I am trying to keep track of the rust infestation in my garden for breeding purposes. Is there somewhere I can find the rust number ratings and how those numbers are determined? I want to rate my daylilies, but not sure of the numbering system.

Thanks in advance for any help with my question!

Isn't ATP trying to incorporate the rust rating in the database?? I thought I saw that mentioned on here somewhere. I did check the listing for Galaxy Explosion because that plant is supposed to have some good rust resistance but I did not see any rust rating listed.

Cindy - ATP database does have a rust rating for some daylily cultivars, but most are not rated. I am trying to determine the number system for rust. I believe that a rating of "1" means highly resistant. I just don't know what the various other numbers would be from highly to the least rust resistant. Does the rating go from 1 to 10? Or 1 to 5? Or what? That is what I am trying to determine. I want to rate the daylily seedlings I am growing to determine what to use in my hybridizing efforts.

I also need to know what rust characteristics are determined for each number rating. I sort of know the different levels of rust infection as I can see different levels of rust infection on different plants. But I am just not sure which number in the rating system would apply to each plant per their level of rust.

The explanation page for the ATP rust scores can be found here

http://garden.org/barn/notes/r...

This page can also be accessed by this link "Read our note about daylily rust scores" at the bottom of any cultivar page.

Thanks Char.

Char - Thank you. I guess I never paid much attention to any footnotes at the bottom of each cultivar listing. Can't see the tree for the forest.

Are there photographs anywhere showing the amount of rust for each rating? Or a more extensive explanation of each rating? The wording is rather vague to me between numbers.

Also, I do not understand what it means between "horizontal resistance" and "vertical resistance". Can someone clue me in about this in layman's terms?

beckygardener,
I think you will enjoy this article, it explains just a little about horizontal and vertical resistance. Something to do with single major resistance genes or a combination of genes causing resistance. A lot of other good info also.

beckygardener said:Also, I do not understand what it means between "horizontal resistance" and "vertical resistance". Can someone clue me in about this in layman's terms?

Vertical resistance means resistance is related to a single gene and is specific to an individual race of the pathogen (meaning a plant cultivar may be susceptible to one race but not to another). Horizontal resistance involves several genes and can protect from all races of a pathogen. Horizontal resistance is less prone to a breakdown in resistance than vertical resistance because with the latter there is only one resistance gene for the pathogen to overcome. With horizontal resistance you can still see some disease on the plant but to a minimal extent.

That's the theory anyway, and this is probably an oversimplification (for both our benefits)! @admmad would be able to explain better.

Out of 32 plants that I have had bloom so far this Spring (which is when I do the bloom/scape measuring and checking for rust):

8 plants show no rust whatsoever.
7 plants rate somewhere on a 2 scale (If I understand this rating correctly)
6 plants rate somewhere between a 2 and 3
10 plants rate between a 3 and 4
1 plant rates between a 4 and 5

But those numbers are only accurate if I understand the definition of each rating.

The seedlings that show the most resistance at a number 1 rating, have no sign of rust on them at all. None. There are rusty daylilies around them with some rusty leaves even touching their leaves. The seedlings are:
3 Laughing Clown x Zanti's Misfit (3 siblings) (CCC01, CCC05, and CCC08)
2 Laughing Clown x Instant Graffiti (2 siblings) (CCC03 and CCC06)
1 I am uncertain about the parentage (it looks like it might be a spider or UF type of daylily) (CCC17)
2 Galaxy Explosion x Lily Munster (2 siblings) (ZZZ37 and ZZZ38)

NOTE: All those above that are rated a 1 are spiders or look like spider form.

Rating #2:
1 Laughing Clown x Instant Graffiti (1 sibling) (CCC09)
1 unknown parentage I marked as CCC07 (a pretty pink bloom that is NOT a spider or UF)
1 unknown (CCC14) this is a large deep red bloom with yellow throat - very attractive bloom and foliage (not a spider form)
1 Francis of Assisi x unknown (CCC19)
1 unknown reddish-orange spider form (CCC21)
1 unknown orange w/yellow throat spider form (CCC22)
1 Galaxy Explosion x Lily Munster (ZZZ43)

Rating between a 2 and a 3:
1 Cherry Custard Cheesecake x Palace Garden Beauty (ZZZ31)
1 Laura Mast x Dragonfly Dawn (ZZZ73) This is the double bloom seedling
1 Through the Looking Glass x unknown (CCC04)
1 Stippled Statement x unknown (CCC11)
1 Bird Talk x unknown (CCC13)
1 Drink the Light x God Save the Queen (CCC15)

Rating between a 3 and 4:
1 Through the Looking Glass x unknown (CCC02)
1 unknown pink (CCC10)
1 Paper Butterfly registered daylily (CCC12)
1 Victorian Lace x unknown (CCC16)
1 Soft Summer Night (CCC18)
1 unknown red with yellow eye (CCC20)
1 Laura Mast x Dragonfly Dawn (ZZZ72)
1 Cedar Point (ZZZ61)
2 Dragonfly Dawn x Dragonfly Dawn (ZZZ66 and ZZZ67) Sad, but true!

Rating between a 4 and 5:
1 Hotter than the Fourth of July x Rorschach Test (ZZZ71) (This one looks like a rust bucket ... much to my dismay) It has a sibling right next to it that hasn't bloomed yet that also looks very rusty.

It's encouraging to see several that rate 1, and discouraging to see a possible 5. And of course, my favorite daylilies are at least a 3 rating or worse. (sigh)

I will be trying to cross the rust resistant daylilies with the pretty faces! I want the best of both, but we shall see which genes dominate in the breeding trials.

Something else to note: None of the spiders rated below a 2.

Sue - Has there been any cultivars that are both horizontal and vertical rust resistant?

So let me verify this .... even if I have rust resistant daylilies, that does not mean they are horizontally resistant? They could just be vertically resistant, correct? I have no idea how many races of rust they are exposed to in my garden. It might only be 1 or a few races, but not all. (Which is probably most likely.) I do have a LOT of rust in my daylily garden beds, so at least one race of rust is running rampant here!

As far as I know nothing has been published on this in daylilies so it would mean speculation based what little we know. Maurice would be better qualified to speculate on anything genetics-related than me, so hopefully he will join the thread.

Sue - Thank you! I do hope Maurice @admmad will join this conversation, too.

beckygardener said:Are there photographs anywhere showing the amount of rust for each rating?

It would be very useful if someone would make a set of photographs or drawings showing examples of the amount of rust on daylily leaves for each rating. Below is an example used for wheat. It cannot be used for daylilies as they may or may not have as much rust on their leaves as wheat does.




Sue's explanation of horizontal and vertical resistance is reasonable. In practice there are difficulties with categorizing plant resistance no matter what simple systems one attempts to use. Living organisms seldom obey our simple 'rules'.

It is not known whether daylilies show horizontal or vertical resistance to rust. It is possible that some cultivars show vertical resistance and other cultivars show horizontal resistance - we do not know. By definition a cultivar could not show both vertical and horizontal resistance.

even if I have rust resistant daylilies, that does not mean they are horizontally resistant? They could just be vertically resistant, correct?

More or less correct but it depends.
In some cases of horizontal resistance the plants would still get some rust just not enough to cause problems or so late in the season that it does not matter. In some cases of vertical resistance the plants would not get any rust. However, it would be very difficult to know which type of resistance is present by simply observing rust in a garden.

I've noticed some plants get rust quickly but can also recovery quickly.
Some resistant plants with #1 rating can hold off rust for a long time,
but when they show it are almost overcome by it and take longer to recover.

Garden location matters -- early morning sun, air circulation, temperature, humidity, etc.,
as does fertilization and soil mineralization, how long the plants have been in place
and haven't been divided since moving seems to weaken them.

Some plants attract every rust spore passing by no matter what.
If rusty leaves touch a resistant plant long enough, the resistant plant will eventually get rust.

There's more on "vertical" and "horizontal" here:
http://daylilybreeder.blogspot...

Maurice - Thank you for chiming in concerning rust evaluation. I am really surprised that there has not been a series of photographs taken to show the different rust ratings. I really need to see some photos to be able to accurately evaluate my plants.

Maybe I should take some photos so that perhaps others here can tell me what rating the rust is on each leaf? I would be more than glad to do that. Would that be possible to tell just by photographs of leaves?

Pat - I have followed Brian Reeder's blog and find his methods very practical. On this page ...
( http://daylilybreeder.blogspot... ), he wrote and I quote,

"Learning to properly evaluate the level of rust on any given cultivar is not easy, but it is also not extraordinarily difficult. It is not impossible! It can be done and I have faith that you can do it. There are some simple points to consider that will help. In some instances, the rust actually manifests in ways that can help you determine what you are seeing. It is not uncommon to see rust on fairly resistant cultivars clustered only on the tips of the undersides of the leaves, or in some instances, at the bases of the leaves. In those instances, you can fairly easily gauge how much of the underside of the leaf is covered just by measuring how long the leaf is, and then how much of the leaf is covered in rust, or you can then prepare an average from several leaves on that cultivar for even more accuracy overall. A little math is required, but it isn’t a quantum formula.

In other instances, the rust may be scattered over the entire surface of the underside of the leaves or on both sides of the leaves, much like a scattering of salt. The amount can vary widely. The easiest way to come to a conclusion of coverage in this instance is to attempt to judge how much leaf is showing through the salting of spores. This is more difficult to gauge than when the rust is restricted to a specific portion of the leaf, but it is not impossible to gauge. I hope in the future that we can come up with a series of photos showing leaves with different levels of rust to create a general visual guideline for those new to evaluating rust levels, but until that gets done, I hope these general ideas can help you to make some fairly accurate evaluation assessments in your own garden."

~~~

So in reading that information, the rust rating is determined by how much rust covers the leaves?

In all honesty, the plants in my yard that get the most rust also seem to be the ones that get the most sun. I have a lot of daylilies that receive some shade during the day and most all of them look pretty good. Not an overwhelming amount of rust. Could rust infestation be dependent on the stress of the plant? If my daylilies get too hot and dry because of too much sun, they appear to be more prone to rust?

the rust rating is determined by how much rust covers the leaves?

Yes.

One can modify that.
A cultivar that has leaves 20% covered with rust in June should have a different rust resistance rating than one that does not have its leaves 20% covered with rust until November. To make certain those two cultivars receive different rust ratings one would rate them both at the same time (say in June).

More scientifically one would examine the amount of rust on the leaves of the cultivars many times during the year and then graph the results. From the graph one could see when rust first appears on different cultivars, the speed at which rust develops on different cultivars and the final amount of rust that develops. It is possible that all three measures are different between cultivars. On the other hand it may be that the measures are related.

beckygardener said:
In all honesty, the plants in my yard that get the most rust also seem to be the ones that get the most sun. I have a lot of daylilies that receive some shade during the day and most all of them look pretty good. Not an overwhelming amount of rust. Could rust infestation be dependent on the stress of the plant? If my daylilies get too hot and dry because of too much sun, they appear to be more prone to rust?

It may depend if the soil analysis (amount of nitrogen and potassium) is different between the two places or there is some other environmental factor. Rust spore germination is inhibited by high light - infection is most likely to happen between evening and early morning when the leaves may be wet, the temperature optimal and the light low according to Mueller and Buck's paper Effects of Light, Temperature and Leaf Wetness Duration on Daylily Rust. Plant Disease. 2002 Vol 87 No. 4 442-445.

The environment is not as much of a factor once the infection is established. Having said that, other people say rust is worst where it is shady which is what one would typically expect. It may depend on what's causing the shade and where the bed is in relation to it. Shade would keep the light lower and the leaves wet longer, things rust likes.

Stress is a controversial aspect. Some experts say it actually reduces rust others say it depends on the stage in the lifecycle. There was a lengthy article years ago about how stress from insects etc. can reduce rust on other plants, but I'd have to find it again. The idea is that since rust needs living tissue to survive then it will do better on a healthy plant. If you think about when daylilies are shipped, that's a huge stress, yet often they can be carrying rust that doesn't develop for several weeks after they arrive.

We only see the rust once it has produced spores, we don't see it when it's happily feeding away inside the leaf and stealing nutrients before it sporulates.

Maurice - Thanks for mentioning that. I did read that somewhere and understood that timing also figures into the rust rating.

Is there ANY PLACE that states a description of rust coverage including a rust percentage on the leaf for each rust rating from 1 to 5. The only two I even have a clue about is 1 and 5. The ratings in-between the low and high number elude me.