So sorry that you are having bad rust problems, Larry.
For what it's worth, the garden spots where I tend to get rust are mostly in the shade, or where irrigation hits the daylilies, or a combination of both.
I have also come to the conclusion that it is better to limit the garden to the more rust resistant plants per the ATP rust scores. Per the ATP database, a plant with a score of 2.4 is considered resistant, but a score of 2.5 is considered susceptible.
I suppose that a line of sorts has to be drawn somewhere, but fwiw I am at the point where if I am considering a plant, and its score is greater than 2.1 or so, I won't get it, unless I absolutely have to have it for some reason or other (such as still rare tet poly genes). And I would prefer to get less than 2.0.... as in 1.5 or less, similar to Becky. (But on the other hand, I have at least one plant here rated a 2.0, 'Full Moon Magic', which has not had rust problems, and I have grown it for over a decade. It may be because it is planted in a sort of out-of-the-way spot, or it may be simply luck, or it may be a matter of different rust strains. So you
can have some clean plants that are rated at 2.0, but I think the lower the score the better your chances.)
Of course the big problem with all of this is that most plants in the database don't have a decimal rust score, and new or recent introductions most certainly don't. Then you have to rely on people posting their gross observations in the database, as to susceptibility or resistance, and those could be wrong. One person's susceptible could be another person's resistant.
If I want to buy a new plant, I now (mostly) try to research its parentage to get some idea of its potential for rust. If it has rusty parents in the background, forget about it. By that reasoning, I will not now buy anything that has 'Wild Cherry Round Up' in its background. I have never grown that plant, and there is no rust score for it in the ATP database, but I have had too many plants with that as an ancestor, and every single one of them has been rust prone. WCR does not have a rust rating, but if you look at its parentage, it has 'Cherry Valentine' (ATP score 5.0) and tet 'Connie Burton' (ATP score 3.0) in its background. I would be amazed if 'Wild Cherry Round Up' were not a rust bucket (in those gardens that were not sprayed, and had active rust).
You can take this principal and extend it to sort of work out your own (half baked) way of estimating rust scores for plants for which there is no data. Trace the heritage back, using ATP scores where available. If no numerical data is available or can be contrived (for an unknown or seedling parent, for example), you can use a 2.5 (borderline resistant/rusty, tending towards rusty). If you have personal observation or experience of an ancestral plant being rusty, you can give it a gross estimation score (say, 3.0) and use that, if that plant appears in the ancestry. Ditto for a plant you have that is resistant (maybe give it a score of 2.0).
(Yes, I realize that some resistant plants derive from rusty parents, and vice versa. I also realize that while such a half-baked score might apply to a large population of children for a potential cross, it is an average and may not apply to any particular individual plant. But faced with a buy/no-buy decision, and lacking direct information as to resistance/susceptibility, I have resorted to this type of estimation to help make my buying decisions.)
I worked out some of these half-baked scores for some plants that I have, and the results were interesting. I will give a few examples:
WINNING NOTE = MEADOW SWEET x TOTALLY TROPICAL;
............................................MEADOW SWEET has an ATP score of 1.0 (resistant, yay)
.............................................TOTALLY TROPICAL has no parents listed, therefore it is assigned an arbitrary score of 2.5
The average score of the two comes to 1.75, still resistant. And that has been my experience of this plant, thus far.
POLLY WOLLY DOODLE = sdlg x BILL NORRIS;
.........................................................sdlg is an unknown, so we give it an arbitrary score of 2.5
.........................................................BILL NORRIS is susceptible with a score of 3.0.
The average score comes to 2.75, or susceptible. (And thus, sadly, has been my experience.)
HIP TO BE SQUARE = BILL NORRIS x ED BROWN;
...................................................BILL NORRIS is susceptible at 3.0
...................................................ED BROWN is resistant at 1.3
The average score comes to 2.15, or slightly resistant. (HIP TO BE SQUARE has shown to have a surprising amount of resistance in this garden, much more so than the score would suggest. So the score is a ball park estimate.)
As a cautionary example, sometimes this estimation procedure can be way off base:
OSTERIZED = YELLOW MAMMOTH x GREEN DOLPHIN STREET
.....................................YELLOW MAMMOTH = HUDSON VALLEY (susceptible, so assign it 3.0) x MONSTER (assign 2.5);
.....................................The average score I would predict for YELLOW MAMMOTH would be 2.75
.....................................GREEN DOLPHIN STREET had significant rust in my garden in 2006, so on the basis of personal experience, I gave it an arbitrary score of 3.0.
The predicted rust score for OSTERIZED would be (2.75+3.0)/2 = 2.875, or rusty.
Yet OSTERIZED has had good resistance here, in the face of shade, irrigation spray, and heavy rust pressure. (As I said in another thread entry, I would recommend this plant to anyone.)
One of my pet peeves is that so many near-white daylilies are rusty, so I wanted to try to find some plants to use to produce seedlings that perhaps are not so rusty. One possible purchase was WHITE PERFECTION. Let's see how it works out:
WHITE PERFECTION = ARCTIC SPLENDOR x WHITER SHADE
...................................................ARCTIC SPLENDOR = sdlg x Tet GENTLE SHEPHERD; In the face of no data for either of these parents, I assigned ARCTIC SPLENDOR a score of 2.5
...................................................WHITER SHADE = PTARMIGAN x Tet HOMER HOWARD GLIDDEN
.................................................................................PTARMIGAN = ARCTIC SNOW (2.3) x WHITE TIE AFFAIR (sdlg x Tet IRON GATE GLACIER, no parentage); assign WHITE TIE AFFAIR an arbitrary score of 2.5, which gives PTARMIGAN a score of 2.4
..................................................................................HOMER HOWARD GLIDDEN has a score of 1.0
....................................................The estimated score for WHITER SHADE is (2.4 + 1.0) / 2 = 1.7 or resistant
The estimated score for WHITE PERFECTION is (2.5 + 1.7)/2 or 2.1.
Normally a score of 2.1 would make me hesitate. But as I have said, I have had at least one plant here with a score of 2.0, that has thus far been resistant. (Or maybe just uninfected.
)
Given that so many near-white tets are so susceptible to rust (by my estimation, ARCTIC LACE is 3.0 , VICTORIAN LACE is 3.53, as two examples), even 2.1 is an improvement and a step up, so I bought the plant. (It is literally a brand new plant, so I have no garden data to give on it.)
This type of half-baked calculation can also be used when projecting crosses. If I have a seedling that I like enough to keep and work with, but I want to improve its rust resistance, I do the same sort of calculation. I have a seedling here which I believe (don't ask me why
) is from a cross involving COYOTE MOON and ONE FINE DAY. The seedling is somewhat susceptible to rust, but not nearly as bad as COYOTE MOON (score of 2.9). (The seedling was hybridized in 2005; I had not been hit by rust then (not until 2006), so I had no rust data and therefore no method of predicting that maybe the cross would not be a good one.) ONE FINE DAY has a score of 1.0, so the calculated estimation for the seedling is 1.95. (I think it is rustier than that...) I crossed this seedling back to ONE FINE DAY, the seedlings from that have an estimated score of 1.475, and thus far
they seem to have good resistance.
Maybe this kind of approach will be useful to some people here, both in purchasing and in hybridizing decisions. Just be sure to keep in mind that any particular
individual plant or seedling may behave better (or worse) than what you might predict for the cross, on a whole.
edited to clarify the situation with the 2005 seedling
