[Arid_gardener] Re: Powdery Mildew on Roses

[Steve Sheard]

Dear "Hate Chemicals",
  I am a consulting Rosarian with the American Rose Society. May I offer my input.
  Control depends what is concidered acceptable.
   
  I have about 150 rose bushes and maybe 20 had some level of Powdery Mildew (PM). 
   
  Some Rose varieties are more suceptable than others.
   
  PM like the cold damp nights with little air circulation.
   
  Water at sun rise so that the plants are relatively dry by the next evening. 
   
  This year I did not use any of the Traditional Fungicides and I felt I had acceptable control. You could see some signs on the leaves but no major "fur".
  I washed off the PM in the early morning once a week with a VERY strong water spray. 
  I then sprayed the bushes once every two weeks with "Green Cure" - A Potassium Carbonate base control.
   
  Now the days are over 100 and the nights in high 60 - the PM has gone - until November.
   
  For more information visit our Rose Society web site. http://www.roses4az-mevrs.org/
   
  Regards
  Steve Sheard
  Consulting Rosarian
  480 831 2609
   
  

Olin Miller <derGartenArzt at worldnet.att.net> wrote:
  According to http://cals.arizona.edu/pubs/crops/az1033.pdf

"Disease is favored by moderate or high humidity and low light
intensity, conditions which are often prevalent on lower plant parts or
in thick foliage. Powdery mildew is found throughout the low desert
areas most of the year. At higher elevations, disease appears as host
plants begin to grow or develop new foliage. It is favored by warm
temperatures and is one of the few foliar diseases that is prevalent in
the desert areas."

According to http://cals.arizona.edu/pubs/garden/az1306.pdf

"It is a seasonal problem that thrives with cool, damp nights, warm
daytime temperatures in the 70s or above, moderate to high humidity, and
poor air circulation.

Olin Miller
Master Gardener Volunteer, Maricopa County AZ
======================================================

----- Original Message ----- From: 
Sent: Thursday, May 11, 2006 6:21 AM
> What is Powdery Mildew indicative of? Watering schedule off? Soil
> composition off? Sunlight access off? Disease? All of the above?
> I know I can spray my roses with chemicals - tried that (it works!) -
> but
> hate chemicals.


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