Powdery Mildew - Fungal Disease of Plants

In short: Powdery mildew is a fungal disease caused by Erysiphales fungi, recognisable by a white, wipeable coating on the upper side of leaves. It spreads by spores in humid conditions, optimally at 20-24 °C. Remove and burn affected parts, never compost them, and spray preventively from June to August with horsetail or garlic decoction.

Powdery Mildew - Fungal Plant Disease

Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew is caused by various species of ascomycete fungi (lat. Erysiphales). Powdery mildew spreads through spores - by wind or contact. It is one of the most common plant diseases. You can recognize it very early. The symptoms of powdery mildew are very distinctive. Infected plants have white powdery spots on them. These spots appear on both leaves and stems.

The lower leaves of plants are affected the most. The coating on them is whitish and can be wiped off. It usually appears on the upper sides of leaves. However, the disease can appear on all parts of the plant. As the disease progresses, the spots become denser and larger. The affected plant becomes weakened. Its leaves dry out prematurely, become stunted and fall off.

Powdery mildew spreads quickly in humid environments. The humidity can be high but alternating during ventilation. The optimal temperatures for the occurrence and spread of powdery mildew are 20-24°C.

Remove fallen leaves. Affected leaves around plants maintain moisture and thus create a suitable place for powdery mildew to settle and overwinter. In early spring, powdery mildew can attack plants again.

Natural Powdery Mildew Control

If you're not a supporter of chemical sprays, then we have a TIP for you on how to deal with powdery mildew naturally. Prevention is important. This involves using plant decoctions in the form of sprays on plants that we want to protect from powdery mildew. In June to August (i.e., the months when powdery mildew spreads the most), we apply plant decoctions to plants. Apply the spray to both the plant and the soil around it. We can make:

• horsetail decoction - for 10l of water, use 1kg of freshly picked horsetail or 150g of dried horsetail. Leave the horsetail to soak overnight. The next morning, bring the entire mixture to a boil. Cool down and spray with diluted solution 1:5 (1 part decoction, 5 parts water)
• garlic decoction - scald finely chopped garlic, approximately 75g per 10l of water. Leave everything to steep and cool down. Spray with diluted solution.
• BIO protection - concentrate increasing plant resistance

Prevention also includes the use of fertilizers. Fertilize with farmyard manure and compost. If you add nitrogen (some plants need it), then use it carefully. Excess nitrogen makes plants more susceptible to diseases.

Remove plant shoots affected by powdery mildew immediately. By promptly removing affected parts, you can minimize the extent of damage to plants. Under no circumstances compost the cut damaged plant parts, but burn them!

To prevent powdery mildew, spray plants preventively with natural extracts or decoctions. Use a sprayer for application.

Prevention Against Powdery Mildew

If powdery mildew appears on your shrubs, examine them to see if they're too dense with tangled branches and leaves. The inner space of the plant should be ventilated. Don't be afraid to prune the shrub heavily. Powdery mildew is a fungal disease that thrives in humidity.

Prevention also includes sowing resistant plants. Don't sow plants too densely. Always follow the recommended spacing! Plant more sensitive varieties in well-ventilated locations, in sunny and dry spots.

Strengthening plants is an appropriate prevention method. Water with natural extracts or concentrates designed for special plant nutrition.

During summer months, check plants regularly. For plants susceptible to powdery mildew, thin out leaves so the crown isn't too dense. Cut off infected plant parts and burn them.

In autumn, don't be afraid to prune and cut out affected parts of shrubs and trees. However, follow proper tree pruning procedures to avoid causing more harm with improper cuts.

For some plants, mulching or planting on mulch film is a suitable prevention. Always try to purchase healthy and resistant varieties. Follow these principles:

• choose airy locations for plants
• limit nitrogen fertilizers
• remove fallen leaves
• prune excessively dense crowns
• fertilize with mature compost
• soil should be nutritious
• water with rainwater or herbal decoctions
• prevent permanent waterlogging of plants
• mulch with straw or semi-mature compost
• plant proven regional varieties

Last Resort - Fungicides

Application of fungicides (chemical spray against fungal diseases) - save this as a last option if all other methods have failed. Always follow the instructions for use! Use protective equipment - gloves, face mask. Protect your children and pets.

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Author: Hana Michalíková