Powdery mildew (fungus)
Surface changed / modified

Powdery mildew (fungus)

📍
Whole plant, Upper side of leaves, Flowers / Buds
📈
Normal growth, Gradually worsened
White powdery coating Dry / paper-like patches
⚠️ Verwechslungsgefahr

Echter Mehltau zeigt sich typischerweise als weißer bis grauweißer, pudriger Belag auf Blattoberflächen, jungen Trieben und teils auch an Blütenbereichen. Mit fortschreitendem Befall vergilben Blätter, trocknen ein und verformen sich. Entscheidend für die Einordnung ist der sichtbare Oberflächenbelag: Das Problem sitzt außen auf dem Pflanzengewebe und wirkt wie aufgestäubt. Genau das trennt Mehltau sauber von Botrytis beziehungsweise Bud Rot, bei dem das Gewebe im Inneren fault, braun wird und von innen heraus zerfällt. Weißer, oberflächlicher Belag und deformierter Neuwuchs sind für echten Mehltau typisch.

Go to solution

Ursachenforschung: Was ist passiert?

High humidity combined with poor air circulation and significant temperature fluctuations between light and dark phases.

Systemische Einordnung

What is often really behind it

Fungal and pathogen problems usually don't arise by chance. They particularly occur where moisture, air circulation, leaf surface, root environment, and plant vitality are out of balance. Those who want to solve such problems permanently must not only treat the visible infestation but also correct the conditions that enable the disease pressure in the first place. Especially in organic farming, the stability of the entire system determines whether a problem takes hold or is averted.

These points are often related

Botrytis / Bud Rot
Coating / surface changed · Discoloration · Drooping / flaccid plant parts

Botrytis / Bud Rot

Check problem →
Septoria Leaf Spot / Leaf Blight
Spots / Dots · Color change

Septoria Leaf Spot / Leaf Blight

Check problem →
Overwatering / Waterlogging
Drooping / wilting plant parts · Conspicuous growth

Overwatering / Waterlogging

Check problem →
✓ Grow Lab expert solution

The right treatment

Powdery mildew is every grower's nightmare, as its spores spread invisibly throughout the room.

As soon as you spot the white film, you must immediately lower the humidity below 45% and maximize air circulation – every leaf must be moving.

A mixture of organic milk and water (1:8 ratio) has proven effective as a biological weapon against powdery mildew on cannabis. The lecithins and proteins in the milk destroy the fungus's mycelium upon contact with UV light. Spray the affected areas thoroughly every two days.

Alternatively, preparations based on potassium bicarbonate can help. Remove heavily infested leaves extremely carefully, without shaking them, to avoid transferring spores to neighboring plants.

During peak flowering, you should avoid spraying and generously cut out affected areas.

Prevention is key here: Clean your tent with alcohol or H2O2 after each cycle and ensure a consistent nighttime temperature that is no more than 5°C below the daytime temperature.

Expert tools for the next step

After diagnosis, the right decision counts

Not every symptom requires the same next step. If you're specifically looking for the right Living Soil input, our Nährstoff-Finder can help. If you want to strategically align your setup to pot size, experience, goal and nutrients, our Living Soil Navigator will guide you further.

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