Gray-white spots, brown discoloration or fungus-like deposits – the facets of powdery mildew and downy mildew are diverse. Every hobby gardener who discovers this disease in his plants knows that the plant needs immediate treatment. In order to get the symptoms under control, in addition to conventional fungicides, naturopathic approaches and home remedies are available that can effectively combat both powdery mildew and downy mildew. However, preventive measures are also possible. – With the help of different approaches you can protect the plants permanently from the annoying disease.
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The damage caused by the disease
Before starting treatment for powdery mildew, the first step should be to ensure that it is actually the disease. To make an assessment, it is necessary to look at the entire plant and pay attention to changes in color or shape in individual parts of the plant. With regard to the development and the damage, there are differences between real and downy mildew that every hobby gardener should be aware of. In the “real” variant, the symptoms are caused by a hose fungus that lives on the surface of the plant and penetrates the cells with its suction organs. There vital assimilates are withdrawn, whereupon the plant reacts with a specific damage pattern. These include different symptoms:
- white or gray spots on and under the leaves
- in warm weather it can already be seen during spring
- at a later stage, leaves, shoots, buds, flowers and fruits are covered with a floury-moldy layer
- later leaves curl up and flowers no longer open
- The plant takes care of it gradually and shows only sparse growth
- in later stages of the disease, dirty gray or brown discoloration will appear on the coverings
Often times, individual types of sac fungi are specialized in a certain species; for example rose powdery mildew or cucumber powdery mildew is known.
A fungus is also responsible for the symptoms of downy mildew. These are algae fungi pathogens. In contrast to powdery mildew, these live between the cells inside the plants; Their spore carriers protruding from the underside of the leaves then form the floury coverings. Downy mildew forms mainly in damp weather, while the “real” variant prefers dry and warm conditions. The damage caused by downy mildew includes whitish-gray to brownish velvety coatings that mainly form on the underside of the leaves. On the other hand, yellow or brown spots can be seen on the upper side of the leaf, some of which also cover the stems or flowers. The infected parts of the plant die off quickly.
Conventional therapy for the disease
If the infestation is severe, it may also be necessary to use chemical preparations to combat powdery mildew. Powdery mildew should then mainly be worked with fungicides that are gentle on beneficial insects; these include, for example, lecithin preparations or sulfur-based products. The latter are also particularly environmentally friendly. Downy mildew is best treated with special fungicides, which can vary depending on the type of plant. The underside of the leaves in particular should be worked well with the agent. Systemic agents that are absorbed through the leaves and roots are particularly advantageous.
This is how home remedies help against powdery mildew
Both real and downy mildew can be treated excellently with various naturopathic products or tried and tested home remedies. Broths that contain a high proportion of silica are particularly effective; this increases the strength of the cells on the leaf surface. As a result of this effect, the fungal spores can no longer easily penetrate the inside of the leaf, so that the development of infections is greatly reduced overall or even completely prevented. A broth made from horsetail is particularly easy:
- you need 750g fresh field horsetail or 100g dried plants for the mixture
- First put the stalks with five liters of rainwater
- Let the mixture stand for a day
- Boil the mixture for half an hour, then strain and dilute again in a ratio of 1: 5 with water
- If the liquid no longer foams after a few days of rest, it is diluted further with water at a ratio of 1:10
The horsetail broth is applied to the plant every other day. As a preventive measure, a dose every three weeks is sufficient.
Fight powdery mildew with milk and whey
Alternatively, you can try spraying with milk or whey to combat powdery mildew. The microorganisms contained in milk effectively fight the disease and also help the plant to develop resistance to the fungus. This can reduce the chance of powdery mildew infesting the plant again. The correct mixing ratio plays an important role in the preparation of the plant broth. Whey can be diluted 1: 1 with water, while the milk spray has to be less concentrated: This is how you mix five parts of water with one part of whole milk. The finished solution is sprayed directly onto the infected parts of the plant. Treatment takes place twice a week. It is best to choose a day when the chances of a downpour are as low as possible. This avoids
The conventional therapy against powdery mildew often consists of various agents that contain lecithin. This is a tried and tested substance that acts as a pesticide and repellant. With the help of various household remedies, you can prepare a mixture containing lecithin that you apply to the plants:
- Mix 3 packs of baking powder with about five liters of water
- Then work about four tablespoons of rapeseed oil into the solution
- add a squirt of detergent
- Detergent acts as an emulsifier, which ensures that the substances combine optimally with one another
- Then spray the mixture onto the infected parts of the plant
- Repeat the treatment a few times to replace any residue that has been detached from the rain
The interval between the doses should be about ten days. So that the mixture can work well, the solution is best sprayed on in the late evening hours.
The water glass method
So-called “water glass sprays” are often used to combat powdery mildew. This is sodium silicate that is applied to the plants. With this method, the fungi and spores are glued to the parts of the plant. The water glass method is particularly widespread in fruit growing and viticulture. Hobby gardeners should be cautious, however, because the stuck spray is difficult to remove from vegetables, for example. In addition, the remedy is poorly tolerated by numerous flowers.
A very tried and tested biological method of combating powdery mildew is the targeted introduction of beneficial organisms. These include, for example, ladybugs that feed on the fungus. The “twenty-two point”, a yellow ladybug with black dots, is particularly suitable for combating powdery mildew. Trying to bring in sawfly is also worthwhile. When using the biological variant, however, one should take into account that bringing in ladybirds and the like does not provide effective protection against the recurrence of powdery mildew. Therefore, the treatment should also be combined with a plant tonic, for example horsetail broth.
Finally, the targeted spraying of the plants with water also helps against stubborn mildew infestation. A hose can be used for garden plants and larger plants, while indoor plants are best placed in the shower and rinsed off. The annoying fungus can also be removed effectively with small spray guns.
If the plant is very heavily infected with the fungus over a large area, you have to cut out the individual parts of the plant or even destroy the plant.
Optimal care as targeted prevention
In order to protect the plant from powdery mildew infestation, specific measures can be taken in advance. In particular, those who love plants and who have not had so much experience in gardening should pay attention to a specific selection of plants. In the meantime, particularly resistant varieties with a low risk of developing powdery mildew are available for almost all plants. When planting the plant in the ground, you should allow for sufficient space; if the plants are too narrow, the risk of developing powdery mildew is increased. In addition, you should avoid very shady locations with particularly moist soil, as this also increases the risk of developing powdery mildew. You should also keep an eye on the weather: If classic high-pressure weather is announced or the weather is generally determined by strong temperature fluctuations, endangered plants should also be given a plant strengthener. The selection of available home remedies is also large here:
- Horsetail broths, which are also used to combat powdery mildew, are particularly suitable here.
- Fortifying garlic stock, made from three cloves of garlic and 500ml of water, also helps.
- Saline solutions also specifically prevent the infestation.
Particular caution is required when fertilizing the plants: one-sided fertilization in particular can promote powdery mildew infestation. Especially fertilizers that contain a high proportion of nitrogen should be used with extreme caution.
Suitable neighboring plants
But even a clever combination of plants can help to minimize the risk of powdery mildew. Different herbs placed between endangered plants, for example roses, help to ward off the harmful fungus. These include in particular chervil, chives and basil.
It can also help mulch the soil; a substrate enriched in this way is less likely to be attacked by powdery mildew. The following also applies to powdery mildew prevention: watering should not be done in the late evening hours; there is a risk that the plant will not dry out by night. Plants that are particularly moist are at greater risk of developing powdery mildew. In addition, care should be taken not to leave the leaves when watering. It is best to pour the plant directly into the substrate from below.
Regardless of whether the plants are affected by powdery mildew or downy mildew – a natural treatment or therapy with home remedies is almost always worthwhile and should be the remedy of choice in any case. Environmentally friendly spray solutions, some of which can be made from food, are effective and do not interfere with the ecosystem. Only when such agents no longer help can you use fungicides in a targeted manner – but you should use them with great caution and purposefully.