Powdery Mildew on Roses: Combat Detect &

A white or gray coating on roses is often a sign of powdery mildew. We reveal how to recognize downy and powdery mildew on roses and how to combat it with home remedies and the like.

The rose (Rosa) is one of the longest-cultivated ornamental plants and is more diverse than almost any other plant. Several thousand varieties with a wide variety of flowering and growth forms adorn German gardens. But there is a widespread pathogen that can threaten the flowering splendor from the beginning of May. Strictly speaking, there are even two pathogens: powdery mildew and downy mildew.

Powdery mildew on roses

First of all, it is important to know how rose powdery mildew (Podosphaera pannosa) and rose downy mildew (Pseudoperonospora sparsa ). Not only do their names differ, in fact the two mushrooms are only distantly related. While downy mildew belongs to the egg fungi (Peronosporomycetes), powdery mildew is assigned to the sac fungi (Ascomycota). Their survival and reproduction strategies are different, so the type of fungus you are dealing with is important for successful control.

Recognizing powdery mildew on roses

• Mealy-white coating on the roses, partially or completely covering the top and bottom of the leaf. This coating can be easily wiped off with your fingers and thus distinguished from limescale stains or the like.
• The white coating can also be found on shoots and buds. However, the coating does not occur on the woody stem of the rose.
• You can use a magnifying glass to see small arms (carriers of conidia) which carry several balls, the so-called conidia. These are spores to spread the fungus.
• What you don't see: The fungal mycelium - i.e. the network - grows through the stomata into the leaf and absorbs nutrients from the upper cell layers.
• If the infestation is severe, the leaves will turn red and curl up or even be shed.
• The growth of the shoot tips and the formation of deformed leaves can also occur, and plant growth is also inhibited.

Control of powdery mildew on roses

Because powdery mildew does not overwinter in the leaves but only under the bud scales of the younger shoots, pruning roses in spring is particularly important to combat it. Apart from the general preventive measures such as good rose fertilization and the right location, effective home remedies should be used in a targeted manner even with a weak infestation. We will present these to you below. In the case of a severe infestation, sometimes only professional pesticides can help - but here too we have compiled biological preparations for you below.

Downy mildew on roses

Detecting downy mildew on roses

• Brownish-red or purple spots can be seen on the top and bottom, often located between the leaf veins of the plant.
• In humid conditions, a thin gray-white mold growth is formed on the underside of the leaf. With a magnifying glass, the individual spore carriers can be identified, each of which only carries a single spore. The fungus uses these spores to spread.
• Shoots can also become infected and then show reddish spots and possibly a lawn of mould.
• If the infestation is severe, leaves are shed.
• Buds can dry up.
• Plant growth is inhibited.

Tip: Downy mildew is much less common on roses than powdery mildew. It is also not usually confused with powdery mildew, since the symptoms observed are very different. Downy mildew never shows the distinctive white coating on rose petals.

Control of downy mildew on roses

Because the spores of downy mildew overwinter in the leaves and shoots of the plant, removing the foliage after the leaves have dropped in autumn is particularly important. In addition, the annual pruning and care cut of the roses should definitely be done generously at the first shoot. Leaves and shoots are disposed of in the residual waste or burned. If all precautions have not helped or if you were unfortunately neglected, there is a small selection of home remedies and biological pesticides for targeted control of the fungus. We will present both options to you later.

Home remedies against powdery mildew on roses

Just like powdery mildew on cucumbersThere are also a few effective home remedies for powdery mildew on roses:

• Treatment with milk: A mixture of milk and water (ratio 1:9) is sprayed on the leaves daily when an infestation occurs. The powdery mildew fungus is attacked by the lactic acid bacteria and, in the best case, completely suppressed. It remains to be seen whether the milk mixture is just as effective against downy mildew.
• Treatment with baking powder: The potassium (hydrogen) carbonate contained in baking powder is strongly basic and makes life difficult for both powdery mildew and downy mildew. The effect of a 0.5% solution with water (5 grams in one liter of water) has already been confirmed in several tests.
• A reader of our magazine uses chamomile tea as a preventive measure. The essential oils contained in chamomile also probably inhibit the initial development of the fungus, so that the infestation does not appear in the first place.
• According to scientific studies, spray mixtures made from fennel and horsetail also have an effect as long as the mildew infestation is not too severe.

Important: The above methods are used successfully by some hobby gardeners, others can see no effect. However, it is definitely worth trying out home remedies for a mild infestation or as a preventive measure and saving yourself the money for sprays.

Other remedies against powdery mildew on roses

You don't have time to prepare a spray liquid or your roses are already badly infested? Then you still have the option of combating powdery mildew on roses biologically. Effective remedies include Equisetum Plus, which consists primarily of field horsetail extract. Wetted sulfur products from various manufacturers are also very effective against fungi, but can also harm beneficial organisms if the dosage is too high. The same applies to copper preparations, which may be used in organic farming, but accumulate in the soil to alarming concentrations over time.
If these agents are used correctly, even a stronger mildew infestation will soon disappear. Preventative measures should then be taken in autumn and next spring to prevent a renewed severe infestation.

Prevention of powdery mildew on roses

To prevent your roses from being attacked by any type of harmful fungus in the first place, you can follow a few tips:

1. Roses absolutely need a sunny spot with somethingair movement. A good location already prevents many diseases and pests. To ensure that the foliage dries quickly, roses should stand as freely as possible and not under the eaves of trees or buildings.
2. Don't plant roses where previously roses grew. Incidentally, almost all fruit trees and strawberries also belong to the rose family.
3. Your rose should be optimally nourished and comfortable in your patch of soil. You can achieve this with the help of high-quality potting soil such as our Plantura organic potting soil and gentle, primarily organic fertilizers such as Plantura organic rose fertilizer.
4. When watering, make sure you only hit the bottom and not the leaf. Fungal spores require a minimum amount of liquid to germinate and penetrate the leaf.
5. When choosing new roses for your garden, you can specifically choose ADR roses. The ADR test (General German Rose Novelty Test) tests the aesthetic and he alth properties of roses over a period of several years.
6. There are also new breeds that are resistant to powdery mildew fungi. For example, the apple blossom, heather dream, palm garden Frankfurt and summer wind varieties have proven to be resistant.

Tip: While downy mildew depends on a high temperature and leaf moisture during germination - 20 °C and dripping water are optimal - powdery mildew develops best in dry conditions and Sunshine. It only needs the dew water of the cool night and will even be damaged by dripping water.

Would you like to admire the most beautiful and most blossoms every year? We will explain to you how rose pruning and the perfect rose fertilization work.