Rose Diseases

Rose Diseases: Combating Symptoms And Pest Infestation

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Unfortunately, the rose is often plagued by diseases and pests. We show how to recognize the symptoms of the disease and fight them with natural means. Roses have high demands on their location and care. If something doesn’t fit, even the most robust rose variety can get sick. Black spots or a whitish coating on the leaves are often the first signs of a fungal disease.

But some pests also take a great liking to the queen of flowers. Aphids, cicadas, and the like multiply quickly and can sometimes cause great damage to the roses. To ensure that your rose stays healthy and can produce lots of beautiful blooms, it is important to react promptly and correctly. In this article, we will explain to you how you can identify diseases and pests in roses and combat them successfully.

The most common rose diseases

Fungal diseases often affect roses in damp conditions. Discoloration of the leaves can in turn indicate a lack of nutrients. Using a few examples, we will explain to you how you can recognize rose diseases and combat them successfully.

Black spots on the leaves are an indication of a fungal disease

Recognize and combat sooty soot in roses

If you see gray-black spots combined with yellowish discoloration on the leaves of your rose, it is probably due to an infection with black spots, which is also known as black spot disease. This common fungal disease occurs only in roses. The responsible hose fungus Diplocarpon rosae multiplies particularly quickly in wet weather with temperatures above 15 ° C. Individual infected leaves and parts of plants 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 of their foliage. In our special article, we explain in detail how you can identify and fight blackened soot and how to prevent it.

Black spots with yellow discoloration are typical of sooty spots

Recognize, prevent and control powdery mildew on roses

Two different fungal diseases are colloquially referred to as powdery mildew. The powdery mildew on the rose ( Podosphaera pannosa ) can be recognized by its typical flour-like coating on the upper side of the leaf as well as on the shoots and buds. Downy mildew fungi ( Peronosporales ) in turn from dark purple spots and lead to rapid leaf fall. In both cases, you should react quickly to avoid further spread.

A flour-like coating on the upper side of the leaf is a sign of powdery mildew

Various pesticides for the treatment of powdery mildew and downy mildew are available in specialist shops. You can also use home remedies such as milk or baking powder against powdery mildew. When purchasing new roses, the choice of variety can also make a significant contribution to the prevention of fungal diseases. We recommend that you watch out for resistant varieties to reduce the need for pesticides. If a rose has been recognized by the General German Rose Novelty Examination (ADR), you can assume that this rose is resistant to fungal diseases. We have put together further tips on how to identify and control powdery mildew in roses in a special article.

Downy mildew can be recognized by dark spots on the upper side of the leaf

Detecting and combating rose rust

You can recognize the 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 also appear on the underside of the leaves, which represent the spore beds of the pathogen. To avoid spreading, remove the fallen leaves under the rose in autumn. But a sunny, airy location also helps to prevent fungal diseases. In our article on rose rust, we introduce you to further measures to effectively combat rose rust.

Yellow-red spots on the leaves are characteristic of rose rust

Recognize and fight chlorosis in roses

Chlorosis is a deficiency in the green pigment chlorophyll, which is why the leaf becomes lighter and turns yellow. The causes for this can be very diverse. Since chlorophyll is vital for the plant, you should react quickly to the first signs of chlorosis. A lack of calcium, nitrogen, magnesium, boron, or iron, for example, leads to the leaves turning yellow.

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Finding the right cause is sometimes not easy, especially because the deficiency cannot necessarily be remedied by fertilization, for example, if the soil has an incorrect pH value 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 make up for the lack of nutrients. But over-fertilization can also lead to chlorosis. What you can do about yellow leaves as a sign of chlorosis, we explain again in detail in our special article.

Lightening of the leaves with dark-colored veins indicate nutrient deficiency

By the way: To prevent a deficiency due to an incorrect pH value or a nutrient imbalance in the soil, it is best to simply use a primarily organic fertilizer. This does not affect the pH value and contains all relevant nutrients in the correct proportions.

The most common rose pests

Unfortunately, roses are also not immune to pests. The sucking and feeding damage of the small crawfish and their larvae can be quite a problem for the plants. In the following, we will explain how you can find the culprits and fight them successfully.

Fight rose aphids

The rose aphid ( Macrosiphum rosae ) is one of the best-known parasites on roses. It is about the size of the head of a pin and comes in the color variants green or yellowish red. The rose aphid preferably sits on young shoots and buds and sucks on the sugary phloem sap of the rose.

Aphids particularly like to attack roses

For now, you should try rinsing the rose with strong water pressure or wiping the aphids with a damp cloth. Agents based on neem oil, such as our purely plant-based Plantura organic pest-free neem, are particularly effective. We have put together additional helpful tips for controlling aphids on roses in our special article.

Recognize and fight rose petal wasp

In the rose wasp (Caliora aethiops ) the larvae represent the actual pests. The adults are shiny black with gray wings and reach a size of about five millimeters. The females lay their eggs on the underside of the leaf from May onwards. The larvae that hatch are green and yellow on the underside. These only eat the leaf green superficially, which is why one speaks of window corrosion. If the infestation is severe, then often only a skeleton of the leaf remains. You should remove affected shoots as soon as possible. Regular pruning in the spring helps prevent this. 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.

The actual damage is done by the larvae of the rose wasp

Recognizing and fighting the rose leafhopper

You can recognize the infestation with rose leafhoppers (Edwardsiana rosae ) by the white speckles on the upper side of the leaf. On the underside of the leaf, you will then probably find tiny, light green insects that suck the sap from the leaves. But do not be alarmed if the movement of the leaf causes the small cicadas to jump. To prevent an infestation with rose leafhoppers, you should choose a location for your rose that is not exposed to too much sunlight and ensure that your plant is supplied with sufficient nutrients.

White speckles and light green to white-colored insects indicate rose leafhoppers

Recognize and fight rose petal wasp

The rose petal wasp (Blennocampa phyllocolpa) is easiest to recognize by the distinctive damage pattern: leaves rolled up at the bottom. The wasp itself is rather inconspicuous with a size of four millimeters. The symptoms are already visible in warm regions from April, otherwise from May.

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Usually, it remains with individual infected leaves and control is not necessary. In the event of a strong infestation, however, the plant is disfigured and growth inhibitions are visible. The larva of the rose petal wasp is located inside the roller and migrates to the ground in August, where it hibernates.

Heavily curled leaves are a clear sign of an infestation by the rose wasp

For control and as a preventive measure, we recommend that you remove the infected leaves including the caterpillar, and dispose of them in the residual waste. Pesticides usually do not have a good effect because the caterpillar is well protected in the leaf roll.

Recognize and fight rose gall wasp

An infestation by the rose gall wasp can be recognized by the striking galls

An infestation by the rose gall wasp (Diplolepis rosae ) is easily recognizable by the very conspicuous galls. The galls are usually several centimeters in size and sit at the tip of the shoot. Hair-like, green, yellow, or reddish-colored growths from the bile are very typical here. 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 primarily look ugly and should be removed as soon as possible to prevent the pest from spreading.

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