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andreark

Bayer every 2 wks, but for how long?

andreark
10 years ago

I live in the delta area of the SFO bay area. I use Bayer Advanced and thought (duh!) that I could stop spraying a couple of weeks ago....NO DICE!!! BS is back.
My question is, how long do I keep spraying? Any 'rule of thumb' for northern cal?

andrea

Comments (13)

  • Maude80
    10 years ago

    I'm not in your zone but I do use Bayer and I spray until november usually.

    Maude

  • buford
    10 years ago

    You should continue spraying until you have a hard frost, if you want to keep your roses clean. You will not have to spray every 2 weeks.

  • andreark
    Original Author
    10 years ago

    If you mean 32 degrees, we hardly ever get that cold.

    Thanks anyway,

    andrea

  • susan4952
    10 years ago

    In Chicago, the disease pressure is very high in the fall. I spray until the leaves start to fall off with dormancy, wind, etc., or until I get sick of it.

  • roseseek
    10 years ago

    I wouldn't think you should have black spot issues in temperatures lower than about seventy degrees, Andrea. You'll have to check your micro climate to see when that should be. It's entirely possible for hard scape, walls, etc. to radiate enough heat to raise the temps enough to trigger an out break even when the forecast is for lower temps. It should really be "when conditions promote the disease" rather than any specific date. Nature doesn't wear a watch nor look at any calendars, as we've all seen from our weird weather. Kim

  • buford
    10 years ago

    I get a lot of anthracnose in the fall. It's not just black spot you have to worry about. Sometimes we don't get a hard frost until December. You don't have to spray. I'd stop when the leaves start falling off, if they do. You are going to do spring pruning and remove all of the leaves anyway.

  • andreark
    Original Author
    10 years ago

    Thanks all.

    And Kim, that makes great sense. I just looked at our averages, and it looks like it won't drop and stay below 70 until about Nov. I will just plan on spraying until then, unless of course we have an unusually cool autumn.

    I have been tracking something with my HTs, and will let you all know the outcome in a month or so. It's very interesting so far. And I hope the conclusion is as it looks to be now....

    My new English roses and miniatures are going wild. They look great!

    Hugs for all,

    andrea

  • michaelg
    10 years ago

    We need to hear from more folks in the Bay Area and PNW. My understanding is that most who spray in that region do not continue to spray for blackspot through the summer dry period.

    To germinate, blackspot requires rain or something else that keeps the leaves wet continuously for 8-12 hours at temperatures continuously in the 60s and 70s. If you do not have those conditions, you will not have spread of blackspot.

    Dark spots of cercospora fungus can persist for a couple of months and come to your notice only when they finally start killing the leaves Or, conditions for blackspot can occur occasionally and produce a few spotted leaves. That does not mean the disease is going to do a lot of damage.

    Be careful not to wet the leaves in the evening.

    In the East, we have conditons for blackspot throughout the growing season. In other areas, it may be too dry or too hot for part or all of the year.

  • andreark
    Original Author
    10 years ago

    Michael, thanks for your response..

    We are in the dry season. But my roses get lightly sprayed by my lawn sprinklers. I didn't spray at first because I didn't realize that they were getting wet in the evening. When I asked a Rosarian from Regan's Nursery what was wrong, she said "are your lawn sprinklers on in the evening?" I didn't realize that they were also getting my roses. So I changed the timing for them to the morning. (I had already sprayed a couple of times.) Then, I thought that I would have no more problem with the leaves. But after a month, I noticed that the leaves were still turning yellow with black. So I started again. I have been removing all infected leaves before I spray, thinking that if any more turned yellow, I would know that the spray wasn't working, OR, I wasn't doing it correctly, OR , there was something else going on. I use Bayer's Advanced Disease Control.

    Well, they are still turning yellow and black. Not enough to defoliate the plants, but why are they doing this at all?

    andrea

  • michaelg
    10 years ago

    Could we get a really sharp picture of a spotted leaf?

  • andreark
    Original Author
    10 years ago

    I just sprayed (and deleafed) yesterday. If I get a photo in the next couple of days and post it on this thread, will you see it?

    andrea

  • michaelg
    10 years ago

    Sure, I'm a forum junkie.

  • andreark
    Original Author
    10 years ago

    Thanks, will do.

    andrea

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