In fine weather with the subsequent formation of dew, oak leaves sometimes get white spots on the upper side. This is oak powdery mildew, which can be combated with household remedies.
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oak powdery mildew
Powdery mildew on oak trees, also known as oak powdery mildew, is caused by the fungus Microsphaera alphitoides. It is host-specific and only occurs on oak trees, especially in warm and dry conditions. That is why it is also known as the fair-weather mushroom. The fungus very often infests pedunculate oaks.
damage picture
Oak powdery mildew shows up as a white, powdery growth of fungus on the upper surface of oak leaves that can be wiped off – in contrast to downy mildew, which only affects the underside of the leaf and cannot be wiped off.
Oak powdery mildew later turns brown. Some shoots are also covered by the white coating. A heavy infestation with oak powdery mildew leads to deformed shoots and curled leaves that dry up. Growth disorders can also occur later. Fruit can burst open and become moldy. In the worst case, the whole tree dies.
causes
- too dry climate
- wrong location
- too little water supply
- missing nutrients
- over-fertilization
countermeasures
Oak powdery mildew is best combated with home remedies on young trees. With mature oaks, the undertaking is very difficult.
To cut
- Cut off affected leaves, shoots and branches
- Put clippings in the residual waste
- or burn cut branches
predators
There are some species of ladybugs that eat the white powdery mildew of oak leaves. The larvae of the ladybugs are available in specialist garden shops and can be applied to the oaks in a targeted manner.
raw milk
- Mix raw milk with water in a ratio of 1:9
- Pour the mixture into a spray bottle
- Spray affected parts of the plant several times a week
Natron
Sodium bicarbonate, known as baking soda, is another home remedy that can be used to fight oak powdery mildew. It is mixed with rapeseed oil and water.
Recipe:
- 50 grams of baking soda
- 2 liters of water
- 20 milliliters of rapeseed oil
When combined with water, however, baking soda shows a weak alkaline reaction. Oak powdery mildew doesn’t like that very much. Spray the mixture with a spray bottle several times a day at intervals of 14 days on the parts of the plant affected by white spots.
Prevent
A few preventive measures can prevent white spots on oak leaves.
Resistant Varieties
- only use oak trees that are resistant to powdery mildew for new plantings
- allow the oak trees sufficient sunlight and air
mulch soil
Since a well-mulched soil can prevent the oaks from becoming infected with powdery mildew, it makes sense to spread wood chips or chopped material on the soil as early as spring. This not only reduces evaporation, but also prevents the leaves from being wetted with water when watering.
Pour right
To avoid powdery mildew, the trees should be watered from below. Therefore, give the water directly to the roots. Water only when the soil has dried and only water in the early morning and evening hours.
Cold water extract from field horsetail
- Pour 1 liter of water over 100 grams of dried field horsetail
- Leave for 24 hours
- then stir well and strain
- pour into a spray bottle
- Spray infested parts of the plant several times
- additionally pour diluted 1:10 with water
frequently asked Questions
Yes, you can also use algae lime to combat powdery mildew on oak leaves. To do this, sprinkle it finely over the leaves as soon as the first white spots appear. The high pH value of the algae lime prevents the fungal spores from germinating.
No, the treated UHT milk no longer contains any lactic acid bacteria and microorganisms that can fight powdery mildew, as they are killed by the heat. However, raw milk still contains all the important substances against the fungus.
