It is a common misunderstanding that roses have high maintenance needs. However, growing roses is not more difficult than growing any other flowering plant. You should always plant your rose in a sunny spot with proper drainage. Fertilize plants regularly and water each plant evenly for beautiful flowers.
Ensure that you prune your rose bushes at the beginning of spring. Observe your plants regularly for signs of rose diseases. If you are looking to grow roses in your garden, here is a guide to some rose diseases you should be aware of:
Black spots are one of the most common rose diseases caused by a fungus called Diplocarpon rosae. Cool and moist weather during fall allows this disease to spread rapidly since moisture is unable to escape from the leaves and into the atmosphere. Evaporation during the summer helps curb the growth of this disease.
Black spot does not kill roses, but it makes plants susceptible to other infections. Black spots often occur near a plant’s base and gradually infect the rest of the plant. You will know if your plant has this disease if the leaves have a black or purplish hue on them. It is vital to treat this disease during its early stages—once infected, this disease can reappear each year.
Black spot can be eradicated by removing and disposing of all infected leaves. Ensure that the foliage stays dry since the fungus can germinate on a wet surface. Fungicidal sprays can be used every 7 to 14 days to prevent the spread of the disease to new leaves. You can also replant your rose bush with more disease tolerant varieties like ‘Simplicity’, ‘Bonica’, ‘Fortyniner’, and ‘Grand Opera’.
Among all rose diseases, Botrytis Blight causes the most visual floral damage. This disease turns petals dry, brown, and crispy in structure caused by the fungus Botrytis cinerea. It also affects buds, stems, and leaves. Hot and humid summers cause this disease and ruin the blooms of flowers.
Botrytis Blight can be prevented by keeping your rose bushes in dry and sunny weather. Destroy all affected stems, flowers, and canes. Avoid wounding plants while pruning them and ensure proper air circulation is occurring by maintaining enough space between rose plants.
Cankers is a fatal fungal disease, which is a consequence of pruning with unclean equipment. Cankers can turn the canes of roses black, spread to the crown of the rose, and cause plant death. This disease happens especially during monsoon and winter months.
There are three types of cankers that affect roses: brown canker, stem canker, and brand canker. Brown canker develops in the form of tiny, reddish-purple spots that mature into a brown or a black color. Stem canker is visible on the plant’s bark and may range from a yellowish to a reddish color. Brand canker consists of a reddish color on the canes like a brown canker but this canker has a distinct brown center.
Cankers can be avoided by using sharp and clean pruners for gardening. Always clean your pruning shears with a disinfectant or a 100% bleach solution since the pathogen spreads on dirty tools. Remove the entire canker infected stem by cutting it down to almost two inches beneath the lowest
canker. Apply an organic fungicide on all sides of the stems every two to three weeks throughout the growing season to prevent cankers and other. rose diseases
Crown Gall is a commonly occurring bacterial disease among rose bushes around the world. Agrobacterium tumefaciens causes this infection by injecting a tumor-inducing gene into the plant genome. This disease’s symptoms include weakness, stunted growth, dieback of rose shoots, discoloration of leaves, and increased susceptibility to other infections.
It is not possible to completely eradicate this disease but preventive measures can be taken to curtail its formation. Purchase healthy looking plants and grow them in soils with no former history of crown gall. Use sterilized pruning equipment and insecticides to reduce wounds on plant tissues. If your plant is infected with crown gall, remove the whole plant and the surrounding soil before replanting in the same area.
Powdery mildew is caused by the Podosphaera pannosa fungus and is a conspicuous white growth on rose plants. It affects all aerial parts of the plant and survives well in high humidity, areas with low air movement and poor soil quality. Powdery mildew grows in garden plants other than roses.
Common mildew symptoms include white fungal growth on shoots and leaves and discoloration or distortion of leaves. Flower buds that are heavily infected may fail to open properly. Mildew growth may be spotted on stems, petals, calyces, and flower stalks.
Powdery mildew can be prevented by choosing high quality soil for planting roses. Areas with plenty of sunlight and good air circulation are ideal. Soil that is properly irrigated, fed with nitrogen, and spread with mulch are beneficial for avoiding mildew. Chemicals such as fungicides or a combination of insecticide and fungicide should be applied every two weeks.
Rose Rosette is a viral disease which generates a red pigment underneath leaf veins in a plant. This is followed by an increase in growth of shoots, and deformed leaves. Petioles become shorter, leaves smaller, and lateral buds produce deep red shoots. This infection grows rapidly through the summer as mites travel in the wind and affect new plants.
Rose Rosette can be prevented by planting multiflora roses far from ornamental ones. Plant Rose Rosette resistant shrubs and prune them extensively the first year to remove mites and infected tissues. You can also apply insecticidal soap in measured quantities to remove the mites.
Nine species of fungus cause this disease in roses. Rust usually appears in spring and fall but can appear in the summer as well. It can be spotted as orange or rust-colored patches on leaves that grow bigger as the infection worsens. Rust infected leaves may fall off from the bush or defoliate.
Rust can be treated by ensuring rose plants have adequate space between them and that proper air circulation is taking place. Thorough watering of rose plants is crucial, and punctual cleanup of fallen leaves can help minimize the proliferation of this disease. You can also buy rust-resistant rose plants which do not contract this disease.