Powdery Mildew in the Garden

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Powdery mildew is probably the easiest to recognize of all plant
diseases in the garden. It is a fungal disease that attacks just about
every plant in your garden. A wide variety of fungi cause powdery
mildew on different plants, but it is recognized by the appearance of a
white or gray coating on the surface of the leaf or stem. It looks like
someone sprinkled baking flour or baking soda on your plants or like
your garden is covered in dust.

Vegetables, shrubs, herbs, annuals and perennials are susceptible to
the disease. Symptoms of powdery mildew usually appear late in the
growing season during periods of high relative humidity. Besides
looking unattractive, the fungus can cause stunting and distortion of
the leaves or growing tips/buds, and generally weaken your plants.

my garden the Zinnias and sunflowers are usually the first to show
signs of powdery mildew. After all the recent rain we’ve had I’ve been
expecting them to fall victim to the disease, but they’ve remained
powdery mildew free. Instead, the weeds that I let get out of hand have
been the plants falling victim in the garden. One of the reasons for
this is that powdery mildew thrives when plants are crowded and planted
to close to each other and air doesn’t circulate well in the garden. So
the weeds near the foundation, under and around the front stoop got it.

So, how do you deal with powdery mildew in the garden?

I’d usually just pull the plants affected because it normally attacks
the annuals that I grow from seed. I find pulling these annuals a lot cheaper than letting it spread and infect the perennials which
cost more money. You can pick up commercial fungicides at the local
garden center or nursery, but remember they vary and not all fungicides
will work on all plants. Make sure the fungicide you purchase is for
the plants you intend to spray and follow the directions. The fungi
that infected your roses is different than the fungi that infected your
lilacs, lawn or cucumbers. You should also know that fungal organisms in the
garden can’t be “cured,” once you’ve noticed them, the way to deal with
them is to prevent the development and spread. Spraying plants with a
fungicide will prevent new growth from being infected with powdery and
keep it from spreading in the garden.

I’ve blogged about the
garden hose being eliminated and I think not
having a hose and sprinkler has been what’s saved my plants this year. A number
of plants were pulled because they were not happy without regular
watering. This helped “fix” one of my newbie gardening mistakes of
trying to grow too many plants in a small space. Less plants means more
air circulating and more sunlight reaching plants in the garden. The
loss of the sprinkler meant that plants didn’t get watered from above because
I have to make sure plants got watered at their base.

up and dispose of dead leaves, twigs and branches in your garden. This
is particularly important because spores can be carried to healthy
plants, by water, bugs and wind.

Have you tried one of those home remedies for fighting powdery mildew? If you have and there’s a recipe in your chemical free gardening arsenal feel free to leave a comment about it below.


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  • I have it on my zucchini leaves and I do nothing. It's late enough in the season and the zucchinis themselves are still growing OK... and the only things near them are maters which aren't susceptible. I don't compost those leaves, though.

  • In reply to gardenfaerie:

    I'm keeping my fingers crossed that my Zinnias I sowed late July will be ok. They just started blooming for me.

  • In reply to gardenfaerie:

    Now, I've been told, and - I haven't tried this YET but I want to - I've been TOLD that spraying milk on plants will prevent powdery mildew. Just any kind of milk from the grocery store. However, I don't know if this is due to natural components of the milk or the antibiotics given to the cows that happens to be in the milk. If that's the case, then it's not so "organic" but, if it's a natural element of the milk then - perhaps it's a good fix! I'd love to try this out, I just haven't been able to yet!

  • In reply to bfuta:

    Hi Ben,

    I think it is suppose to be a mixture of 50/50 water and milk. Something about the anti-fungal properties of milk. Though, like you I haven't tried it, milk is too expensive to spray on plants. :0)

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