Roses are among the most romantic flowers, but growing them is a chore. No matter how much care you put in them, your beloved rose bushes would eventually be affected with diseases, which you need to remedy as soon as possible before it would get any worse. But before reaching for that fungicide spray, consider treating your bushes with the least toxic solutions possible.
It is a type of fungus that is common in humid weather, mainly because it is a water-borne disease. True to its name, this disease is marked by small black spots on the leaves and stems, which would eventually cause the leaves to drop and weaken the plant.
Treating black spots is especially difficult because once they appear, they are hard to stop. Try preventing the appearance of black spots by spraying your rose plants with lime sulfur at the end of rose season and again in early summer. Neem oil and sprays with potassium bicarbonate may also be effective. If you have difficulty dealing with black spots, consider buying rose varieties that are resistant to black spot. It is best to water your plant on the roots in the morning.
Downy mildew spreads rapidly on your plant and can defoliate your rose plant in days. Unlike black spots, downy mildew prefers to thrive in cool, wet weather. You can distinguish this disease by its purple spots with yellow edges, often on the veins on the topside of the leaves as well as along the stems. Meanwhile, the underside of leaves can be infected with pale gray fuzz, making leave become brittle and fall.
Treating your plant from downy mildew may be relatively easy, as it often clears up with the weather. However, to reduce the chances of your rose plants getting infected, keep the rose plants well pruned for improved air circulation. A dormant spray might alwo help.
Just like its monicker, your rose bush appears to be suffering from rust infection with its orange pustules from the underside of leaves, which would cause them to fall. This disease is most prevalent during cold nights. Treating rust disease is similar to that of black spots. Also, remove all infected leaves and apply neem oil to control the fungus. Preventative dormant spraying after pruning can also help.
This is one of most untreatable diseases that may hit your roses. Once it happens to your rose plant, better buy replacements instead. Rose mosaic virus appears on your rose plants as yellow mottling on the leaves and deformed new growth. It stunts the growth of your plants, but if there are only a few affected leaves, your plant may continue growing and would even bloom. The good part about this disease is that it does not spread to your other rose bushes.