sooby said:Peter, daylily rust doesn't overwinter on Patrinia, it overwinters as teliospores, the black winter spores, (not the orange summer spores except in very mild winter climates) on dead daylily leaves and then transfers to Patrinia in spring. Of course an existing infection can also overwinter as mycelium (fungal threads) inside any daylily leaves that can stay green and alive.

The spores are are just the reproductive units, like a plant seed, the actual fungal body itself lives inside the leaves feeding on nutrients from the plant's internal cells.

Heritage as a soil drench was found to control daylily rust for 120 days with a single application, a result that was comparable to 14-day interval foliar sprays, see Dong et al, 2013 : http://apsjournals.apsnet.org/...

Maurice, yes to 1 although technically it is not the teliospores themselves that affect Patrinia but their next spore stage but it amounts to the same thing.

For 2, daylily rust urediospores (the orange ones) can be deep frozen for use in lab tests at temperatures far colder than would occur in nature. So it is not cold alone that kills them outdoors but some combination possibly combining time, light intensity, moisture and temperature.

For 3 yes if the infected leaf dies, the mycelium inside it (the body of the fungus) dies too. In some rusts the mycelium can be killed by temperatures above that which would kill the leaves but nobody has tested this for daylily rust. So to be safe we assume that the leaves need to actually be killed to kill the rust. It is possible that the fungus could be killed a little before the temperature goes low enough to kill the leaf.

Thank you for the correction, I had that backwards.

As for heritage as a drench at a application rate of 0.10oz per gallon. You'd get 40 gallons Of mix for roughly 90-100 dollars.

I doubt anyone could afford that...

I also don't like this part.

"The three fungicides did not affect microbial
biomass or bacterial community structure in either soil but did affect some protozoa and fungi (3). Adetutu et al. (1) observed that over 60% of the azoxystrobin in soils was degraded over 21 days
and that, under certain conditions, the fungicide could modify fungal
communities. The half-life of azoxystrobin in soils is 7 to 56
days (24), and yet environmental fate studies indicate that azoxystrobin
should be moderately persistent, with a half-life of 72 to
164 days (25). Obviously, more research is needed to better
understand the impact of fungicides on the soil microbiota. "

@profesora, Gerry, did rust appear on your new purchases this year? Were they late summer purchases or early spring purchases? How long after you planted the new daylilies did you notice rust appearing on your plants?

Nysbadmk8 said:

As for heritage as a drench at a application rate of 0.10oz per gallon. You'd get 40 gallons Of mix for roughly 90-100 dollars.

I doubt anyone could afford that...

I didn't work out the cost so I'll take your word for it I know the strobilurins are expensive (I think Compass is the least so). But I was responding to a question about what I interpreted as an eradication attempt related to the question of whether one should spray both before and after when cutting back. In that case the cost of a single soil drench before cutting back might be justified if it enabled rust to be eradicated from the garden altogether, and that's definitely an if but so is foliar spraying for that purpose.

That would also have to assume that the garden in question is not in an area where rust is endemic so that it would simply blow back in on the wind, and that the gardener isn't going to buy any more plants that are carrying rust.

I notice you are rotating two strobilurins in a tank mix with two different contacts. I'm wondering why go to the expense of two different strobilurins?

One other thing to bear in mind with daylily rust is that it can have a long latent period, that is it can be present in the plants but not show any external spots, for at least seven weeks or more under certain conditions.

Karen, all the rust were on plants that arrived very late in September 2015, and they overwintered in the greenhouse. I also had seedlings in the greenhouse that were affected. Of course, this summer they were taken outside, and they were cut back, sprayed and planted. I did notice that some rust was evident late summer, but very little.


I have less than two dozen newly arrived, potted daylilies that are still outside with the intention of placing them in the greenhouse after they go dormant. Here all daylilies go dormant.

Now these plants are a new experiment. I will start to document my observations, and write an article about an year from now.

I am in zone 5b, but my property is on a low land where it experiences cooler temperatures all through the year. Summers are great in the shade garden because it is at least 10° cooler. A few zone 5 plants do not survive winters in the shade garden. Zone 5 Japanese maples do not survive. I have tried many times. It is just much colder there in the winter.

sooby said:

I didn't work out the cost so I'll take your word for it I know the strobilurins are expensive (I think Compass is the least so). But I was responding to a question about what I interpreted as an eradication attempt related to the question of whether one should spray both before and after when cutting back. In that case the cost of a single soil drench before cutting back might be justified if it enabled rust to be eradicated from the garden altogether, and that's definitely an if but so is foliar spraying for that purpose.

That would also have to assume that the garden in question is not in an area where rust is endemic so that it would simply blow back in on the wind, and that the gardener isn't going to buy any more plants that are carrying rust.

I notice you are rotating two strobilurins in a tank mix with two different contacts. I'm wondering why go to the expense of two different strobilurins?

One other thing to bear in mind with daylily rust is that it can have a long latent period, that is it can be present in the plants but not show any external spots, for at least seven weeks or more under certain conditions.

I'm using two for rotation as both products recommend it.

Also Cabrio is far and away less expensive at roughly 220 dollars for 5lbs compared to 4oz of Heritage at 100 dollars.

I would also like to acquire "headline" but its only sold in 2.5 gallon containers at a cost of 800-900 dollars and its very hard to find. Its bill waldrops goto fungicide in his greenhouse operation which is far superior to my own.

I also had no rust appear till the last day I looked which was Nov 16-17th.. with Multiple exterior freezes the foliage is now dying. That puts it at roughly 6/6.5 weeks

Nysbadmk8 said:

I'm using two for rotation as both products recommend it.

The labels don't recommend rotating a strobilurin with another strobilurin though, which is what both Heritage and Cabrio/Headline/Insignia are. For example the Heritage label says "since Heritage fungicide is a strobilurin fungicide, avoid alternation with other strobilurins" . This is under Resistance Management on the label.

Thanks Gerry! I am interested to find out how long does it take for the dormant spores to appear as rust from infected plants. I have found rust on a few plants purchased from warm areas. I stripped off the infected parts and sprayed the rest of the plants and then planted them. I have not seen rust outbreak but I wonder how long will it take for the rust to appear if my treatment does not kill all of the spores.

Karen, I'm not sure I fully understand the question about dormant spores appearing? Rust lives invisibly inside the plant as fungal threads. Eventually these produce reproductive units called spores that you can see from the outside of the plant. This is similar to a plant producing seeds. In the case of rust, the plant is the fungus and the spores are the seeds.

Because the fungus lives inside the plant, you need for these fungal threads to die, it isn't enough to kill the spores on the outside of the plant if there is fungus inside the plant that has not yet shown itself by producing spores.

It has not been determined exactly how long the fungus can stay alive inside leaves without sporulating (producing spores on the outside of the leaf or scape). The only thing we know from a research observation is that it can be seven weeks or longer between exposure to spores and the appearance of the next cycle of spores.

There's more detailed info on this here:
http://web.ncf.ca/ah748/latent...

I'm not sure if this answers your question?

sooby said:

It has not been determined exactly how long the fungus can stay alive inside leaves without sporulating (producing spores on the outside of the leaf or scape). The only thing we know from a research observation is that it can be seven weeks or longer between exposure to spores and the appearance of the next cycle of spores.

There's more detailed info on this here:
http://web.ncf.ca/ah748/latent...

I'm not sure if this answers your question?

Thank you, Sue! Yes, you answer my question. It may take the fungus that lives inside the fungal threads between 2 to 7+ weeks to appear as rust spores on the foliage if the threads are not killed. If I don't see an appearance of spores for 7+ weeks during the growing season on new daylilies, can I assume that the daylilies are free of rust??

I planted 30 new daylilies this September. Some of these daylilies had rust in the inner leaves when I stripped them down. I stripped and threw all the infected out and sprayed the whole plant with fungicide. I have been watching them these past 2 months for any appearance of rust. I did not see any but how can I be sure that all the threads/spores had been killed. Can the threads/spores survive my cold winter so that the fungus start to germinate the following year when the conditions for rust are favorable?

sooby said:Karen, I'm not sure I fully understand the question about dormant spores appearing? Rust lives invisibly inside the plant as fungal threads. Eventually these produce reproductive units called spores that you can see from the outside of the plant. This is similar to a plant producing seeds. In the case of rust, the plant is the fungus and the spores are the seeds.

Because the fungus lives inside the plant, you need for these fungal threads to die, it isn't enough to kill the spores on the outside of the plant if there is fungus inside the plant that has not yet shown itself by producing spores.

It has not been determined exactly how long the fungus can stay alive inside leaves without sporulating (producing spores on the outside of the leaf or scape). The only thing we know from a research observation is that it can be seven weeks or longer between exposure to spores and the appearance of the next cycle of spores.

There's more detailed info on this here:
http://web.ncf.ca/ah748/latent...

I'm not sure if this answers your question?

Hmm, thanks for that Info I was under the impression the MOA was different between those two Group 11's.

Karen, the problem with the 7+ weeks is that we don't know how many + weeks it takes. If all your daylilies die back to the ground for the winter then rust can't survive. If you have some daylilies that stay green even partly then we can't rule it out although the belief is that it doesn't normally winter over in zones colder than 7, and not always even in 7 depending on the winter. Since you're zone 6b the summer spores are not likely to survive your winter. The fungal threads could do if the daylily leaves on all infected daylilies are not killed back to the ground but there haven't been any definite reports of daylily rust overwintering in zone 6 that I'm aware of. In every case I've heard of it could have been brought in on new plants. In one or two other cases it turned out not to even be daylily rust, just a lookalike.

I'm so confused now! I never had rust until this year after I purchase a bunch online (no clue which batch it came in) so I'm hoping with removing all of the foliage and with our Iowa winters, that I won't have to treat it. But if I did, would I treat it this Fall yet and with what? No greenhouse, just outdoors.

Ginny, what exactly is confusing you, maybe we can help? Daylily rust should die out naturally in Zone 5 outdoors.

Nysbadmk8 said:

Hmm, thanks for that Info I was under the impression the MOA was different between those two Group 11's.

Unfortunately not. You might find this article useful, from the American Phytopathological Society about the QoI (strobilurin) fungicides. A quote:

"All QoI fungicides share a common biochemical mode of action: they all interfere with energy production in the fungal cell. To be precise, they block electron transfer at the site of quinol oxidation (the Qo site) in the cytochrome bc1 complex, thus preventing ATP formation. The preceding sentence may "seem like Greek" to even the most knowledgeable crop consultant, but it contains an important point-that the mode of action of the QoI fungicides is highly specific. Of the millions of biochemical reactions that occur in the fungal cell, these fungicides interfere with just one, very specific biochemical site."

From: QoI (Strobilurin) Fungicides: Benefits and Risks:
http://www.apsnet.org/edcenter...

Some of my daylilies (even after the freezing weather) have not died back yet. I have so many new ones this year I'm assuming that they will all die back, but maybe not do it while I can still get outside to remove the leaves. Should I go ahead and cut back the green leaves now along with pulling the dead foilage, and do I need to put a fungicide on them this Fall just to be sure I don't end up with rust in the Spring? Several of the plants have so much rust it's pathetic looking. Before I introduce any more new ones into the garden I'll make sure they are rust free in the future hopefully. I'm just trying to decide if I still need to apply a fungicide this Fall so I can order it now. If it weren't for the fact that I'll be on a garden tour next summer I wouldn't worry about it so much. Sorry Also, can rust live on garden tools?

If they typically all die back you don't even need to remove the leaves. It would not be a bad idea to do so if you think any might remain green at the base right through winter otherwise - removing the leaves will allow the cold to penetrate more. I would be very, very surprised if daylily rust survived the winter in Zone 5a Iowa. It would change everything that we've learned in the past sixteen years since daylily rust first arrived in North America.

You can't make sure any new daylily is rust free in advance, even if a new plant has no visible pustules it does not guarantee it isn't carrying rust internally. Some people get around this by buying from sellers in non-rust areas - there's a small risk with that that the sellers may have themselves brought rust in on new plants before they shipped yours.

In theory spores could stay alive on garden tools but not likely for very long. Not likely for long enough to re-infect the garden next year.

sooby said:

Unfortunately not. You might find this article useful, from the American Phytopathological Society about the QoI (strobilurin) fungicides. A quote:

"All QoI fungicides share a common biochemical mode of action: they all interfere with energy production in the fungal cell. To be precise, they block electron transfer at the site of quinol oxidation (the Qo site) in the cytochrome bc1 complex, thus preventing ATP formation. The preceding sentence may "seem like Greek" to even the most knowledgeable crop consultant, but it contains an important point-that the mode of action of the QoI fungicides is highly specific. Of the millions of biochemical reactions that occur in the fungal cell, these fungicides interfere with just one, very specific biochemical site."

From: QoI (Strobilurin) Fungicides: Benefits and Risks:
http://www.apsnet.org/edcenter...

Any good suggestions for rotation between the two?

I really appreciate the explanation

Nysbadmk8 said:

Any good suggestions for rotation between the two?

Not from personal experience. When I had rust here I had deliberately introduced it and wanted to keep it alive for observation and tests I assume you want to keep using both strobilurins because you have some to use up? The tank mixes with the two contacts should help from a resistance point of view. If you wanted to alternate with another systemic there are some suggestions in this AHS article:

http://www.daylilies.org/RustR...