Hi,

I spend hours looking for rust-resistant daylilies. I rely on what the database says and what certain breeders say. But over and over members say a daylily gets rust where the database gives it a 1.0 -1.8 rating. (Just read another post.)

Or it may be labeled as "shows resistant".

Please, if you have a daylily, new or old, that got rust even after being in your garden rust-free for years, please change the rating. If you got a daylily from the south and some of your daylilies caught it, which ones?

Near the plant name just click "edit" and under "rust resistance", please pick "shows susceptibility". Doing a change on the digital rating can be tricky, so not asking for that, unless you want to.

Some professional hybridizers care and are making a difference, like Gossard, Brian Reeder and John of Greenwood.

Thanks for your help!

Bob

I'm surprised it's even possible to change the numerical ratings since they were compiled from specified published research:

https://garden.org/barn/notes/...

It would be nice if someone could incorporate the stats from this survey:

https://www.researchgate.net/p...

The shows susceptibility or resistance section reflects only the opinion of the last person who changed it, so theoretically it can just switch from one back to the other at any time. I would ignore any rating of "resistance" in that section, personally.

I think I did change the susceptibility rating from resistant to susceptible once, but when I thought that was only one bad season I was not able to change it back. Seems I was told once it showed as being susceptible then it was. I used to put a lot of faith in the ratings but not so much any more, I still use them as a general guide.

Seedfork said:I think I did change the susceptibility rating from resistant to susceptible once, but when I thought that was only one bad season I was not able to change it back. Seems I was told once it showed as being susceptible then it was. I used to put a lot of faith in the ratings but not so much any more, I still use them as a general guide.

Well if you can't change back from susceptible then that would be a good thing - even if it was a bad season it doesn't make any difference, if it showed rust it is susceptible.

I guess my thinking was and still is, that being resistant does not mean a plant will never get rust, but will resist getting rust. If it has rust one season and no rust for three or four seasons then I would consider that to be resistant. That is probably not the official thinking but in my garden I do appreciate plants that tend to seldom show rust and consider them resistant. I would not be able to list a single plant off hand that never shows any rust. but many do better than others.

The survey of rust on 575 cultivars used a 1-3 rating system as follows:
"1 = no or little visual sign of infections; 2 = moderate infection; 3 = severe infection. "

However, other research used a 1-5 rating, for example,
"Plants were evaluated for rust development and severity five times from 9 to 21 days after inoculation using a 1 to 5 rating scale where 1= no disease, 2= reduced lesion number and lesions did not produce urediniospores, 3= reduced lesion number but lesions still produced urediniospores, 4= slightly reduced lesion number and/or reduced amount of sporulation, and 5= fully susceptible."

How were these different scales combined? How were the effects of different test periods combined?

As a personal challenge, I am going after a rust-free breeding program for daylilies.

It is a difficult goal to plant only resistant daylilies. I have to pass on so many I would like to own because I have no proof it is resistant and that's most daylilies. A highly suspectable plant will get rust immediately in my garden.

If I do get a plant or seedling that gets attacked by rust, I will pitch it. Wasted money. I do want to bring in some to test, like some of Stout's evergreens. I am going to hate to secure these heirlooms just to turn around and pitch them.

It is interesting when I ask sellers if they know which ones are resistant in their growing "fields". Most will say no. But occasionally one will give me a very small list.

sooby said:
The shows susceptibility or resistance section reflects only the opinion of the last person who changed it.

And I'll take that opinion. It's better than "no opinion" like on 95% of the daylilies listed.

@bobjax

It is a difficult goal to plant only resistant daylilies.
If I do get a plant or seedling that gets attacked by rust, I will pitch it.

To breed for rust resistance you need rust to be more or less rampant in part of your breeding area to test for the resistance of seedlings - thus you need to grow susceptible daylilies.

bobjax said:

And I'll take that opinion. It's better than "no opinion" like on 95% of the daylilies listed.

How would a change from susceptible to resistant be useful (assuming such a change is possible in the DB)? It would pretty much indicate that either someone has a mis-labeled plant, the environmental conditions where the plant is growing in their garden were not conducive to rust development, or.............. A daylily that is susceptible in one garden is genetically susceptible, that doesn't change.

Of course it's all a matter of degree, in plant pathology "resistant" does not mean immune and resistant plants can still get rust.

admmad said:

How were these different scales combined? How were the effects of different test periods combined?

The link I gave above on the origin of the numerical ratings has a paragraph that says they were averaged. I don't know how Chalyse actually did it and I don't think she is still active on NGA.

sooby said:

How would a change from susceptible to resistant be useful (assuming such a change is possible in the DB)? It would pretty much indicate that either someone has a mis-labeled plant, the environmental conditions where the plant is growing in their garden were not conducive to rust development, or.............. A daylily that is susceptible in one garden is genetically susceptible, that doesn't change.

Of course it's all a matter of degree, in plant pathology "resistant" does not mean immune and resistant plants can still get rust.

If I buy a daylily because it is labeled as "resistant", I spend money and time on the plant. But if within a month of planting rust starts to seriously take over the plant, I remove the plant and submit a request to change the rating. Seriously, probably has not been many, if any, changes from "susceptible to resistant". If you say a daylily gets rust in your garden in Canada, I believe you. I just move on to the next plant. But if it says "resistant" and it is not, I feel obligated to request a change.

Unfortunately the resistance of any daylily to rust is likely to change with time to susceptibility to some races of rust. Rust changes with time and "defeats" the resistance of cultivars.

Further to Sue's comment that even daylilies identified as resistant or highly resistant get rust, 'Stella de Oro' is described as follows in one research paper on rust, "Prairie Blue Eyes, Going Bananas and Stella de Oro were resistant or highly resistant, and Mardi Gras Parade was highly resistant to the 16 isolates of P. hemerocallidis" meaning Stella was resistant or highly resistant to all 16 different rust lines. Yet two of those lines had been produced from rust infections present on different Stella plants in different locations.

admmad said:...Further to Sue's comment that even daylilies identified as resistant or highly resistant get rust, 'Stella de Oro' is described as follows in one research paper on rust, "Prairie Blue Eyes, Going Bananas and Stella de Oro were resistant or highly resistant, and Mardi Gras Parade was highly resistant to the 16 isolates of P. hemerocallidis" meaning Stella was resistant or highly resistant to all 16 different rust lines. Yet two of those lines had been produced from rust infections present on different Stella plants in different locations.

I guess we should have faith that the researchers exercised care in their acquisitions, but browsing through the database here, it appears that there are a few different cultivars being offered in the trade as Stella de Oro. It's understandable, Stella was unbelievably popular, and was used by many hybridizers who wanted to work that continuous bloom into their lines. The problem was, many of the seedlings bore an uncanny resemblance to Stella, and it's not unreasonable to suspect that a lot of those seedlings were passed off as Stella, particularly to landscapers and the nurseries who catered to them. Stella also sets plenty of bee pods, and if those seeds germinated in the clumps...

@JamesT Although the observations may not be as dramatic for other cultivars (they were not used to collect any of the tested rust strains) similar situations existed for the highly resistant 'Hush Little Baby' that was highly resistant with no visible symptoms to 15 of 16 strains but only moderately resistant (became infected and produced spores) to one strain. Or for 'Joan Senior' that was highly resistant with no visible symptoms to 14 out of 15 strains but only moderately resistant to one strain. The rust strains used in the tests were collected between 2009 and 2012. There are likely to be more different rust strains now and the cultivars would probably show less resistance overall.

I just saw a post on a FB forum which belongs to a major daylily seller. She posted her spraying schedule including chemicals. If I counted right, she uses 7 different chemicals to spray her daylilies on a regular schedule. That does not include fertilizers.

I use none and will attempt to keep it that way.

When I grew roses years ago, I wanted a no-spray garden because of pets. I finally ended up with only 2 roses, out of many, many that were not immune to disease.

Fortunately we have at least three breeders out there who focus on developing rust-resistant daylilies, so hopefully, I will end up with more than two daylilies.

Regarding the discussion of more than one type of rust. Different rusts can show up anytime. Brian Reeder looks at a daylily for 5 years before he labels resistance.

There is one daylily, very common, with great resistance, yet one member on Garden dot org said that after growing that daylily rust-free for years, one year rust hit that daylily hard. So far in my "high-rust" environment, I have no zero rust on it. So rust-resistance is complex. But that's my challenge.

Just to clarify something for anyone not familiar with rust diseases in plants, when we talk about "races" on this forum, these are genetic variations of the same fungus, Puccinia hemerocallidis, which is specific only to daylilies, certain Patrinia species and Dianella tasmanica.

There are thousands of different plant rust fungi and all tend to be limited in the number of specific plants they infect. Many of them are also in the genus Puccinia but no other rust fungus but P. hemerocallidis infects daylilies, in other words while rust diseases tend to like similar environmental conditions thus you may see an infection on various different plant species at the same time, it does not mean that a single pathogen has spread to all of them. Rust on your hollyhocks, roses, grasses, or any other plant won't spread to your daylilies.

sooby said: Rust on your hollyhocks, roses, grasses, or any other plant won't spread to your daylilies.

Regarding roses, I meant black spot and mildew.

https://www.daylilies.org/ahs_...

admmad said:@bobjax

To breed for rust resistance you need rust to be more or less rampant in part of your breeding area to test for the resistance of seedlings - thus you need to grow susceptible daylilies.

That's what I thought, also. I know one breeder who brought in rust from Florida just to test against it.

In my daylily garden, when I first started, I got rust within a few weeks after I planted daylilies that were rust magnates. When I got them they came in clean from growers who spray.

Recently I started a seedling bed completely remote and isolated from my other daylilies. Some got rust at 3-5 weeks old. I had zero rust on any of my other mature daylilies at the time. I read that certain weeds harbor it and that it is the air. My garden can be clean and if I bring in a rust magnate it gets rust quickly.

In the north where winter kills rust, breeders might have to take special efforts to bring in rust to test for it. Down here and in Georgia, if growers could simply get rid of rust once, then they would never have rust again that would be great. But everyone has to spray big time to keep it out. As they say, it's in the air.

bobjax said:

That's what I thought, also. I know one breeder who brought in rust from Florida just to test against it.

Brian Reeder, who you mentioned above, is one that has brought rust in from other places since it doesn't overwinter for him, although I don't know whether he still does that.

bobjax said:
In my daylily garden, when I first started, I got rust within a few weeks after I planted daylilies that were rust magnates. When I got them they came in clean from growers who spray.

While daylily rust can develop visible symptoms in about 9-14 days following inoculation, it can also have a long "latent period" during which no external signs can be seen. This may be because of adverse environmental conditions, but it may also be worth noting that many of the fungicides people are using only suppress the disease rather than kill it.

bobjax said:I read that certain weeds harbor it and that it is the air.

If by weeds you mean the alternate host, Patrinia spp., which are sometimes grown in gardens as ornamentals, then yes in Asia that is a factor that can allow daylily rust to persist year to year even where the daylilies are deciduous in winter, but so far Puccinia hemerocallidis has not been shown to use Patrinia plants in North America. The variant on Dianella tasmanica was tested and although it was deemed to be the same fungus as daylily rust, spores from one would not infect the other experimentally. Other than these two plants, nothing else besides daylilies are known to "harbor" this rust fungus. But yes, in areas where it is endemic there will be spores floating around in the air, and spores can also be moved more locally by splashing rain/irrigation.

If you'd like to know more about how this rust works, what plants are affected by it, pictures of the different spore stages etc. you may like to visit this web site devoted to daylily rust:

http://web.ncf.ca/ah748/rust.h...