Unfortunately, the rose is often afflicted by diseases and pests. We show how to recognize the symptoms of the disease and combat them with natural remedies.
Roses (Rosa) have high demands on their location and care. If something isn't right, even the sturdiest variety of roses can get sick. Black spots or a whitish coating on the leaves are often the first indication of a fungal disease. But some pests are also very fond of the queen of flowers. Aphids, cicadas and the like multiply quickly and can sometimes cause serious damage to the roses. In order for your rose to remain he althy and produce many beautiful flowers, it is important to react promptly and correctly. In this article, we will explain how you can identify and successfully combat diseases and pests on roses.
The most common rose diseases
In humid conditions, fungal diseases often afflict roses. Discoloration of the leaves can in turn indicate a nutrient deficiency. Using a few examples, we will explain how you can recognize and successfully combat rose diseases.
Recognize and combat black spot on roses
If you discover gray-black spots in combination with yellowish discoloration on the leaves of your rose, it is probably an infection with black spot, which is also known as black spot disease. This common fungal disease occurs only in roses. The causative sac fungus Diplocarpon rosae multiplies particularly quickly in wet weather with temperatures above 15 °C. Individual infested leaves and plant parts should therefore be removed as quickly as possible and disposed of in the residual waste. You can treat heavily infested roses with a fungicide so that the plants do not lose all their foliage. In our special article we explain in detail how to recognize and combat blackspot and how to prevent it.
Detecting, preventing and fighting powdery mildew on roses
Two different fungal diseases are colloquially referred to as powdery mildew. Powdery mildew on roses (Podosphaera pannosa) can be recognized by its typical mealy coating on the upper side of the leaf as well as on the shoots and buds. Downy mildew fungi (Peronosporales) in turn form dark purple spots and lead to rapid leaf drop. In both cases, you should act quickly to avoid further spread.
Various pesticides for treating powdery mildew and downy mildew are available from specialist retailers. You can also use household remedies such as milk or baking powder to combat powdery mildew. When buying new roses, the choice of variety can also make a significant contribution to the prevention of fungal diseases. We advise you to look out for resistant varieties to reduce the need for crop protection products. If a rose has been awarded the General German Rose Novelty Test (ADR), you can be sure that this rose is resistant to fungal diseases. We have put together a special article for you with further tips on how to identify and combat powdery mildew on roses.
Detecting and controlling rose rust
You can recognize an infestation with rose rust by the yellow-red spots on the upper side of the leaf. Later, yellow-orange pustules the size of a pin appear on the underside of the leaves, which represent the spore deposits of the pathogen. To avoid spreading, be sure to remove fallen foliage from under the rose in the fall. But a sunny, airy location also helps to prevent fungal diseases. In our article on rose rust, we present further measures to effectively combat rose rust.
Detecting and fighting chlorosis on roses
Chlorosis is a lack of the green pigment chlorophyll, which causes the leaf to lighten and turn yellow. The reasons for this can be very diverse. Since the chlorophyll is vital for the plant, you should react quickly at the first sign of chlorosis. A calcium, nitrogen, magnesium, boron or iron deficiency, for example, leads to the yellowingthe leaves. Finding the root cause can sometimes be tricky, especially since fertilization may not be able to fix the deficiency, such as when the soil has an incorrect pH level or there is a nutrient imbalance. However, these are rather special cases. If the leaves of your potted rose show chlorosis, adding fertilizer will usually help to compensate for the lack of nutrients. However, over-fertilization can also lead to chlorosis. In our special article, we explain in detail what you can do to prevent yellow leaves as a sign of chlorosis.
By the way: To prevent a deficiency caused by an incorrect pH value or a nutrient imbalance in the soil, it is best to simply use a predominantly organic fertilizer such as our Plantura organic rose fertilizer. This does not affect the pH value and contains all relevant nutrients in the right ratio.
The most common rose pests
Unfortunately, roses are not immune to pest infestation. The sucking and eating damage caused by the small crawling creatures and their larvae can be quite a problem for the plants. In the following, we explain how you can locate the culprits and fight them successfully.
Control rose aphids
The rose aphid (Macrosiphum rosae) is one of the best-known parasites on roses. It is about the size of a pinhead and comes in the color variants green or yellowish-red. The rose aphid prefers to perch on young shoots and buds, sucking on the sugary phloem sap of the rose.
For starters, try rinsing the rose with vigorous water pressure or wiping the aphids with a damp cloth. Neem oil-based products such as our purely plant-based Plantura organic pest-free neem are particularly effective. We have compiled other helpful tips for combating aphids on roses in our special article.
Rose sawfly detection and control
In the case of the rose sawfly (Caliora aethiops), the larvae are the actual pests. The adults are shiny black with gray wings and reach a size of about five millimeters. From May, the females lay their eggs on the underside of the leaves. The larvae that hatch from them are green and yellow on the underside. They only eat the leafy greenssuperficial, which is why one also speaks of window corrosion. In the case of a severe infestation, only a skeleton of the leaf often remains. Affected shoots should be removed as soon as possible. Regular pruning in the spring helps prevent it. Biological pesticides based on neem oil can help in later stages. Our purely plant-based Plantura organic pest-free neem is a natural and extremely effective solution.
Recognition and Control of Planthoppers
Infestation with leafhoppers (Edwardsiana rosae) can be recognized by the white speckles on the upper side of the leaf. You will probably find tiny, light green insects on the underside of the leaves that suck the plant sap from the leaves. But don't be alarmed if the movement of the leaf causes the little cicadas to jump. In order to prevent an infestation with rosehoppers, you should choose a location for your rose where the sun is not too strong and make sure that your plant has an adequate supply of nutrients. You can find more detailed information on the rose cicada in our special article.
Recognizing and combating rose petals
The rose leaf scroll wasp (Blennocampa phyllocolpa) is most easily recognized by the distinctive damage pattern: leaves curled up downwards. The wasp itself is rather inconspicuous with a size of four millimeters. In warm regions, the symptoms are already visible from April, otherwise from May. In most cases, it remains with individual infested leaves and control is not necessary. In the case of a severe infestation, however, the plant is disfigured and growth inhibitions are visible. The rose sawfly larva resides inside the roll and migrates into the soil in August where it overwinters.
To combat and as a preventive measure, we recommend that you remove the affected leaves along with the caterpillar and dispose of them in the residual waste. Pesticides are usually not very effective because the caterpillar is well protected in the leaf roll.
Rose gall wasp detection and control
An infestation by the rose gall wasp (Diplolepis rosae) is easily recognizable by the very conspicuous galls. The galls are mostlyseveral centimeters tall and sit at the tip of the shoot. Hair-like, green, yellow or reddish colored outgrowths from the bile are very typical. From the end of May, such galls can appear on the roses. The plant will not suffer any significant damage from an infestation. The galls look unsightly in the first place and should be removed as soon as possible to prevent the pest from spreading.
Optimal fertilization is an important basis for hardy roses. You can read all about fertilizing roses in our article on rose fertilizer.