How To: Defeat Powdery Mildew the Organic Way | Organic Lifestyle Co

By Bryan Stralow, editor –

When discovering why your plants are dying off and you look to the leaf or stem material and see a fine white ‘powder’ and necrotic spots underneath, you have discovered why your plant may have decreased in vigour and started to drop its leaves.


Older leaves are most affected by the fungal disease, Powdery Mildew.

Powdery Mildew (PM) is a fungal infection that is caused by stagnant air movement, high humidity and in this case, intense light from an overhead LED greenhouse light, especially when combined with Sunlight. With intense light, on a micro-environment level, comes high heat. So if you are supplementing lighting or growing solely from artificial lights, Powdery Mildew can be caused by ‘too much light’ and obviously a lack of airflow.

Supplemental lighting is very common in greenhouses in order to maintain above average growth rates and therefore optimal harvesting. Powdery Mildew does counter the plants ability to produce. It is wise to maintain constant dry air flow when growing indoors. This in itself will prevent Powdery Mildew from forming. Also, feeding in early morning and evening will also help to counter the High Humidity/ High Light (UVA/ UVB) Level combination. Doing so also prevents refracting and intensifying the light through the droplet of water sitting on top of the leaf which can in actuality help to burn your leaf.

Airflow whilst feeding, in particular foliar feeding, is most important when growing in a static environment such as Greenhouses and Indoor Grow Rooms.

If you discover that your plants have PM, fighting Powdery Mildew without harsh chemicals can be hard. There is a very simple, cost effective method using a diluted Baking Powder and Water mix.

POWDERY MILDEW (Organic Removal Method)

  1. First, grab a spray bottle capable of housing at least 1 litre. In this case, I have used a larger sized bottle that houses 5 litres (2 gallons).spray-applicator-organic-powdery-mildew
  2. Get some Baking Powder from the kitchen and a Tablespoon.spoon-measure-organic-powdery-mildew
  3. Place one tablespoon of Baking Powder to One litre of water.baking-powder-organic-powdery-mildew
  4. Spray on all parts of plant; leaves and stem.spray-baking-powder-powdery-mildew
  5. Reapply every 3-4 days until plant shows no more signs of Powdery Mildew.

Due to the high alkalinity of the Baking Powder (Sodium Bicarbonate or Bicarb Soda), the powdery mildew will effectively not have a suitable, slightly acidic environment in which it normally grows in. By removing this capability, you are ensuring that the leaf material has a coating of natural powder, which by way of application, covers the powdery mildew more so due to the fungal spores collecting the water. When the water evaporates, you have a slight coating of Bicarb on top of the fungal spores.

Important, if you are planning on spraying sensitive plants such as ferns and other house plants, trial the mix first to see if the plant leaf material is affected.

Happy Growing!



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