Bob Moore asked:
> Does anyone know of any informaiton on controlling powdery mildew
> on vegetable plants.
Am I remembering correctly that there are different types of fungi
loosely called powdery mildew (Sphaerotheca on fruit, Leveillula and
Oidiopsis and Podosphaera on vegies, Erysiphe on grains and sometimes
vegie crops) that affect different crops?
I don't know how important that is in determining control, but
here's a few things I have bookmarked Web-wise or heard of or
The Pacific Agri-Food Research Center in BC reports the use of
100 ppm soluble silicon in nutrient feed (in the form of potassium or
sodium silicate) as a control for powdery mildew (hereafter PM) in
Somebody there might be able to answer whether this has been shown to
be effective with other cucurbits.
Oregon State University's botany department offers general cultural
control recommendations in wheat which sound like they'd apply to
vegies as well: avoid excessive N fertilization; allow for adequate
air circulation in plant stands; and use resistant varieties.
In the world of small grains I've heard people recommend eliminating
crop residue, rotating crops, and not allowing volunteers
(potentially inoculated) as cultural control methods for PM. I'd
think this would be the same for vegies.
I've had good results in growing vegies myself with these
practices--PM is a major problem in the hot humid Wisconsin summers,
particularly since my gardens get planted Tokyo Subway style. That
means about five times as snugly as French Intensive. I've never had
the luxury of more than 1,000 square feet of soil to grow food on.
I've always used a garden weasel to keep soil loose and disturbed
around plants, and also to make music for the earthworms.
In the years where I was gardening while enduring serious chronic
pain, I had fairly wide, straw-mulched paths so I could recline
while working. When the straw was spory, my plants had more problems.
So I found myself less willing to regard "spoiled hay" or old marsh
hay as an "economical" source of mulch.
Some organic vintners and pome-fruit farmers of my acquaintance in
Penna. and Calif. apply sulfur to control PM.
There are a lot of chemical control recommendations--Banner,
etc.--that you can get thru any traditional Extension source. Here's
a typical fact sheet:
I.e.--AhOOOga, ahOOga! The disease has been observed in the state of
Michigan! Spray now!
IPM recommendations for various crops are available at the UC-Davis
You have to search by crop, then look for PM under that. Some of the
crops/pests have organic and cultural control information.
One last thought--I remembered hearing that PM likes DRY leaves, not
wet leaves, and humid conditions. So I did a quick search and turned
up this information from U of GA.
The plant pathologist writes: "Powdery mildew infection peaks under
warm day and cool night conditions (typically, 81 F daytime
temperatures with 40-70% relative humidity and nighttime temperatures
of 61 F with 95-99% relative humidity). Unlike other foliar fungal
diseases which are normally favored by wet leaf surfaces, powdery
mildew is favored by dry conditions. In fact, powdery mildew spore
germination is inhibited by moisture on leaves.... Since the disease
is favored by high humidity and poor air circulation, increase plant
spacing, avoid watering late in the day which can increase humidity
levels and reduce humidity by increasing air circulation and venting
the greenhouse late in the day to exchange warm, wet air with drier
air from the outside to reduce infection." She then goes on to
Hope this helps. All hail cucurbits, the Space Pods of the vegie
world!!! This time of year I like to sit near them and watch and
listen to them. All that hope for the future, encapsulated in such
funky, functional packages. Don't you just adore them?
Michele Gale-Sinex, communications manager
Center for Integrated Ag Systems
UW-Madison College of Ag and Life Sciences
Voice: (608) 262-8018 FAX: (608) 265-3020
The black sesame rice crackers weren't sealed well,
so they're the slightest bit soggy. They stick to my
teeth like tamari Captain Crunch. --Mister 3D
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