growth and produce few or no blooms.
Loamy and compacted soils support the disease. The soil should therefore always be well-aerated.
To support poor soil, mixing in some sand and compost will be a huge advantage for the overall health of the plant. In addition, a good potassium supply is important.
A sunny location with good circulation is, of course, always the best guarantee for fungus-free and healthy roses.
The aerial parts of plants, such as leaves and canes must be kept as dry as possible. Water the bushes on the ground, avoid overhead watering and keep the bushes tidy by always removing dead canes.
Some rose varieties are more susceptible to diseases than others. Avoid problems by always buying good quality.
Once the plants have been infected by rust, you should react immediately.
Infested roses need treatment to combat any still existing spores. Either you spray the plants with an appropriate fungicide, or you try it in an organic way.
Ortho Rose Pride Rose & Shrub Disease Control would be a very useful product to treat rose rust fungus.
If the roses are not severely infected, an organic treatment would be my first choice. I already have tried Neem oil and was very pleased with the outcome.