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Daylily Rust

Lately I’ve noticed that quite a bit of attention has been given to a new nemesis on the American gardening scene – daylily rust. This fungus is indeed a formidable foe simply because not much is known about it.

Daylily rust, Puccinia hemerocallidis, is identified by the orange powder spots that appear on the undersides of leaves and the scapes of infected plants. Other daylily disorders such as leaf streak and spring sickness may resemble the early stages of daylily rust.

A simple test is to take a clean, white tissue and run it over the leaf’s surface. If it comes back covered in an orange, dusty substance you are probably dealing with rust. Visit the American Hemerocallis Society’s “Daylily Dictionary” for images of daylily rust.

If you are still unsure if your plants are infected you can always send a leaf sample to be tested. Check with your local cooperative extension service for a diagnostic laboratory in your area.

Because daylily rust is fairly new to this country, methods of prevention and treatment are still being tested. Here are a few tips that you can follow that might help.

When you bring new daylilies into your garden, isolate them from your other plants for a season. They may be infected without showing any symptoms. Keep them quarantined for as long as six months. If your new plants arrived bare root, pot them up before you set them aside.

Patrinia is another native Asian plant that is not only susceptible to this disease, but also plays winter host to the spores. In spite of the frustration it produces, I find this to be a rather interesting relationship. Certain rust spores subsist through the winter on dead daylily leaves. In the spring they re-generate as a spore that does not affect daylilies but does harm patrinia. Borne by the wind they infect any nearby patrinia plants and then reproduce in a form that can once again attack daylilies.

One method of control is to strip the outer leaves of your new plants, cut the remainder down to about 1 – 2 inches above the crown (where the leaves connect with the roots), and saturate with a fungicide before planting. Be aware that this practice may cause even more stress to a plant already weakened by transplanting and shipping. For step by step instructions with images visit http://www.ncf.ca/~ah748/newplants.html

If you find that your established daylilies are inflicted with daylily rust, simply cut back both the diseased and healthy foliage to the ground and destroy the infected leaves. Do not add these leaves to your compost bin. You can spray the leaves before you do this to limit the spread of the spores and then spray the ground around the plant after the leaves have been removed.

When using a fungicide to treat daylily rust, alternate between a systemic and a protectant type.

As with other fungus, daylily rust thrives in moisture. Use soaker hoses rather than overhead watering systems and water in the morning rather than late in the day or at night. This will cut down on the amount of time that the leaves remain wet.