Powdery Mildew

Powdery Mildew
  • Powdery mildew is a fungal disease affecting a wide range of plants.  It's caused by various fungi in the order Erysiphales.   Risk of infestation are greatest when the weather starts to warm in spring and humidity is high.
  • It has been a regular visitor to my garden over the years infecting strawberries, peas, cucumbers, beans and pumpkin.  Affected plants are easily identified since they develop white powdery spots on their leaves and stems.  These spots grow rapidly until the plant's foliage shrivels and eventually dies.
Details
  • Binomial name                         Blumeria Graminis.
  • Family:                                    Erysiphaceae. 
Why Powdery Mildew is a Pest.
  • If allowed to grow unchecked, powdery mildew will cover a crop, reduce its capacity to photosynthesise, seriously reduce yields and eventually kill the plants.  It will spread from plant to plant very quickly given favourable conditions.
Pest Control. 
  • Aerated compost tea used as a monthly foliar spray toughens plant foliage and provides protection against powdery mildew infestation.  However, new growth emerging between scheduled sprays is vulnerable, and spraying foliage already infested with aerated compost tea will not kill the fungi.
  • Stronger measures are needed, and at the first sign of an infestation of powdery mildew, I use an organic fungicide to stop it spreading.  I have found this to be very effective, but it will not protect the plant for long and successive spraying every few days or when the mildew reappears may be necessary.   A 10% solution of cow’s milk in water can be used as a homemade alternative.