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 ...
), 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?