DAYLILY RUST
I have had a number of people write me regarding rust (Puccinea hemerocallidis) and its detection, control, elimination and prevention. There are many fallacies regarding rust and I hope to dispel at least the more outrageous of them.
To determine if what you are seeing in your garden is rust and not leaf streak, which can look similar, run your finger or a paper towel over the suspected rust pustules. If you come away with a rusty colored residue, you have rust. (Then go wash your hands or dispose of the paper towel in a trash bag). Rust can easily be transmitted by touch. Don't panic! It isn't going to kill or harm your plants unless you allow it to become rampant. However, you will need to implement an effective and REGULAR spray program. More about that later.
While controlling rust isn't hard if you implement a regular spray program, complete elimination is another story altogether. A spray program will kill active rust spores but it doesn't seem to affect dormant spores. I know people who have tried cutting their plants back to the crown in order to eliminate the rust but I haven't heard that this method is particularly effective and if it is a new plant just received this procedure may add to transplant and shipping shock. If you find rust on one plant, its pretty much a given that you have other plants in your garden infected so you have to cut back every lily (not to the crown but at least back to where you can effectively spray all leaves, top and bottom and get the fungicide down into the crown area), or at least all of the lilies near the infected plant. In order to have a rust-free garden in the spring and summer if you reside in more northern areas (7A and above) where rust does not over-winter, you can resort to only bringing new plants into your garden in the fall where your winter will kill any rust spores they may bring with them. Bringing in plants from another rust free-garden in the spring is possible but they are difficult to truly find. You should beware of anyone who does guarantee rust-free plants unless they live in an area where rust does not overwinter (7A and above) and they have no new plants received from areas where rust does over-winter (be sure to confirm that plants did not overwinter in a green house) between the end of winter and the shipping of your plants. Even if the new plants are quarantined in a different area of the property, if they are carrying rust spores on arrival, eventually those spores will travel to your other lilies. It may take a while but eventually they will get there. Airborne rust spores can travel for miles and rust is primarily an airborn fungus. You can try spraying only the new arrivals for rust if you have them quarantined but you must not fall down on your spray program.
People living in more southern areas where there isn't enough cold weather to kill dormant rust spores are going to have to learn to live with rust or destroy what plants they have and start over with only northern plants that have not been exposed to any plants from the south. To me this is a radical solution, bordering on hysteria. Implementing an effective spray program is a much more rational solution. I have about 250 named varieties and several thousand seedlings and I can spray every lily in about 30 minutes using a simple dial type hose-end sprayer! And it doesn't have to be outrageously expensive either. However, there are a few key rules to live by when administering your spray program. The number one rule is to NEVER spray a thirsty plant! Water the day before you need to spray. Secondly you must spray on a regular basis. If you don't, you are pretty much wasting your time. You will start to visible active rust again. You also need to rotate your sprays. I like to use three different products (although two is acceptable), at least one of which is a systemic spray. I personally use two systemics and one non-systemic (non-systemics tend to be cheaper). Heritage and Banner Maxx are systemics that are very effective on daylily rust but the they have to be ought in large quantities so the price can be prohibitive to any number of small growers. A product called Compass has the same active ingregient as Heritage but it can be purchased in smaller quanitities as a granular powder and is highly concentrated. For smaller gardens it is ideal. The current market equivalent of Daconil (chlorothalonil) now available as a systemic, Mancozeb or other manganese sulphate products, and products with azoxystrobin or triadimefon as an active ingredient are also effective and not quite as pricey. A bio-fungicide called K-Phite has shown promise as a rotation partner in a recent LSU study. Unfortunately no other bio-fungicides used in the sudy proved at all effective against daylily rust.
When I begin my spray program each year (I do not spray for rust between October and June of the following year unless I see active rust on a plant. It doesn't usually raise its ugly head until mid-July although I do keep a close eye on new arrivals because they do sometimes show rust shortly after arrival and they are sprayed immediately and thoroughly with a systemic), I spray twice a week for the first two weeks if I see active rust. If not, I just spray once a week for 6 weeks and then back off to 10 day intervals until I am done for the year. It is best to spray in the mornings if at all possible but not later than about 3:00 PM so that leaves may dry before sundown. Please remember not to spray or dip thirsty plants!
Cuttings from rust infected plants should be disposed of properly. It is not known how long rust spores live on or in waste plant material so its best to burn, bury or dispose of them in a garbage bag that will go to your local dump. I would not recommend their addition to your compost heap or in recyclable bags for pick-up and use by your local waste disposal service for addition to their compost facilityWQ .
If you want to research rust on the web, beware of articles that are old and outdated. Always look for a date the article was written. Articles written by professionals in 2007-2008 are likley to be far more pertinent and have more reliable up to date information than articles written from 2000 - 2006, although some archaic thinkers, especially in Maine and Massachusetts persist in telling growers to destroy their daylilies which is completely ludicrous. Daylily rust is manageable no matter where you live with just a little effort and common sense.
Barb Allen
12/3/08
