Viewing post #1031264 by sooby

You are viewing a single post made by sooby in the thread called Buying Daylilies from Southern Vendors.
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Jan 13, 2016 4:11 PM CST
Name: Sue
Ontario, Canada (Zone 4b)
Annuals Native Plants and Wildflowers Keeps Horses Dog Lover Daylilies Region: Canadian
Butterflies Birds Enjoys or suffers cold winters Garden Sages Plant Identifier
There are two separate ways daylily rust can survive (actually three but the other requires patrinia plants). You have the body of the fungus, made up of strands called mycelium, which is the parasitic part of the fungus that "steals" the plant's nutrients as it lives inside the leaves where you can't see it. Then you have the visible spores that the mycelium produces on the outside of the leaves, which are asexual reproductive units. So to think of it in equivalent terms, the fungus is like a plant and the spores are like the plant seeds. Killing seeds doesn't kill a plant.

This is all a long way of saying that focusing on the spores is not enough. Yes you can kill spores on the outside with a contact fungicide as long as that fungicide can contact all the spores. That won't do anything to the fungus that is inside the leaves waiting to sporulate (produce spores). To go after the body of the fungus inside the leaves you would need a systemic fungicide but not all of those kill the spores on the outside. You can strip the leaves with or without fungicide treatment, the link I gave above (post #1030111) illustrates a method of doing this that others have used.

Freezing of the foliage to the point where the foliage dies will kill mycelium. Freezing that doesn't kill the leaves may not kill the mycelium.. It is possible that mycelium will be killed at a higher temperature than will kill the leaves but in research on some other rusts it was found that rust mycelium could survive as much cold as the leaves could. Since we don't know which category daylily rust comes in we might assume that if the leaves survive a freeze then so could the rust inside them. A daylily can have its leaves frozen on the top but still have living green leaves at the base, and daylily leaves can survive quite a few degrees of freezing in any case.

Daylily rust spores can be deep frozen in a lab at much colder temps than they would experience outdoors, and still remain capable of causing an infection. The spores are less robust in natural conditions outdoors but even assuming they are killed you still need for the fungal mycelium inside the leaves to be killed as well to get rid of the disease.

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