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Powdery mildew on roses – what can be done and what home remedies are suitable to combat the disease?

Roses are one of the most popular garden plants and are not without reason called the queens of flowers. Surely you have invested a lot of time and effort in caring for them, so it is all the more annoying when you suddenly notice some problem with your beloved plant. In addition to aphids, one particular fungal disease in particular is a common nuisance – powdery mildew on roses. Do you suspect that your rose bush has just been attacked by it? We explain how you can recognize the fungal infection and what you can do to save your plant – without any harmful chemicals!

True or downy mildew on roses – what is the difference?

Proper care for rose bushes and prevent fungus

Both are fungal diseases , but they differ in their characteristics and the causes of their development are also different.

Powdery mildew forms a coating on the leaves, which is silvery to gray in color. In addition, the fungus deforms the tips of the shoots. It develops mainly during major temperature fluctuations and, more precisely, when temperatures are warm during the day, but fall more sharply at night, causing dew. And it is precisely this humidity that the fungus likes. Powdery mildew is also the one most likely to attack roses.

Downy mildew attacks the leaves, not the shoot tips

Downy mildew, on the other hand, is characterized by yellow discolored leaves, and on the underside, in turn, a grayish coating reminiscent of mold develops (not to be confused with another disease – gray mold). This variant also arises from the combination of warm and humid, but these two conditions occur simultaneously. So if it’s nice and warm outside and then rain comes along, those are the perfect conditions. This also happens quickly in greenhouses.

What helps preventively?

Powdery mildew on roses - What helps against the fungal infection

It is therefore only logical that the best preventive measure is to avoid the environments described above. This already starts with the right location, which should meet the requirements of the rose. Optimal ventilation, so that moisture can dry quickly, is another important factor. For roses, it is important to refrain from mulching with bark mulch, as this promotes fungal growth. Underplanting with other, lower plants is a better choice here, as this also ensures good aeration. Do not overdo it with the nitrogen when fertilizing. It promotes the formation of many new leaves, which in turn increases the susceptibility to mildew.

What to do about powdery mildew on roses?

Powdery mildew on roses - How to recognize the most common disease.

But what if it is now already too late? What helps with powdery mildew on roses and can save the bushes as soon as possible? It depends, first of all, on the species:

Combat powdery mildew fungus.

Correctly treat rose with powdery mildew - means against the infection

As already mentioned, the actual fungal attack is on the shoot tips and buds. This is also where the fungus can easily overwinter, so low winter temperatures won’t help you. Instead, pruning the roses in the spring comes to your rescue, disposing of the cut shoots (in the residual waste or burned). But even before that, you should take action against even the slightest infestation, before it spreads further. Home remedies are then effective. If these do not work, resort to means from the trade. There is also a sufficient selection there, which is not harmful to the environment.

Fighting downy mildew fungus

Rose leaves with false mildew fungus - dispose of fallen leaves in the fall

The fungus in this case affects the leaves. So, as soon as the rose bush has shed its leaves in autumn/early winter, take action. You should dispose of this immediately (in the residual waste or burn it) to prevent further spread of the fungal spores and to rid the already infested plant of them. However, if you notice a fungal infestation again next year, you can resort to home remedies. If these do not have the desired effect, resort to environmentally friendly means from the store.

Home remedies against mildew on roses

Home remedies for powdery mildew on roses - how to fight fungal infection without chemicals

Natural remedies for powdery mildew on roses are not one hundred percent effective, but they can be a good method for light infestations, i.e. in the initial phase, and also as a preventive measure. The following may be helpful:

  • Milk is effective both for existing powdery mildew and as a preventative. Mix raw milk or whole milk with water in a 1:8 ratio and spray the rose bushes with this solution. It is important that you do not take UHT milk, because it no longer contains the required lactic acid bacteria and would therefore not work.

Lactic acid bacteria help against a light infestation with fungal spores

  • Dissolve a packet of baking soda in two liters of water and add 20 ml of canola oil. Spray it on diseased plants as well as on healthy ones as a preventive measure. Especially after rain, the treatment should be repeated, as this washes off the agent. Effective in this home remedy is the alkaline reaction that disturbs the fungus. Again, keep in mind that the effect is relatively weak and works at best for light infestations.
  • Algal lime has a high pH that prevents spores from multiplying. So if you’re looking for a fungal disease remedy that is harmless, it works best. A powder sprayer is best for spreading the lime finely on all leaves and plant parts. However, before you diligently apply the remedy to all your plants, keep in mind that plants that require acidic soil and are sensitive to too much lime will not tolerate it.

Powdery mildew on roses, what to do - Mix baking powder with water and rapeseed oil