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Powdery Mildew

What is powdery Mildew?

It’s a group of fungal diseases which looks like a greyish/white powder sometimes in spots or blotches and it can appear on both sides of the leaves of a plant. If it isn’t treated the plants could die, and if crops they may be inedible.

How does a plant get it?

Powdery mildews are prevalent in warm, dry climates, mainly because the fungus does not need water on the leaf surface the leaf surface to get infected. Having said this the relative humidity of the air does need to be high for spore germination, so it is common in crowded plantings where air circulation is poor and in damp. Incidence of infection increases as relative humidity rises to 90 percent and young, succulent growth usually is more likely to be affected than older plant parts of the plant.

Powdery Mildew Fungi on Pumpkin Leaves

What  plants does it affect?

A wide range of plants; particularly damaging to African violet, begonia, rose, lilac, zinnia, phlox, bean, cucumber, squash, grape, and various fruits can be prone to powdery mildew.

  • Plant resistant plants if you can get your hands on them
  • Ensure good air circulation around susceptible plants by spacing plants and pruning out dense growth
  • Clean up and remove plant debris at the end of the growing season to remove overwintering sites for fungi

What can be done about it?

You can spray with a systemic fungicide if plants are vulnerable either because of their variety or situation.

Organic Options

  • Prune out any affected areas and get rid of them straight away, so the spores don’t spread
  • Liberal mulching in the spring to conserves moisture around the roots
  • Spray a solution of baking soda (1 teaspoon per 1 liter water)
  • Spray with Neem Oil