Powdery Mildew

Powdery mildew is a common fungal infection causing whitish, powdery spots on the leaves of susceptible plants. And plants susceptible to this group of fungi include melons, cucmbers, squash, pumpkins and roses to name a few.

Pictured here is what powdery mildew looks like; you have probably seen it before... in fact it is one of the oldest recorded plant diseases.

This infection is caused by a variety of different fungi which, on the bad side, is why it is so common. However, on the good side, each fungal type will only affect a specific plant. This means that an infected cucumber will not cross over and infect a squash.

So what causes it? Damp weather with summer temperatures, plants planted too closely together and plants that get a lot of shade all contribute.

And once powdery mildew begins to form it grows really quickly; a full blown infection can occur within 72 hours.

But this fungal infection can be easily treated and without the use of harsh chemicals. These fungi seem to require damp conditions to take hold but, paradoxically, require a dry leaf to grow. And it does not like sunlight.

This is a picture of one of my hydroponics cucumber plants after a devastating bout with powdery mildew. The mildew comes on fast and must be treated early or it will result in extensive damage as shown.

Since the fungus grows so fast I simply did not notice it until too late (it had a full 24 hours to take hold). I did treat it successfully but the damage was done.

The powdery white/gray spots will destroy the leaves and inhibit photosynthesis effectively destroying the plant.

So if you cannot catch this fungus early, your plant's leaves will look like my poor cucumber leaf pictured here...the only cure now is to remove the infected leaves.

Treatment may have to be applied several times a day for a few days but keep with it and you will be successful.

And I cannot stress this enough: before applying any chemical of any kind to your plants, ALWAYS apply it to a small section first to make sure your plant leaves can tolerate it.

The common ingredients effective against powdery mildew described can be mixed with water and strained into a spray bottle and sprayed on your infected plant.

I will mix the ingredients in a container and let sit for a few hours. Then I strain the mixture through cheesecloth into a spray bottle.

Included below are some common recipes that are very effective against the fungi. Mix the ingredients, let sit in the sun, if possible, for about six hours and strain.

The ingredients in the following recipes can serve as a guideline when you devise your own fungicide mixture. Keep in mind that your goal is to either change the ph or directly attack the fungi. Water is a good mixer as well as tea, oil will help the mixture stick to the leaves and will smother the fungi. And soap will also help the mixture stick to the leaves. So feel free to mix and match ingredients.

1/2 cup milk 1/2 cup water	Equal parts of milk and water are very effective.
1/2 teaspoon potassium bicarbonate 1 gallon water	A .5% solution works the best.
1 or 2 teaspoons baking powder 1/2 gallon water	Baking powder contains potassium bicarbonate.
1 teaspoon neem oil 1 pint water	Works well by itself or can be used in combination with other ingredients.
1 tablespoon hydrogen peroxide 1 gallon water	A 2% solution works the best.
3 cloves garlic, chopped 1 pint water	Garlic contains sulfur which powdery mildew does not like.

Good luck!

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