One of the most common problems this last growing season was Powdery Mildew! We had quite the wet growing season in 2006 making it difficult for many of our favourite plants to thrive.
Throughout the latter part of the season I watched as one by one my vegetable plants withered away due to either powdery mildew or some other fungus.
The main cause:
One of the main causes of powdery mildew is over-watering. Leaves on either trees, shrubs or perennials remain wet for long periods of time. Usually plants that exhibit powdery mildew the most will have poor air circulation around their branch structure. There is a tendency for the leaves to trap humidity in the air and cause the perfect growing environment for the airborne fungi spores to fester and spread. Suddenly the leaves develop this white haze look to them.... you've got powdery mildew!
Earlier this fall, my Uncle down in Florida asked me what to do for powdery mildew growing on his Zucchini plants. He is into organic gardening...in one of the toughest environments to avoid chemicals...Florida! As he calls it, the land of pestilence! Everything is fair game in the garden.... Anyway, in my researching, I found someone that discovered spraying milk on plants killed powdery mildew!
He also described using powdered milk (15 grams) to 1 liter of water... the powdered milk kept the smell of old sour milk down once you applied it as a foilar spray. Get Milk info !!!
So if powdery mildew has had it's way with your garden, consider an organic solution rather then a chemical attack. It's the enzymes in milk that attack the powdery mildew and break it down so that it does not function.
Some of the most common plants that exhibit powdery mildew in Ontario; Phlox, Tomato vines, Zucchini plants, Roses, Azaleas, Dogwoods and most popular....the ever invasive Norway Maples. (and yes, Poplar trees as well in case your wondering if I made a spelling error....though they are not popular landscape trees)