Rust! I have rust. For the first time ever, rust on my roses. Not on my tough-as-old-boots Rosa ‘New Dawn’, but on my I-had-such-high-hopes-but-it-seems-they’re-coming-to-naught David Austin rose, R. ‘William Morris.’
Rust is a fungal disease, which spreads by spores. Sometimes, rust on roses is co-hosted by junipers, so I’ll have to inspect the tree in my neighbour M’s back yard.
As nine-tenths of pests and diseases have a cultural basis, however, I think I have only myself to blame: I moved ‘William Morris’ earlier this year, reducing its root system. Then we had that hot spell in April. It’s likely that the combination weakened the rose. With the recent cold, wet weather, the rust was ready to move in and found a willing host.
Here’s what the rust fruiting bodies look like on the back of the leaf.
You can control rust with a sulphur treatment, which is one of the things still permitted under the Ontario Pesticides Ban. So far, as it’s not too widespread, I’m taking the first line of defense, which has been to carefully remove the rusty leaves and discard them. Hopefully, that will delay the spread. Cross your fingers.
I knew Juniper's give fruit tree's trouble, but I didn't relizes they bother the roses. I've never had rust, but I get black spot. Pain in the…..
O wow I am so glad you posted this. I live near the Falls (Canadian Side)so same conditions as you up there in Toronto. I checked all my Roses to-day as well as other things and no rust just yet any way. I will keep an Eye on this for sure.
I have found also to compliment your Sulpher suggestion is to keep the rain and watering completely off the plant. The Water drops splattering spreads the rust spores and contaminate even worse.
I've never seen this condition before. It was dryer where I used to live. Thanks for bringing it to my attention. I hope things work out!
If it's any consolation (& it won't be), I have rust just starting on new David Austin roses – and blackspot – too. So much for being disease resistant or, perhaps, it would be worse if they weren't. Who knows!
Laura, Many fruit trees (such as apples, cherries, peaches, and even almonds) are in the larger rose (Rosaceae) family, and are susceptible to to some degree. What happens is that Junipers co-host the rust, and share it back and forth with the rose-family at different stages of its lifecycle.
Reg, I'm glad you mentioned not watering the leaves and not splashing the soil upward when you water. That's very important to control of rust and other fungal diseases. Can't do too much about the raindrops, however.
Aerelonian and Johnson, As I wrote, this is the first time I've had this problem in my garden on roses*. The 20+-year-old New Dawn, which is planted nearby, has no sign of it, touch wood. However, the leaves of the David Austin rose are much less glossy, so perhaps were a better target. Plus, as I said, moving the rose likely weakened it, compounded by unseasonably hot weather.
*I do get rust on my hollyhocks. But then, who doesn't?