Hi Everyone:

I have three, large, mature rose bushes and it looks one has a disease and might be spreading to the others. They are about 10 years old. They are in the Santa Clarita Valley in north Los Angeles County. They are in full sunlight. It gets hot enough here that we sometimes have sunburn issues. This is something different.
It looks like it is affecting the leaves and the canes.

The Any help/advice is appreciated. I have uploaded images. Please feel free to ask questions.

It looks like sunburn damage. Some of mine have it too, even though I'm at the ocean.
I know it's been very hot lately out where you are. Long Beach is THE hottest beach city in So. Calif. so some roses I have aren't very heat tolerant.
You can avoid "some" of this by providing some sort of movable shade structure to protect them from the hot sun and heat...like umbrellas.
Also, water them heavily in the summer heat. That will help. Water them at the base of the plant and avoid getting the foliage wet as that makes them burn faster.

@deancox ...This is only a guess on my part. Since you said they were mature plants, they have lived through hot summers in the past.

The symptoms you are showing in your photos look to be water stress. I have a hunch something is going on with the roots and they are not providing enough moisture to the top growth.

@Calsurf73, Mike ... I actually spray down all of my roses when the temps hit the triple digits. However, I am inland and do not have the ocean influence and that may make a difference. Roses do absorb moisture through their leaves and my spraying practice controls spider mite infestations. I have not seen any foliage burn up here.

I agree, that is sunburn. They need water and shade until it cools off.

I also agree with Lyn. I give my roses showers on very hot days to cool them off. I swear you can hear them sigh with relief, lol!

YUP.
That looks like sunburn to me, as well.

It's stayed cool along my part of the Ventura County coast, but I know y'all have been heating up in your area. I like Mike's idea of a portable shade. Maybe something of pvc, with shadecloth on it? You won't want to leave it there in windstorms, but in other times, that could be good.

And, like Lyn and Seil, I really like hosing roses off with water on a really hot day. It not only hydrates their environment, but it hampers spider mites.

Hmm, OK Thanks for the input. Is there any truth to the idea that spraying them in the heat of the day will make the water into small prism that actually burn them worse?

These roses are 20+ years old and have lived through much hotter summers than this one without exhibiting this kind of damage. We have actually had a relatively moderate summer with only a couple of weeks into the plus 100"s

@deancox ...

In my experience, the answer to your question is "no". I've heard the same thing about tomato plants. Up here, my summer temps are in the high 90s to low 100s for 2 to 3 months. I've never seen burned foliage due to spraying my roses.

Dean -- Water won't burn your rose foliage.

But that does raise a point . . . Have you used ANY Horticultural Oils? (Neem Oil is so popular.)

Because ANY oil on the leaves burns foliage here in Camarillo, on my South-facing hill, if it gets over about 75 degrees. Dilute compounds of dish detergent have done that, here, as well.

Your question about whether water droplets burn leaves has been answered (it's "NO"), but here's something to think about. Mother Nature doesn't just send rain in the early morning or late evening. IF water droplets on leaves could cause burning, every time it rained and then the sun came out, everything green would soon be everything brown. In just the past two weeks here, there have been multiple afternoon showers where it has immediately cleared and hot, unfiltered, fierce sunshine from cloudless skies (I'm talking mid-to-upper 90's F) has beat down on...wet leaves...leaving nary a burn mark. One caveat: if your water is like mine, and high in mineral content (it's a miracle I don't have kidney stones, lol), when you spray your roses you might see some light residue on the leaves, especially if you end up making it a daily routine/regimen. The residue is harmless, and might even provide some "sunscreen".

I had just mentioned the other day on the "other" forum that anytime the temps here reach the mid 90's I start spraying my roses down. You can literally see the difference in a few days, and there's no worry about spreading BS, because at those temps the spores aren't active; not to mention the leaves dry in minutes! lol. Besides keeping the spider mites under control, the roses may even start setting buds again (mine did), whereas the plants had been in comas during the worst of the heat. After being sprayed down twice daily, my Prairie Peace (a spinosissima hybrid, rare as hen's wisdom teeth) even started throwing new canes this summer...out-of-season and almost unheard of since it's a "cold climate" rose; and that's after it's normal Springtime new canes had hardened off.
So don't be afraid to spray down your roses. Assuming you don't have water restrictions right now, the worst you can do is raise your water bill a bit, lol.
John

jerijen said:Dean -- Water won't burn your rose foliage.

But that does raise a point . . . Have you used ANY Horticultural Oils? (Neem Oil is so popular.)

Because ANY oil on the leaves burns foliage here in Camarillo, on my South-facing hill, if it gets over about 75 degrees. Dilute compounds of dish detergent have done that, here, as well.

No I havent used any oils. I am going to give them a couple of showers per day!

Dean, for 18 years, I gardened in a canyon bottom in Newhall, literally in the canyon where the slopes under the Valle di Oro condos meet those under Scenic Hills, just north of where Golden Valley Parkway meets Sierra Hwy. The weather in those years ranged between 118 and 15 degrees, summer to winter and all the irrigation was by hand and over head. They were the most splendid and healthiest when I was able to allow oscillating sprinklers to run over the tops of the bushes during the heat. The foliage was HUGE and healthy; the plants were HUGE and flowered like the weeds they are and, though the blooms water spotted and some with more papery petals "balled", there was never a better performance period than when I could just let it "rain" on them during triple digit temps. What you show does appear to be sun scald due to the increasingly extreme sun levels and lack of water. Being in the SCV, you should also be aware you now have Chilli Thrips which rasp new growth and flowering shoots. You may not have seen their damage....YET, but they have been in that area for several years and they do attack the majority of the plant types grown as ornamentals as well as food products, so expect to see them sooner or later. You may benefit from contacting the Santa Clarita Valley Rose Society for help in battling them once they hit. They can also assist in teaching you what to look out for. Here is their web site. https://scvrs.homestead.com/ This is where I set up the oscillating sprinkler on a 5' tall stand so it rained over a very wide, long swath of the garden. I had several of them so I could move them around and deep water the entire space while I worked in other areas of it.