How to Treat Downy Mildew Naturally on Your Plants?
Quick answer: downy mildew is recognised by oily yellowish spots on the upper side of the leaves and a greyish down underneath, especially in wet weather. As a preventive measure, spray horsetail fermented extract every 2 weeks from the start of spring; as a cure, remove the affected parts immediately and treat with horsetail fermented extract or, as a last resort, Bordeaux mixture. Downy mildew spreads very quickly in damp weather, so it is important to act at the first symptoms.
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How do you recognise downy mildew?
Yellowish to brownish spots with an oily appearance show up on the upper side of the leaves, with a whitish to greyish down visible on the underside in damp weather. The disease spreads very rapidly in warm, humid conditions, typically after a spell of rain followed by heat.
The natural protocol in 3 steps
- Remove immediately the affected leaves and stems, without composting them, to limit the spread of spores.
- Spray horsetail fermented extract, which is rich in silica, over all the foliage, as a regular preventive treatment or as a cure at the first signs.
- Improve air circulation between plants to reduce the stagnant humidity that encourages the fungus to develop.
How do you prevent downy mildew before it appears?
Preventive sprays of horsetail fermented extract every 2 weeks from the start of spring strengthen the plant's natural defences. Also avoid watering the foliage and favour watering at the base, especially in the late afternoon or evening.
Frequently asked questions
Does horsetail fermented extract cure a plant that is already badly affected by downy mildew?
It slows the progression and strengthens the defences, but parts that are already necrotic do not recover; removing them remains necessary alongside the treatment.
Does downy mildew spread quickly between plants?
Yes, very quickly in damp weather, through spores carried by water and wind; isolating or preventively treating neighbouring plants is recommended as soon as the first cases are detected.
Should you water differently during periods when downy mildew is a risk?
Yes, favour watering at the base of the plant rather than over the foliage, ideally in the morning so that the leaves dry quickly if any dampness remains.