Downy Mildew on Roses

Forum Archives

 

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Fern

Location: Washington, Western Cascade Foothills

Posted: Jun-02-2005 at 7:45am

I've seen alot of downy mildew on roses in the Puget Sound area this year. I might have had some before but thought it was just black spot disease. I've been trying to find out about it and realize we've had the perfect conditions for it. It is a systemic disease and it seems like it is probably already in the roses when I buy them because it is already in the major growers area [ Wasco Count, CA]. I haven't bought any new roses in two years. I also read it is in wild blackberry plants. Does anyone know more about it? Has it really always been around but only this year the conditions were just right for it? Is it yet another disease that will cause problems alot of years? I love roses but I don't spray. I don't mind ugly leaves as long as it flowers. I only grow mildew and blackspot disease resistant [but I know it doesn't mean disease proof]roses but I hear it maybe different ones for downy mildew. If I was to spray I would use Serenade, a new organic fungcide that is a bacteria that attacks fungus. You're supposed to spray it every 7-10 days but I was wondering, if you sprayed it once wouldn't you be inoculating it in to your yard and it would reproduce itself? I have lots of fungus diseases it could eat!

Fern

 

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Screaming Eagle

Location: Puget Sound corridor

Posted: Jun-02-2005 at 9:04am

I noticed that this year my normally very resistant rose has black spot, YIKES! And just when I thought it was safe to back into growing roses again! I'll be eager for any great organic tips out there to nip this little problem in the bud. I've been practicing good hygeine under my rose, keeping the dead leaves and such picked up and out of the compost pile.

By the way Fern, what does downy mildew look like? I'm guessing it's like it's name: white and fuzzy?

TIA,

Theresa

 

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Fern

Location: Washington, Western Cascade Foothills

Posted: Jun-02-2005 at 9:39am

I should explain downy mildew because it fooled me and I thought it was black spot. You can have both on the same plant. The difference is that you see some small brown spots even on the newer leaves and the brown spots are a little purplish and have an entire margin instead of the fuzzy edge of black spot. It also looks like chemical burn sometimes. They both cause yellowing older leaves with black spots on them. I also want to say I will never stop growing roses because some of them really are low maintaince blooming machines. You just have to pick the right varieties and not expect perfection. I'm slowly trying to put together a list of truly hardy and almost disease proof roses that people have personally grown for this area. When I get time I will post the list so far and I would love to have other people's input.

Here are some links to pictures of downy mildew. http://plantdisease.typepad.com/plant_disease/2005/03/tpddlrose_downy.html http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=985

Fern

 

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cjmiller

Location: Oregon, Willamette Valley

Posted: Jun-02-2005 at 10:26am

Downy Mildew: Isn't the name deceptive? It sounds so warm and cuddly.

I have slowly switched from patented roses to hardy herloom roses, but some still get rose leaf diseases. Frustrating. Thanks for the links, that is helpful, Fern My main source of comfort is that when a plant gets sick and dies, it means you have room for a new plant! Now, that's my kind of illness.

Carol

 

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Fern

Location: Washington, Western Cascade Foothills

Posted: Jun-02-2005 at 9:07pm

I think the heirloom roses are great too, I love their old rose scent and grow a couple of them. My problem is I'm atracted to the peaches, arpicots, oranges and yellows that the heirlooms don't have. Those are usaully the least hardy ones and most prone to disease too.

Fern

 

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cjmiller

Location: Oregon, Willamette Valley

Posted: Jun-04-2005 at 4:55pm

Have you been to Heritage Old Garden Roses in St. Paul, OR., or even get their catalogue? I have a soft apricot herloom named Sweet Juliette, that has a marvelous aroma and I love the shape of the rose. It blooms heavily now and later in the summer. You might want to take a look at what they have to offer.

They have a website, look up at Heritage Old Garden Roses. St Paul, Oregon.

Carol

 

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hollysue

Location: Washington, Southwestern

Posted: Jun-04-2005 at 5:45pm

I think you might mean Heirloom Roses in St. Paul, OR. Fabulous gardens there, and the quality is wonderful!!!

If you have a garden and a library, you have everything you need.

 

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sunpath8

Location: Western Washington

Posted: Jun-14-2005 at 12:28pm

I think that my rose (peachy and less disease resistant as you mentioned) has this exact problem. I didn't have any problems with the plant last year and suddenly it isn't doing so well. I have to agree with CJ (because it was the first thought that came to mind) that if this one dies it just makes room for a new plant

 

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Fern

Location: Washington, Western Cascade Foothills

Posted: Jun-14-2005 at 8:26pm

After talking to people I've come to the conculsion that downy mildew has always around here but isn't much of a problem. It wants tempatures in the 70's and raining. It might have started right after those 3 warm days we had a couple of weeks ago. It's cooler than it likes now and my roses aren't getting much worse. Of course backspot supposably likes it warmer too. New strains of backspot are evolving all the time and I bet we have one that is adapting to cooler weather! Some of the new varieties of roses are turning out to be very disease resistant, I'm glad the breeders are taking it seriously. Fragrance, too.

Fern

 

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Fern

Location: Washington, Western Cascade Foothills

Posted: Jun-15-2005 at 8:55pm

We got a letter [or fax, I forget] at the nursery yesterday from the sales rep of Jackson and Perkins saying he had gotten alot of reports of blackspot and he had checked them out and it was not blackspot but downy mildew. They recommended spraying with all the usual disclaimers. A little late because most fungicides are only preventive. Good thing our rose person at nursery recognized it two weeks ago and we [ really not me, I did customer service and I am glad because it was a painful, hard job] pulled the bad ones, cleaned, and spaced them. Someone sprayed with daconil afterwards.

We are selling alot of Serenade, the new organic fungicide that is supposed to work. I hope it does, neen oil didn't turn out to be very effective on the fungus diseases.

Fern

 

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KrazyKarma

Location: Washington, Puget Sound Corridor

Posted: Jul-05-2005 at 7:20pm

There is a product out there called Neemazal. It's a concentrated oil made from the kernal. The chemical in it is called azadirachtin. Maybe this will help?

Playing in the dirt is good for the soul!

 

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Lisa A

Location: Oregon, Greater Portland Metro

Posted: Jul-05-2005 at 9:59pm

Hi KrazyKarma, welcome to Rainy Side! I like your signature line.

From what I can determine from this website, Neemazal is a broad spectrum botanical insecticide. Even though it is a broad spectrum botanical insecticide, according to this website, Neemazal doesn't affect bees and is gentle on beneficials, contrary to other broad spectrum insecticides. However, it is not a recommended treatment for fungal problems such as downy mildew.

It is always best to determine what the problem is and to choose a product or action that specifically targets the problem. If you choose to use a product, botanical or synthetic, always, always, always read the label and use it according to the instructions for your health and safety as well as for the benefit of your garden and anyone who visits your garden. (yes, this has been said many times, but it is worth repeating.)