Documents: Latest From: The Real Dirt:

Powdery Mildew
by Jerry Filipski
by Jerry Filipski


Gerald (Jerry) Filipski is the gardening columnist for the Edmonton Journal, a position he has enjoyed as a freelance writer for the past 12 years. Jerry also writes for Canadian Gardening, the new Alberta Gardener as well as for the lifestyle magazine of P&O ferries. Jerry also does numerous public speaking engagements including some major gardening conferences and workshops as well as question and answer sessions for Wal-Mart and Rona.

June 7, 2009

Many home garden plants can be affected by powdery mildew. If your plant’s once-attractive green leaves have a white or greyish coating on them, mildew is likely to blame. Powdery mildew is a fungal disease brought on by environmental factors. The disease shows ups around mid to late season, when growing conditions best allow the disease to spread. Spores produced on infected plants and carried by air currents spread the fungus to new plants.

The spores are most troublesome when conditions are humid, and the hot humid days and warm nights of the late part of summer are ideal for the disease to take hold. The disease is also more prevalent when the seasons are wet. Plants grown in shady or overcrowded conditions are more likely to host the disease. Mildew is not usually fatal to plants but it can affect flower and fruit production as well as the plant’s general appearance.

You can control powdery mildew by:

• Choosing mildew resistant plant varieties.

• Ensuring the plants aren’t crowded. This will allow good air circulation.

• Limiting the application of nitrogenbased fertilizers so plants grow more slowly.

• Watering plants susceptible to powdery mildew at the soil level, not on the leaves.

• Burning or otherwise disposing of affected foliage in the fall. Do not compost as the fungus can overwinter in the compost.

An alternative to cultural control is chemical. Garden sulphur sprays are effective in controlling the disease. Neem oil has also been proven effective. Sulphur and neem oil are natural products and thus deemed eco-friendly choices. (Milk heavily diluted with water can also be effective, as is a teaspoon of soda and half-teaspoon of dish detergent in a liter of water.)

This article first appeared on Vist to subscribe to their great garden magazines!

  • New Eden
  • Kids Garden
  • Plant a Row Grow a Row