Hi Vickie, I live in Georgia and have battled with rust over the last few seasons. I had some success last year after following some guidelines set out by Dr. Scott Elliott who grows and hybridizes daylilies near Savannah, GA. However, if you are strictly and "organic gardener," his use of chemicals will likely turn you off. I live about 150 miles northwest of Savannah and I usually see rust in the spring as temperatures pass from our winter cool weather to our summer hot/humid weather, then again in late September and October after temperatures drop back below the 85 degree mark with a much smaller amount hanging on during the summer. Scott wrote a 3 page paper in our Region 5 magazine early last year which described not only his methodology, but gave some background on daylily rust, its reproduction cycle and methods of control. It sounds like you are beyond the "protection from rust" stage, and possibly beyond the "remove infected plant tissue" stage that Tink described. Scott goes into considerable discussion regarding fungicides and how they are divided into contact and systemic, but also into how they are divided into groups based on how they actually function - - which brings him to a discussion of the the FRAC code (Fungicide Resistance Action Committee). This is extremely important because the use of a single fungicide or multiple fungicides which are from the same FRAC code may lead to mutations in the fungus and resistance to that class of chemicals.
Here are his recommendations:
1. Always use a mix of one contact and one systemic fungicide in a single application.
2. Systemics must be applied in rotation - that is, application #1 uses one systemic fungicide and is followed 10-14 days later with an application using a different systemic fungicide from a different FRAC code.
3. He suggests using neem oil not for any fungicide properties, but for its ability of coat the foliage, thus making it more likely that the contact fungicide will in fact contact all they pustules on the foliage.
4. He also states that pure neem oil must be mixed with an emulsifying agent before adding to the mix because like almost all oils, neem oil and water do not mix with each other. He uses a dish-washing liquid for this purpose. There is a pre-emulsified neem oil available on the market, but it really jacks up the cost.
There are some other things that he mentions, but these are the highlights. However, that still leads one to ask "Yeah, sure. That's wonderful, but which chemicals does he use?" Here is his list:
Contact fungicides: Cholothalonil (Daconil or equivalent) or Mancozeb (Dithane or equivalent)
Systemic fungicides: FRAC code 11:Pyraclostrobin (Cabrio) or Azoxystrobin (Heritage)
FRAC code 1: Thiophanate Methly (Cleary 3336 or equivalent)
FRAC code 3: Propiconizole (Banner Maxx or equivalent) or Myclobutinil(Systhane or eq)
The positive: I had pretty good success with a rotation of these chemicals (along with neem/dish soap) when applied every 14 days. No, it didn't kill the rust 100%, but it really knocked it back and it did appear to kill the rust on many of my daylilies.
The negative: The systemic fungicides are EXPENSIVE!!! Anything from code 11 is very expensive. Cabrio is the least expensive, and that is not to infer that it is cheap. It is not, it is just less expensive than Heritage. Code 3 products can be found in your local big box store. The code 1 products are harder to find unless you are in major metropolitan area and are willing to call a lot of specialty stores until you find it. The code 11 products are internet purchases for me.
I hope this helps, but it will probably depress you when you find the prices for some of the products. Do others in your area have a similar problem? I'm surprised that with the winters we all had this year that rust is already so noticeable in your garden. We actually got below 10 degrees a couple of times here this winter and had an ice storm that shut down this entire area for nearly a week (downed trees, electrical lines, etc.) and I know you had it colder and for a longer time than we did. Of course, we went from winter to summer with only about two weeks of spring. It hit 90 degrees the first time in mid-April and has been 90+ every day the last couple of weeks and rust does not reproduce nearly as well when the temperature is over 90.
Good luck,
Larry
