It's got to be a Rugosa Hybrid. Some hybrids are prone to PM and/or BS. Rosa rugosa 'Alba' and 'Rubra' are as close as you can get to complete immunity from disease in a rose (...well, I guess KO's and a tiny selection of others can be included) and do not do well at all if sprayed with either chemical or organic sprays. My Theresa Bugnets get PM and my Roseraie de L'Hays get a small amount of BS. They are hybrids. My Rosa rugosa 'Alba' and 'Rubra' never get either. What type of Rugosa do you have? I highly doubt that it is the species rose. While where you live can have a bearing on a roses's disease & insect resistance, I really doubt this is the case with Rosa rugosa, sp. There are lots of Rugosa hybrids available with varying degrees of disease resistance. NE Kansas is very hot and humid, yet my species rugosas are 100% perfectly fine, unlike my hybrids. Try not to be so hard on that other poster.

I have about 80 rugosas and none has one single leaf with a problem. That's why in my garden the rugosas are 80 whereas the hybrid teas are 2.
I love them, they live totally on their own as I am often away and come back just in the weekend, or every second weekend, and I have no time during the WE to do anything but resting. They do not need any attention, I live in a rainy area and they do not need even watering. What could I ask more ?!

Some rugosa hybrids are prone to mildew (e.g. robusta by kordes, not robust at all very deceiving name!).
Other rugosa hybrids are prone to mildew just in the autumn (e.g. sarah van fleet).
Simply GET RID OF THOSE miserable low-qality hybrids! Stay on the good hybrids, and on the botanical rugosas (Alba and Rubra).

Good rugosas are Alba, Rubra, Scabrosa, Roseraie de l'hay and Foxy . They are the most indistructible always healthy thriving plants I have ever seen.

Even my mother was unable to kill these, and if you knew her you would understand that's truly an achievement :lol

My Purple Pavement behaves as well as my Roseraie de l'Hay but is a smaller rose, which is an advantage for me.

Masha

It's got to be a Rugosa Hybrid. Some hybrids are prone to PM and/or BS

*** Actually, I have seen R. rugosa rubra mildew here, near the SoCal coast.
Having already experienced a couple of record-setting heatwaves in 2009, we are now having a strong dose of our once-normal coastal fog. "June Gloom" has set in with a vengeance, and the fog is even reaching inland a fair distance.

In these weather conditions, anything that CAN mildew, WILL mildew. Including species rugosas.
One thing to consider is that much of Southern California has alkaline soil and water -- so rugosas aren't real happy here to begin with. Add "June Gloom," and you're asking for trouble.

Our last rugosa will be leaving here as soon as DH has time to shovel it.
Like the little girl with the curl in "the middle of her forhead," Where rugosas are good, they are very very good.
But where they are bad, they are horrid.
They're not the best choice for Southern California gardens, unless you want to make gardening harder than it has to be.

Jeri

Roseraie de L'Hay does get a small degree of BS for me unfortunately. I got rid of my Teresa Bugnet. They were covered in powdery mildrew no matter what I did, but my Rosa rugosa 'Alba' and 'Rubra' never get anything. I forgot to mention Jens Munk. It's been disease free for me, too. Great roses!!! We have alkaline soil (lime & clay) & alkaline water here in KS like CA, so that's not necessarily the problem and we get temps in the 90's often in the summer and sometimes over 100.

and we get temps in the 90's often in the summer and sometimes over 100.

*** We (God be thanked) DO NOT.

Our coastal climate is still cooler and more humid than anyplace 10 miles further inland.
Until very recently, homes here have not had air conditioning -- and those who DO have it, rarely use it.
MANY roses mildew here. Many rust. Blackspot is STILL very rare.

Jeri

Since there are thousands of roses that resist powdery mildew, the original poster really ought to get rid of the plant.

Someone mentioned the hybrid rugosa 'Robusta' getting mildew; I once saw this rose with the nastiest-looking blackspot I've ever seen. The leaves were so covered with dark crud that there was hardly any green showing.

jerijen I'm just saying that soil & water pH may not be the problem, it might be the type of rugosa that she has. I was commenting about the heat only because of what you said you had experienced recently. I love many things about KS, but the heat plus humidity in summer is not one of them. Not having to use A/C sounds wonderful. I think michaelg is right. Get rid of the plant. There are others (other rugosa hybrids or other types of roses) that should do much better for her. Wal-Mart isn't the best of places to get roses. As you found out bug_girl deals are not necessarily all they're cracked up to be. So what kind of rugosa did you buy or did it just say 'Rugosa' and you don't really know exactly what it is? We're all here trying to help. Spraying it might not be doing it any good either. Rugosa don't do well with spraying. Shovel pruning the rose is a good suggestion. I'd listen especially to the advice given by those who live in CA.

In web surfing, I've read about many in CA that have had difficulties in growing any Rugosas which confirms all that jerijen has been saying. Maybe those in CA can suggest better roses to try in your area. I have plants that I'd love to grow in my yard, but have had to accept that I'm not living in the right area for them. We all have that problem. Still keep in mind that not all Rugosas are created equal.

We get 90 degree heat here, too, but we also have real winters. It may be that rugosas need a cold winter. I've never had a sick rugosa, neither here nor in Santa Fe and I've only lost two, Hunter and Moje, both bands, both hybrids and both because I stuck them in out of the way places during my busy season and forgot to water them.

Oh, I'd shovel-prune the thing in a heartbeat, if it were mine.
Rugosas just aren't an optimal choice for this area.

There are roses than can grow in Southern California completely spray-free and carefree.
They're just not the ones you read about in most of the books.
And you won't find 'em at Wally World.
:-)

Jeri

I think I may have to get rid of it. I don't like spraying it every week, with the canned spray and I can put it something better. I am worried about cancer for myself, and it does not seem worth the cost even of the weekly dose of canned spray. I have had good luck with John Keats. It does not get fungal in San Francisco, but needs the occasional spray still. I don't like to spray more then every 6 weeks. The cost of the cans at 10 dollars a can, and it won't take you very far, will exceed the price of the plant quickly. So, I missed one week of spraying now it's got power mildew again, on each leaf. It's a mildew factory.

Hi Bug girl, long time no see!

Do you have any pictures of it?

have you tried cinnamon? google organic gardening tips for roses

I too live in coastal Southern California, and by serendipity (the 99 cents store a few years ago), I ended up planting the white J & P rugosa hybrid "Wild Spice" -- which has the nice rugosa limey green quilty-fuzzy foliage. I can report now that it does not mildew in my coastal canyon (where almost everything mildews, even with spraying).

The flowers are short lived -- one day max if it's warm, but I like the plant specifically for the foliage, which is very different from any other rose in my garden.

I did discover early on that rugosa foliage REALLY resents spraying. If it even gets touched by the Banner Maxx or Compass or Funginex type sprays I regularly use on my other roses, those leaves turn brown and fall off. So this rose gets no spray at all, and I've never once seen any mildew or rust on it.

Kathy