Powdery mildew looks ugly and can cause enormous damage to the affected plant. Act quickly and prevent mildew infestation!
A whitish coating on the leaves? The leaves are curling up and the plant is no longer growing as usual? Then it could be powdery mildew. Various types of mushrooms are summarized under this name. There are about 100 species, many of which only affect certain plants. In general, a distinction is made between genuine and downy mildew. Both types of mushrooms have similarities and differences. In any case, the hobby gardener is called upon to take countermeasures. Otherwise, the entire plant may die. Find out below how you can identify, distinguish, combat and prevent powdery mildew.
Powdery mildew and downy mildew
The powdery mildew is a sac fungus. The fungi, which come in 19 genera, need a host plant to survive. There, the fungi usually settle on the upper side of the leaves and are clearly visible there as a white coating reminiscent of flour. The coating remains superficial, does not penetrate into the deeper layers of the leaves and can easily be wiped off with your hands. Nevertheless, powdery mildew damages the plant tissue, because the fungus forms suction cups, which attach themselves to the cell wall and withdraw water and nutrients from the leaves. The principle is roughly comparable to that of the aphid.
Tip: Powdery mildew is a "fair weather fungus" and is particularly common when the weather is warm and dry.
The downy mildew is one of the egg fungi. This species is actually not a fungus, but rather related to algae. In the middle of the 19th century, bottle mildew began to cause massive damage in horticulture and agriculture in Europe. Downy mildew also affects the underside of the leaves and penetrates the leaf tissue. This type of fungus is initially recognizable on the underside of the leaves, where a grey-blue coating forms. If downy mildew remains undetected, yellow-brown spots appear on the upper side of the leaves. Affected plant parts can no longer obtain sufficient nutrients, wither and eventually fall off.
Tip: Downy mildew is a "bad weather fungus" and thrives particularly well in a warm, humid environment.
Downy and powdery mildew - differences
| Powdery mildew | Downy mildew |
| white coating on the upper side of the leaves | white to grey-blue film on the underside of the leaves |
| Fungus does not penetrate deeper into the surface of the plants | Fungus penetrates deep into plant tissue |
| dry and warm environment is preferred | warm and humid conditions are preferred |
How to identify powdery mildew on affected plants:
- white to grey-blue mycelium on leaves and shoots
- flour-like coating on the top of the leaf
- yellow-brown spots on the upper side of the leaf
- Plant grows poorly
- Leaves change color and curl up
- Fruits burst open and rot
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Powdery mildew - aggressive and not choosy
The whitish coating on the upper side of the leaves appears rather harmless at first glance. But if you don't act in time, other parts of the plant can be affected with the shoots, flowers and fruits. The lack of nutrients leads to growth disorders in the affected plants.
Tip: Strawberry plants or vines show a reddish discoloration instead of the white coating.
Although powdery mildew is aggressive, it rarely kills the entire plant. The fungus is not choosy and can actually take possession of all green plants.
The following flowering plants and perennials are particularly susceptible to powdery mildew:
- Phlox
- Aster
- Sunflower
- Larkspur
Powdery mildew can also spread to a whole range of woody plants:
- Apple Tree
- Roses
- Maple
- Hawthorn
- Barberry
Some powdery mildew genera and their preferred hosts:
- Oidium lycopersicum - Tomato
- Podosphaera pannosa - Rose
- Podosphaera leucotricha - apple
Downy mildew - frequent guest in the greenhouse
Downy mildew also first settles on the leaves. Only there he findsthe stomata, which enable it to penetrate into the tissue of the plant. Initially, a blue-grey coating appears only on the underside of the leaves. In the course of the infestation, affected plants show conspicuous growth disorders. Downy mildew usually occurs in greenhouses or conservatories, as the humidity here is high and the conditions are ideal for the fungus to spread. Downy mildew primarily affects crops.
Tip: The fruits of plants affected by downy mildew should not be eaten, but disposed of as soon as possible.
Some genera of downy mildew and their preferred hosts:
- Bremia - Salad
- Plasmopara - carrots, celery, parsley
- Peronosporaan - onions, peas, strawberries
Control powdery mildew
Home remedies against powdery mildew
If you have noticed mildew infestation, act immediately and remove all affected parts of the plant. There are also some home remedies that have proven effective in combating powdery mildew.
A mixture of water and milk is extremely effective. You will achieve good results with this, especially with a rather light infestation. Make a solution by mixing 1 part milk to 9 parts water. This solution can now be sprayed onto the affected plants. The bacteria contained in the lactic acid take targeted action against the fungus. If you don't have milk at home, you can use buttermilk or whey.
Warning: This home remedy works very well against powdery mildew, but is often ineffective against downy mildew, since the undersides of the leaves are primarily affected and these are difficult to reach.
Mildew can of course also be combated with the help of baking powder. Baking soda reacts with water and a weakly alkaline environment is created, which the fungus does not tolerate well. For the application, a pack of baking powder is mixed with 20 ml of rapeseed oil and two liters of water. This solution is also sprayed on the affected parts of the plant.
Fighting powdery mildew with plant power
Garlic is also a proven weapon against powdery mildew. The active ingredients in garlic are not tolerated by the fungi. You can make your own garlic brew to treat infested plants or to prevent the spread of mildew:
- cut five cloves of garlic
- Pour a liter of boiling water over the garlic
- let the brew cool down
- the garlic can now be removed
- the brew is poured into a spray bottle
- The plants are now sprayed thoroughly, if possible for several days in a row
Natural predators against powdery mildew
The ladybug not only welcomes aphids on the menu, the busy insects also do not disdain powdery mildew. Ladybugs can actually be found in every garden. In the case of a stubborn infestation, you don't have to leave this to chance, you can also purchase the larvae of two-spot ladybirds from garden retailers and then release them in the garden.
The larvae attack the fungus immediately and pupate after about two weeks. A week later, the ladybugs hatch and continue fighting the powdery mildew. Once the ladybugs have reproduced, the eggs are laid in the immediate vicinity of the fungal infestation. This closes the circle and you have taken care of a good prevention against new fungal infestation.
Note: The twenty-two spot ladybug only eats powdery mildew but is difficult to obtain commercially.
Last resort - chemical pesticides
If the infestation is already advanced, you will probably reach your limits with the home remedies mentioned. In order to save the plant, chemical pesticides should be used. These are usually made on a sulfur or copper basis. Contact fungicides have a lethal effect on the fungus. Chemical agents act on the entire plant and are therefore more effective than an agent that is only sprayed on. However, the pollution of the soil and disturbances in the natural balance of the biosphere should primarily lead you to resort to biological measures.
Prevent powdery mildew
The best way to prevent powdery mildew is to strengthen plants. This can be done with a whole range of products. When doing so, preferably use plant-based extracts.
The following have proven themselves:
- Soda
- lactic acid
- Silicic Acid
- Fennel
- anise
You can produce an effective plant extract yourself from knotweed. To do this, dry 20 grams of leaves and boil two liters of water. The water should have a temperature of about 70 degrees. Pour this over the leaves and let it steep for several hours. The extract is used undiluted like irrigation water. You can use the plant with it toosprinkle.
Pruning reduces powdery mildew
If a plant is affected by powdery mildew, all affected parts of the plant should be removed as soon as possible. It should be cut back into the he althy tissue. The plants usually tolerate a radical pruning better than continuing to be affected and weakened by powdery mildew. Affected foliage should not be left in the garden.
Tip: Mildew only reproduces on living organisms, so infested plant parts can be disposed of in the compost.
Plants to protect against powdery mildew
If you plant resistant and repellent plants, they can prevent powdery mildew from spreading and create a kind of protective wall.
These plants prevent the spread of powdery mildew:
- Foxglove
- Chervil
- Basil
- Chives
- Garlic
This is how mildew can be effectively prevented:
- allow sufficient planting distance
- Place plants between resistant species
- remove weeds from the plant regularly
- Provide plants with tonics
- fertilize appropriately, avoid over-fertilization