Daylily rust can be treated

By Audrey Post
MS. GROW-IT-ALL

Q: I have dwarf reblooming daylilies with numerous buds on all but two plants. Those two have a yellow scale on the underside of numerous leaves that is visible on the top, too. Until now, these have been easy-care plants. I have them planted in full sun, and I water them with a drip hose from a well when it fails to rain for a week. What do you suggest?

A: What you’re seeing might be what’s called “daylily streak,” which is a minor leaf disease causing more yellowing than most gardeners find attractive. But from your description, I think the problem is daylily rust, which is more serious.

Daylily rust is a fungus that is spread by airborne spores. It was first discovered in the U.S. in 2000 here in Florida and in Georgia. Since then, it has spread to at least 30 other states. It starts out looking like a water spot, which spreads and forms small pustule in the center, which contains powdery spores that are spread by wind or movement of the plants. To the naked eye, the foliage has yellow streaks with rust-colored spots and smears.

Take a white facial tissue and rub it across the affected area. If a yellow-orange stain appears on the tissue, that’s a sign your plant has daylily rust -- Puccinia hemerocallidis.

The rust can be treated, but it is labor intensive. First you need to carefully remove infected foliage from the garden, remembering that movement of the plant spreads the spores. Put the foliage in a plastic bag, seal it and dispose of it in the trash. Don’t compost it or burn it.

Some gardeners advise removing all the foliage from that bed to contain the fungus. When the new foliage starts to grow, apply fungicide. The standard practice has been to apply two different fungicides on an alternating schedule.

The Florida Department of Agriculture and Consumer Services’ Division of Plant Industry recommends commercial growers use two of these four fungicides: propaconizole (sold under the trade name Banner Maxx); azoxystrobin (Heritage); flutolonil (Contrast); myclobutanil (Systhane). Be sure to follow all label directions and precautions.

That said, daylily rust won’t kill your plants; they just won’t perform as well or look as good as they otherwise would. It’s your choice how much effort you want to put into protecting daylilies from this disease.

One friend dug out her entire daylily bed and replaced the plants with daylily cultivars known to be resistant to rust. Reputable growers and local nurseries know which plants are resistant. Another friend simply removes the infected foliage when she sees it and accepts the fact that she has a little rust in her daylily bed.

Unfortunately, some of our most beloved cultivars, including Stella d’Oro, have been found to be susceptible to rust. Like rose gardeners, some daylily gardeners want a particular plant badly enough to do the work required to keep it healthy.

I suggest you remove the two infected plants and see how the others in that bed fare. You can always spray later if you think you need to. To minimize spore dispersal, place an open garbage bag over the plant and pull it out by the roots, then flip the bag right side up and tie it securely. Any spores should fall to the bottom of the trash bag.