[NAFEX] Apple - Alkaline Water - Powdery Mildew

Stephen Sadler Docshiva at Docshiva.org
Fri Jun 10 19:04:57 EDT 2005


Tom,

A lot of lore about powdery mildew indicates that unlike other fungi, it
appreciates a somewhat acidic, dry, and cool environment.  Your alkaline
water shoulda killed it.  Do you just see curling or do you see the mildew?
In untreated sensitive cultivars the mildew usually exists on the plant,
invisible to the naked eye.  It's benign until it 'blooms' - has a spurt of
growth and spore production.  The keys to getting a fungus to bloom are
pretty mysterious.  Other organisms and minerals are probably involved.  I
remember a patch of lawn that was barren of fungi until someone parked an
old pickup truck on it.  Rusty rain dripped from the front bumper, and a
line of Chanterelles popped up.  There wasn't enough change in moisture and
shade, I wouldn't think, to have caused the bloom; more likely iron or
chromium acting as a biological catalyst.  So maybe something else in your
splashes of water triggered the mildew into action.  Calcium is not shown to
be favorable to powdery mildew.  

Another possibility is that the environment on your apple leaves was acidic,
due to some bacteria or a low pH treatment, and the CaOH made raised the pH
to something more inviting to the pm.  

Powdery mildew treatments aim to change the narrow pH range researchers
suppose it likes.  Treatments push pH down (sulfur, vinegar);
up(hydroxides), or toward the middle (bicarbonates).  A classic organic
spray is a 10% milk spray, calcium and all.  There are also many recipes
that use baking soda and a wetting agent.  

Stephen Sadler, Ph.D.
USDA 9, AHS heat zone 8, 
Sacramento CA - Mediterranean climate

-----Original Message-----
From: nafex-bounces at lists.ibiblio.org
[mailto:nafex-bounces at lists.ibiblio.org] On Behalf Of Thomas Olenio
Sent: Friday, June 10, 2005 2:34 PM
To: North American Fruit Explorers
Subject: [NAFEX] Apple - Alakaline Water - Powdery Mildew


Hello All,

Is there any connection between very alkaline water (dissolved calcium)  
and powdery mildew (PM) in PM sensitive apple culitvars?

I have an odd observation...

We are in the midst of a heat wave in SW Ontario.  The village water is  
very hard, loaded with calcium.

When I watered the lawn, for it was burning out, the hard water hit the  
leaves of the apple tree.  Now the leaves of the tree are showing classic  
PM, curling lengthwise.  This apple cultavar is sensitive to PM.

Would alkaline water accelerate PM?  This may be my problem if the link  
exists.

Any expert input?

Thanks,
Tom
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