I have never had rust, but I understand the powder is an orangy brown color when the leaf is rubbed. This is the season when I get leaf streak which is brown and yellow discoloration, with the leaves looking dead.

What zone are you in? That will also help determine how serious the problem might be.
kay

There are some photos here...

The spores are bright orange, not yellow and very powdery. If you look at the photos you can actually see little raised bumps. Every fall I go bargin hunting at the local nurseries looking for prennials I refuse to pay the full price for and a couple of years ago almost every Daylily they had was covered with rust, so yes nurseries can be a source of rust. If you decide to speay make sure you use a systemic. The first time I had it here I used a contact spray which looked like it was working but the rust kept coming back. I eventually gave up and let it run it's course. I am in Zone 5 so winter kills it. I had it in 2005, 2006, and 2007. I have since changed my buying habits and have not seen it again. I no longer buy from people in the south or areas without the extended cold spells it takes to kill it. If they buy new intros from the south I get them to send my plants out as early as possible to avoid their new plants sending it here.

It is unsightly but I cannot say it has actually killed any plants here. I am sure it set some back and they did not preform as well the following years.

Leaf streak can look like rust, look for the little RAISED bumps and the orange powdery spores. I was out in the garden this morning and saw 1 case of leaf streak that made me check to make sure that's what it was so even though you have seen rust a quick view of any miscolored leaves tends to make you think about it.

It is not the end of the world either.

Here is a link that might be useful: Rust

Do you have winter in the SF Bay area? If you do then that is good as winter will kill the rust. But if no winter that is a problem as you can treat but not cure.

So maybe it is leaf streak instead. Is there anything that I can do about that? I have some flowers coming from the daylilies that have this leaf issue but they hardly look healthy (the flower petals are wrinkled and almost look ripped).

The Stella D'Oros in the front yard that have healthy looking leaves had nice perfectly formed blooms.

I'm in USDA Zone 9, 10 and we've had crazy weather here this year: lots of rain in the winter and yes, we do get frost. We actually just had record rain over the weekend.

Take a kleenex and pull it along the leaves. If you see any orange powder then it is rust. Your weather will not be cold enough to kill it unfortunately.

If you believe it is rust, you can dig them up, cut them back to about 8" or so above the crown, and soak them for 30 minutes in a 10% Clorox/water solution. Replant them away from where you plan to plant your daylilies, even if you have to put them in pots.

I haven't found rain to cause rust to increase. In our country garden, it was warm days and cold nights with dew-covered plants by morning. That creates the environment that brings on rust, if it is indeed that. I'd talk to some other daylily folks in your area to see if they have ever had rust.

The best systemic for rust that I know of is Nickel Plus, but you have to be very, very careful when using it.

Nancy