Rust

General Discussion
1

It has been known for some time that a new rust variant has appeared.

Many hybrid teas are affected, floribundas not really.

Also some of the Knock Outs, such as White Knock out have rust.

What experience do you have?


Many greetings
Andrea,
Germany, near Heidelberg

2

Here in California, rust is the main rose disease. There are a number of breeding lines I won’t touch because they are guaranteed to rust. Playboy, Queen Elizabeth, nearly anything Hybrid Rugosa, nearly all Hybrid Arkansanas are guaranteed to rust here. Knock Outs? Oh, yes, mildew and rust. While they may not spot easily, they WILL easily mildew and rust. There are still many HTs and floribundas which seem immune to both. Blue for You, Eyes for You, Art Nouveau, Irish Hope, Chandos Beauty, Davidson’s Golden Oldie, Grimaldi, most old Teas and Tea Noisettes remain clean.

3

California is a very large state with many climatic variations. There is, like in most states, University based agricultural extension service publications which provide information for their climatic conditions. This is what was last updated 2/2020.

4

This seems like a good place to mention older efforts to breed for resistance to fungal infections.

http://bulbnrose.x10.mx/Roses/breeding/FishRoseRust1898.html
Fish: Orange-fungus on Roses (1898)
I have long known that the red-rust seldom or never attacks Teas, Hybrid Teas, Noisettes, Bourbons, Chinese, or Banksian, or smooth shining-leaved Roses. Even such Perpetuals as Boule de Neige, the Verdiers, and other more or less smooth and shining-leaved hybrid perpetuals escape the orange-fungus. Can it be that this pest cannot lay hold of or remain long enough upon the leaves to effect its reproduction? Suppose we try to starve out this fungus by offering it nothing to feed upon but smooth semi-shining varnished-leaved Roses.

http://bulbnrose.x10.mx/Roses/breeding/KordesRoses1955.html
Kordes: Breeding Disease Resistant Roses (1955)
Then the first Poulsen roses appeared and showed that by breeding in Rosa multiflora the rust and black spot could be got rid of. Only mildew remained in some of the varieties. This gave me the idea that it should be possible to get rid of all the three major fungus diseases, mildew, rust, and black spot, by breeding in hybrids of Rosa moschata into our garden roses.

http://bulbnrose.x10.mx/Roses/breeding/Wyatt_Teas.html
Wyatt: Tea-Scented Roses (1975)
One very good reason which may be advanced for their survival is their ability as a class to withstand the debilitating fungal infections, mildew, black spot and rust. While it cannot be said that they are entirely immune, their resistance to these infections as a class is considerably higher than the Hybrid Teas and Floribundas. Only one variety, ‘Adam’, has shown any real susceptibility to mildew—a factor which helped to confirm its identity! These observations are supported by reports from rosarians now growing Teas in various parts of the country who have been kind enough to keep me posted.

http://bulbnrose.x10.mx/Roses/breeding/Persica/PERSICA.HTML
Harkness: Breeding With Hulthemia Persica (Rosa persica) (1977)
Our plants of H. persica, however, once grown past the seedling stage, have been extremely healthy; as also have been the hybrids. I cannot recollect seeing mildew, blackspot or rust on any of them.

PS: The first time I ever saw rose-rust it was on Rosa setigera growing at K-State. It was on a lawn. I don’t recall seeing this species bothered by rust growing wild in Kentucky or Tennessee.

5

I added a link to a paper by Dr. Kermani et al., 2009 characterizing various species of fungi causing rust in roses. This seems like a pretty diverse group of pathogens for having such a variation of species causing similar symptoms and growers calling it all by the same disease name. http://www.globalsciencebooks.info/Online/GSBOnline/images/0906/FOB_3(SI1)/FOB_3(SI1)126-130o.pdf

My R. setigera gets a lot of rust too Karl. It seems kind of different for how aggressive it is on the stems and flower buds of the R. setigera plants. The interspecific hybrids of these R. setigera all seem to be clean for it and the other roses don’t seem to have it at least appear and grow in the say way on them.

It would be great if more work could be done studying the variation of rust out there and what resistance genes are in roses for us to try to be more strategic in breeding for resistance that may have wider effectiveness across different forms and hopefully regions.

6

I find this quite an interesting topic. I noticed that alba roses will easily get rust. Also, rosa spinosissima at my coast gets rust. A very peculiar orange color btw… and when I visited Denmark 2 yeatrs ago, I found some other wild roses, probably rosa villosa, that were also affected by rust.
I find it quite interesting to read Karl that using multiflora(hybrids) into a breeding program would bring resistance te rust.
I wonder… has any of you seen rust on any moschata roses (most of these have multiflora influence). What about Trier, Danae, Pemberton’s roses, Lens’ roses, …

7

I read in the paper that KORbin, aka Iceberg is resistant to rust (phragmidium tuberculatum). It would be interesting to know if it got it’s resistance from Robin Hood (might be likely since it is classified as a moschata??) or Virgo.

8

REply to Karl. I have what must be that same R setigera from K-State. Until last spring I had never seen rust on it as it kept struggling along in the weeds. But I took cuttings the previous fall to grow plants for comparison with plants that I got from David Z. Long story, but because of the COvid nonsense, I had to move a bunch of stuff home from work and I created some temporary coldframes to keep small roses alive outside in March- a challenge. Later i left them under glass with sides open and got phenomenal mildew and rust crops. Perfect conditions, sunny dry days, cold nights, lack of watering. The K-state line, which I had guessed was from an Ohio nursery about 75 years ago totally defoliated. A fungicide kept it alive, but it is clearly very different from the ones originated at the Minnesota Arboretum, which got its stock from I forget where. Huge difference within species…

9

Hi Larry,

If I remember right the ones I sent trace back to seed sent from Boerner Botanical Gardens in the Milwaukee area in the 1960’s or early 1970’s, but I couldn’t find information on where they obtained their plants.