http://www.rose.org/rose-care-articles/downy-mildew/

Here is a good article on downy mildew, which normally starts at the top of the plant and works its way down. It needs ideal conditions to germinate--around 68 degrees and very high humidity--over 85 percent. More likely in the cool days of fall rather than the wacky weather days of spring.

I do not know what it is but mine have it also. Horrible spring weather. Very little sun, too many drippy days and cold.

I did receive downey mildew thru the mail this year. This was the first time I had ever seen it. The box and I ran for cover after opening. Here is the best that I can say. Downey mildew does not cross main veins. It will travel in-between them. Then something I never knew before was to turn the leaves over. Then look for the sparsa spores. If it is downey mildew it will be there. On the underside of the leaf below the downey patches there will be white patches of spores. They can be hard to see so I used a magnifying glass. They look like tiny little white dots in patches. Yes my new rose had downey mildew.

My leaves that look like yours do not have the sparsa on the back. Now is the perfect weather for black spot and anthracnose and my roses are now getting both. I've been no spray for quite a few years now and only purchase the healthiest of roses. Will sad to say that does not mean that they won't get anthracnose. I did learn last year that if I did nothing it was very hard on the roses. Maybe since conditions stayed good for anthracnose nearly all of last year. In order to get things under control I have already sprayed this season with Bayer disease control (not 3 in one). Good luck in your quest to keep your roses healthy. I'll report back if I have any luck.

I do not know what it is but mine have it also. Horrible spring weather. Very little sun, too many drippy days and cold.

I did receive downey mildew thru the mail this year. This was the first time I had ever seen it. The box and I ran for cover after opening. Here is the best that I can say. Downey mildew does not cross main veins. It will travel in-between them. Then something I never knew before was to turn the leaves over. Then look for the sparsa spores. If it is downey mildew it will be there. On the underside of the leaf below the downey patches there will be white patches of spores. They can be hard to see so I used a magnifying glass. They look like tiny little white dots in patches. Yes my new rose had downey mildew.

My leaves that look like yours do not have the sparsa on the back. Now is the perfect weather for black spot and anthracnose and my roses are now getting both. I've been no spray for quite a few years now and only purchase the healthiest of roses. Will sad to say that does not mean that they won't get anthracnose. I did learn last year that if I did nothing it was very hard on the roses. Maybe since conditions stayed good for anthracnose nearly all of last year. In order to get things under control I have already sprayed this season with Bayer disease control (not 3 in one). Good luck in your quest to keep your roses healthy. I'll report back if I have any luck.

I'm afraid if I delete this 2nd comment that both will disappear so I'll leave it.

Thanks Patty! This was so helpful! I checked the leaves and there is nothing underneath. Thanks for the tip. I know how the typical downy looks like (mosaic like) but then you find such conflicting images online. I would be devastated as my roses are still so young. I spray mine. Usually with Bayer fungicide but this time I used Bayer 3 in one for the first time. Everyone is raving about it so I figured I try. Best of luck to you too. Let's hope it warms up soon.

3 in one. A brave acknowledgement.

I wonder if it's from our crazy temperature swings?

M Z, Bayer 3 in 1 (combination products are not recommended, BTW. not enough fungicide, fertilizer, or insecticide to be effective, and takes too long to be absorbed by the plants) won't help with downy mildew if that's what you have.