Common rose diseases & pests: identifying, preventing & treating
Unfortunately, roses are susceptible to many pests and diseases. But do not be discouraged! This article provides you with tips and tricks on how to spot rose diseases and pests as well as advice on how best to treat them.
Roses (Rosa) are quite demanding when it comes to location and care. If something is not quite right, even the most robust rose variety can be susceptible to a whole host of diseases and pests. Black spots or a white coating on the leaves are often the first signs of a fungal disease. Aphids, leafhoppers and other insects also like to infest roses and can multiply quickly and cause extensive damage. To keep your roses healthy and flowering, it is important to act in an appropriate and timely manner. Read on to find out how you can recognise and successfully combat diseases and pests on roses.
The most common rose diseases
Humid conditions make roses susceptible to fungal diseases. Discolouration of the leaves can indicate a lack of nutrients. With the help of a few examples, we will explain how to recognise and successfully combat some of the more common rose diseases.
Recognising and treating rose black spot
Rose black spot, also known as black spot disease, causes grey-black spots combined with yellow discolouration on the leaves of the rose plant. This common fungal disease occurs exclusively on roses. The causative fungus, Diplocarpon rosae, multiplies particularly quickly in wet weather and temperatures above 15 °C. Remove and dispose of any infested leaves and plant parts as quickly as possible. Treat heavily infested roses with a fungicide so that the plants do not lose all their foliage. For more information, see our article on how to treat rose black spot.
Recognising, preventing, and combating mildew on roses
There are two types of fungal diseases that are commonly referred to as mildew. Powdery mildew on roses (Podosphaera pannosa) is recognisable by a white powdery coating that occurs on the upper surface of the leaves as well as on the stems and rosebuds. Downy mildew (Peronosporales), on the other hand, forms dark purple spots and leads to rapid leaf drop. In both cases, acting fast is key to preventing the fungus from spreading further.
There are various plant protection products for the treatment of powdery mildew and downy mildew available in specialist shops. You can also use home remedies such as milk or baking powder to treat powdery mildew. When buying new roses, we recommend looking for resistant varieties in order to reduce the need for plant protection products. For further tips, see our article on how to recognise and treat downy mildew on roses.
Recognising and treating rose rust
Rose rust is recognisable by the red-yellow spots on the upper surface of the leaves. Later, yellow-orange pustules the size of a pin appear on the lower surface of the leaves. These are the spore deposits. To prevent the rose rust from spreading, remove the fallen foliage from under the rose in autumn. A sunny, airy location also helps to prevent fungal diseases.
Recognising and combating chlorosis on roses
Chlorosis is due to a lack of the green pigment chlorophyll which causes the leaves to lighten and turn yellow. As chlorophyll is vital for plants to photosynthesise, you will need to act quickly at the first signs of chlorosis. There are many possible causes of chlorosis, including calcium, nitrogen, magnesium, boron, or iron deficiencies, for instance. When your roses start yellowing, finding the right cause is not always easy, especially because the deficiency cannot necessarily be remedied by fertilising if the soil has the wrong pH value or there is a nutrient imbalance, for instance. These are quite unusual cases. If you notice the leaves of your potted roses yellowing, adding a fertiliser will usually help to compensate for the nutrient deficiency. However, over-fertilisation can also lead to chlorosis.
Hint: To prevent any deficiencies caused by the wrong pH value or a nutrient imbalance in the soil, we recommend using a primarily organic fertiliser such as our Plantura Rose Food. This granular fertiliser does not alter the pH value and contains all the necessary nutrients in the right ratios.
- For beautifully flowering roses in pots & flower beds
- Prevents common rose diseases & ensures healthy growth
- Long-lasting fertiliser that is free from animal products - child & pet friendly
The most common rose pests
Unfortunately, roses are not immune to pests. The feeding damage of the small creepy-crawlies and their larvae can cause the plants quite a bit of trouble. Keep reading to learn how you can find the culprits and successfully combat them.
Combating rose aphids
Rose aphids (Macrosiphum rosae) are one of the best-known parasites on roses. They are about the size of a pinhead and vary in colour from pink to green. Rose aphids prefer to sit on young shoots and buds, where they suck the sugary phloem sap from the rose.
To deal with these sap-sucking rose pests, first try rinsing the rose with strong water pressure or wiping off the aphids with a damp cloth. Remedies based on neem oil have proven particularly effective. Find more helpful tips in our article on how to combat aphids on roses.
Recognising and controlling the rose slug sawfly
In the case of the rose slug sawfly (Endelomyia aethiops), the larvae are the actual pests. The adults are shiny and black with grey wings and reach up to about five millimetres in size. The females lay their eggs on the underside of the leaves from May onwards. The larvae that hatch are green with a yellow underside. The so-called rose slugworms eat the surface of rose leaves, known as ‘window paning’. In the event of a severe infestation, often only a skeleton of the leaf remains, which is why sawflies are sometimes known as rose ‘skeletonisors’. Remove affected shoots as soon as possible. Prune regularly in spring to help prevent infestation. Biological plant protection products based on neem oil can help in later stages.
Recognising and controlling rose leafhopper
White speckles on the upper surface of the leaves are a tell-tale sign that you are dealing with an infestation of rose leafhoppers (Edwardsiana rosae). On the lower surface of the leaves, you will find tiny, light green insects that suck the plant sap from the leaves. Do not be alarmed if the tiny leaf hoppers start jumping due to the movement of the leaf. To prevent an infestation of rose leaf hoppers, plant your rose somewhere where the sunlight is not too strong and ensure you are supplying your plant with sufficient nutrients. Find more detailed information in our article on the rose leafhopper.
Recognising and controlling the rose leaf-rolling sawfly
The rose leaf-rolling sawfly (Blennocampa phyllocolpa) has a distinctive damage pattern of curled leaves. At just four millimetres in size, the sawfly itself is inconspicuous. Symptoms are visible from April in warm regions, otherwise from May. In most cases, only a few infested leaves remain, and control is not necessary. However, a severe infestation may cause the plant to become disfigured and will inhibit growth. Rose leaf-rolling sawfly larvae are found inside the rolled up leaves and migrate to the soil in August, where they spend the winter.
To prevent and combat rose leaf-rolling sawfly infestations, dispose of the infested leaves together with the caterpillars. Plant protection products are usually not effective here as the caterpillar is protected in the rolled up leaves.
Recognising and controlling Robin’s pin cushion
An infestation of Robin’s pin cushion (Diplolepis rosae), also known as the gall wasp, is easily recognisable by the very conspicuous galls. The galls are often several centimetres in size and are located at the tip of the shoot. They typically have hair-like, green, yellow, or red outgrowths. Such galls can appear on roses from the end of May. Although the plant will not suffer any severe damage from an infestation, the galls are unsightly and should be removed as soon as possible to prevent the pest from spreading.
