Looking outside at the snow and ice still on the ground I am wondering if this might be a good year for daylily growers in the south, one that might have a lot less rust in the garden. I don't have any expensive daylilies, and not that many varieties, still I hate to see rust on the leaves, so I am hoping that with all the cold weather we are having this year I may see very little rust on my plants.

I was hoping for the same thing in my zone 6b garden. It is a wait and see process, but I am keeping my fingers crossed. We have had many days of below freezing temps. Today was one of the few in January that actually felt good and I didn't have to warm the car up before going to work

Below are the temperatures that killed rust dead in its tracks,
but actually it died during the autumn frosts before the winter temps kicked in.
That is when the summer spores changed to winter spores whereby
they cannot reinfect the next spring because they need a separate
plant host to do so. This is what I observed in my garden. In other climates,
rust may react differently. I was surprised by how much a small amount of
hard frost affected rust. Rust does not worry me anymore due to that
experience.

In December we had 16 lows below 32* with the lowest low for 1 night at 18*
In January we had 18 lows below 32* with the lowest low for 1 night at 18*
In February we had 19 lows below 32* with the lowest low for 1 night at15*
In March we had 16 lows below 32* with the lowest low for 1 night at 16*

So a total of 69 nights below 32* definitely killed rust here. Many low temps fell
in the 25 to 31 range.

We have had more cold days this year than I can remember (below 32) so it will be interesting to see what happens about September, that's when we normally see the first rust around here. Yesterday I started cutting the dead foliage from the potted plants to try and prevent crown rot. All that mush laying on top of the crown can not be good for them after thawing out, most will be completely thawed today and start growing again. There's about 2-3 inch's of green foliage under all the mush. Only the evergreens have been effected by this cold, the sev and dormant's look great. A good thing about this year, I can tell which seedlings are sev and dormant, they don't all look like ev.

Thanks for that reminder, I need to do the same for my evergreens, they look so pathetic right now, looks like they melted.

I was surprised to see Rust did not appear until September for Fred, I get it very early in the year. The high temps. tend to slow it down, then later in the year it returns, but not as bad normally. I did go out and clean up all my Evergreen daylilies, they look much better now !

I will be cutting the foliage from mine tomorrow and I plan to spray Banrot and Kphite.

Seedfork: About your question...... it really depends, in your area it may have killed it but I know here (this area) it didn't. It may have lessened it some but as long as there is green on the daylily there is a chance the rust is still there. Rust begins in the inside of the plant and lives in the green of the foliage so if the plant is already infected with rust inside then if there is any green at all left on a plant throughout the winter then rust can survive; it will just need the right conditions to pop up.

I found one site on the web that rates the daylilies they sell for rust, at first I thought that was a great idea. Then they mentioned that the amount of sun they were grown in had a great effect on the daylilies as far as rust contamination ,(as shade of a garage or tree, compared to mostly sun). None were immune, but the ones that got the best rating were A+, the worst was F. Yes, I thought that was a great idea, then it hit me that would have to be a very local rating system because of so many differing factors. I have seen a few short lists of varieties that were suppose to be resistant, but that may not even be true for different locations. I had even considered shopping only for very resistant varieties, but it seems now that would be impractical. It appears right now it is just a matter of trial and error, a plant very resistant in one area might be very prone to rust in another. Am I understanding this correctly?

From various conversations I had with growers the one year I had rust, there is a theory out there that says that just freezing temperatures (32) are not enough. The temperature must be below 18 degrees for 2-3 days in order to kill the rust. In my case this proved to be true, and I had no rust the year following a rust outbreak after temperatures went down to that mark and held for 2 days (aside from other cold days that just weren't as low as 18)......Michele makes an excellent point too. As long as there is even an inch or so of green down near the crown of an infected dayliliy, the rust spores could conceivably over winter. I still isolated those daylilies that were heavily infected with rust that retained even a smidgeon of green over winter until another growing season elapsed. As it turned out there was no new rust on even those.....I think caution is always wise when bringing in any new daylily from anywhere, but the marginal southern zones (7b-8) may have experienced enough cold this year to have a good reduction in rust, at least in the early spring. Order and plant early would be my advice. This will lessen the risk of receiving rusty plants as the gardening year progresses......Maryl

Maryl, I had green leaves as well that did not show up with any
rust, but different zones tend to be, well, different, so I agree
best to quarantine any new plants coming in. I do that as well.

Now if this winter's temps don't cause me to become literally
sick due to loss, I'll be so relieved, and have far more faith in
these plants. We have had some that survived laying on top
of the soil. A few that I didn't get around to discarding.

I have heard the same information concerning rust that Meryl has - - that the temperature must be well below 32 degrees for a period of time before the rust spores are killed. In my case here in eastern Georgia, I would assume that once I get the dead leaves off the plants, there will still be some rust remaining. I had started removing leaves before this last wintery blast, so I will have to start over with the ones I had already done. If there are a couple of days with decent temperatures (55 F or better) and no rain (like today) I will start with my first spraying so maybe I can reduce the likelihood of an early outbreak. Fred is right, a couple of days of moderate temperature and the evergreens will start growing again. Rust doesn't reproduce well at the lower temperatures, but it can surely live through what we here in the deep south call "cold."
Larry

I went to wundergound weather and looked at the calendar for Jan. and we had a three day period of 20, 14, 17, then another four day period of 24, 19, 18, 24, that may not kill daylily rust completely for this year but with the cold so wide spread and so far down, I just can't help but have high hopes for very little rust this year. That is little rust on the plants that lived though those cold days. I do believe the great majority of them did fine.

There was an article in the Daylily Journal about daylily rust. In it the researchers indicated that they kept their spores alive for testing by keeping them in a freezer at -112F.

I don't think that cold by itself will necessarily kill daylily rust spores.

EFFICACY OF FUNGICIDE TREATMENTS FOR CONTROL OF DAYLILY RUST in the Daylily Journal, Vol. 57, pages 53-59, 2002.

The best I understand is that daylily rust spores change from summer to winter spores with the drop in temperature. Then once they change into winter spores they can't change back into summer spores with out a host plant being available (Don't remember the name off hand). So I can see they can keep the spores alive, and you are right it does not actually kill them (from what I have been able to understand) it just changes them. I am sure others can give a much better explanation.

The fungus mycelium (that is the mass of thread like parts that grows inside the daylily leaves) makes spores. It can produce either type of spore and changes from producing one type to the other. In the summer the fungus inside the infected daylily produces summer rust spores. As winter approaches it starts to produce the over-wintering spores. If the fungus survives the winter inside an evergreen daylily leaf than it can switch back to producing summer spores. The summer spores it produces do not change into winter spores that is the spores that have been produced are not changed but what spores are being produced by the fungus does change . The fungal mycelium inside the daylily can change back to producing summer spores if it survives.

Here is the best site I have found so far explaining the rust cycle: Complete with illustrations for people like me who have a hard time understanding things.

http://web.ncf.ca/ah748/diagra...

All this cold may not do rust in for the summer, but I sure hope it slows down the mosquitoes, ticks, and fleas and any other pesty pest.

Mosquitoes, ticks, and fleas, and hopefully some black widows.
Having a 'normal' winter this year, and it's c-o-l-d, so don't expect to
see any rust. However, I still watch for it, especially with new plants
coming in.