Avoid over-head irrigation. In the fall, remove dead foliage from around the base of the plants and dispose of the clippings, as the fungus will over-winter on senesced foliage, and spores will be produced the next spring to infect new leaves. Examples of resistant daylily cultivars include: Betty Bennet, Edna Spalding, Ella Pettigrew, Globe Trotter, Nancy Hicks, Pink Superior, Ron Rousseau, Sudie, Tropical Tones, Upper Room, and Winsome Lady.

To control leaf streak the fungicide thiophanate-methyl or myclobutanil may be applied to slow disease development and to protect susceptible new growth from infection. Begin sprays as new growth appears. Make 3 or 4 applications at 2-week intervals. If you use fungicides of course.

Thanks to everyone! I am not panicking I already thought about it. I'm not irrigating much, here the weather is hot and dry. I am removing damaged leaves and toss them immediately. I use fungicides, I don't know if the one I have is the one mentioned here.

We don't know for sure your problem is leaf streak, not all of it looks like leaf streak and if only the odd leaf here and there is affected it's not really worth using a fungicide.

In my opinion, and I am not a botanist or expert, I have a problem with the no overhead watering. Most plants are designed for regular rain. Not trying to be smart, but isn't that overhead watering that can occur at any hour of the day? Overhead watering can knock aphids off, keeps spider mites at bay, and in hot climates can cool the whole plant down. Keeping pests controlled and off plants, (which overhead watering can help do) limits the spread of disease. I think we could all come up with a few more reasons for the benefit of overhead watering. This is just my personal rant and there is more frustration here for plant problems that seem to be more prevalent since tissue culturing.

Daniel is being very nice and helpful with all of his suggestions. Daniel, I understand that you are just relaying the industry standard about watering. I appreciate that you gave multiple ways of control, makes us all think of our garden practices. Thank you for taking the time to put that together! Many blessings to you Daniel!

I agree with Sue. That is also good advice! Many blessings to you Sue!
God bless our efforts, plants, and America! And for those from other countries may God bless your country! Happy fourth of July!

Where overhead watering can be a problem is with fungal diseases that require a wet leaf before they can infect a plant. To give an example, daylily rust spores cannot germinate to infect a leaf unless that leaf has water on it for several hours. So if you want, or prefer, to water overhead then do it early morning - the plants are often already wet from dew, and the leaves will soon dry quickly with the sun. That reduces the number of hours the leaves are wet. Watering late in the day would be the worst time. The leaves will potentially not get dry until the next morning. You can totally cover a daylily leaf with rust spores but if you can keep it dry it will not get rust. Of course that's impossible outdoors but in a house the leaves would have to be misted to provide wet leaves for long enough to enable spore germination.

A downside to using fungicides is that they can increase pest problems by killing the fungal diseases that attack and kill the pest, so the fungal problem would have to outweigh the potential for pest problems. Also, going back to leaf streak, that fungus infects via wounds (unlike daylily rust which enters through stomata), so can be related to pest or weather damage.

Many thanks to everyone for your precious advices and points of view.
I tend to believe it's leaf streak and not simply sun scorching. It started to happen to a couple of seedling I planted in the ground past week, They were in pots and no signs of disease but since I moved them in the garden the small leaves are starting to show the same signs. The pots got even more sun because I always moved to be always in the sun, while plants in the ground can't move, and get less hours of sun.
The fungicide I have doesn't have the ingredients mentioned by Daniel. Here the weather is really dry except for a once a week watering by hand, and yes I watered overhead to clean some plants from spider mites. These can be the pest that opened the way to leaf streak.

Good luck Sabrina, I hope whatever it is either just goes away or you can manage to get it under control

I took some other pics. Ugly leaves and the lateral leaves (bracts) are all dry. leaves on a proliferation are staring to have those dark yellow streaks.

I may be totally wrong, but I think those are just old leaves and I pull them off. It may be some leaf streak but still I just pull them off. I end up with large buckets full of deadheaded blooms and dying leaves almost every morning. I keep reading the way to treat diseased leaves is to pull them off, but I also read that it is taking away the energy of the plant when you pull the leaves. But, when I did not pull the leaves and the old brown scapes the plants looked totally awful. Then the other day I watched a video that reinforced the idea of pulling off the dying old leaves. It stated that the plant would shed the leaves on its own, but it would take a period of at least two weeks for the plant to look green and fresh again and by pulling them off as they turned brown or even yellow you could avoid mostly avoid that two week period. Now it may be that my plants will suffer in the future and become weaker, but I will say my garden looks so much better overall that it is worth it to have the plants look so much better. I just could not stand having all those dying brown and yellow leaves showing along with the brown dying scapes. I am going to harvest a lot of my proliferations today, so I can let the dying scapes go ahead and finish up so I can pull them . The scapes with seed pods and proliferations turn brown at the tops but stay green for a long period and I don't like that look.
Here is the video I watched, and I use a bucket like that big black one in the video and I often pull two or three bucket fulls of old scapes and leaves in a single morning.
https://www.youtube.com/watch?...

Thank you Larry @Seedfork, I knew that video!
I also pull the really yellow leaves. But not scapes. There was a discussion on here and many said that the DLs can take back some energy from dead flowers and dying scapes.. so I just pull and if they come off it's ok, otherwise I let them there.
What is worrying me are those yellow/brown streaks going along sides of leaves, there's one proliferation that's doing it too.
Please, can you explain me how do you harvest proliferations and how do you treat them? I have a big one you can see here The thread "Is this a proliferation?" in Daylilies forum

I know the garden seems more ugly with browning things here and there, but still can't decide what's beneficial to the plants!

cut the stem about 2 inches below the proliferation once roots are showing and stick it in a pot with good potting mix. If roots don't appear wait until the scape starts turning brown and harvest the same way before the proliferation turns brown. cut the foliage back as soon as the proliferation is harvested so the plant does not die from whats known as transpiration. Dust the base of your proliferation with rooting hormone which will encourage more roots plus has a fungicide to protect the proliferation . Never let the planting medium dry out or you could loose it. keep the medium moist but not soggy. Also remember to label your proliferation once it's harvested. Others may want to add some things I may have forgot to mention but that's about it. once potted wait about a month or 2 and your new plant should be able to be transplanted in the garden or traded for other plant material. Good luck Sabrina

@cybersix,
I just posted over in the other thread "Is this a proliferation". I included photos of the ones I harvested.

Thank you Daniel and Larry.

you are very welcome

cybersix said:I took some other pics. Ugly leaves and the lateral leaves (bracts) are all dry. leaves on a proliferation are staring to have those dark yellow streaks.

http://www.daylilies.org/ahs_d...

Judy, I'm pretty sure it's leaf streak. I also found tiny black spots, I read that is caused by the fungus.
But I can't buy the specific fungicide it requires a sort of license and I'm not a pro, I'm just a house gardener.

I keep on removing infected leaves, they are so many. I don't know how to control it. I'm not watering and it's not raining so I hope it will help against spreading this fungus.

I went out and took off all the leaves that had suspicious signs, but I found some spider mites and their marks on almost every leaf. So I read more about spider mites and the symptoms could be very well due to them. I had a bad infestaction on mainly two plants, one of them has the drying buds I wrote about in another thread. And this could be a spider damage too.
I cleaned all that I could, now the sun is hitting the garden so later this evening I will spray an insecticide for spider mites. I would like to water, it's not raining, but still have the doubt about leaf streaks. So I can't decide what to, but probably will go ahead with the spray. Since I have to pipe water I'll end wetting leaves too, and in case of leaf streak it's not reccomended.

Being dry could be contributing to the problem so if they need water they should be watered regardless of a possible fungal disease.

Yes Sue, I watered and tried to water the ground only. I will keep an eye on how the things go. Many thanks!

I had to scroll back to see if I'd started this thread and forgotten to check it This has been an incredibly bad year for fungal leaf streak, not just in one bed but in all the beds around the house. We had a long, wet, cool spring which is when the problem started. Then within maybe two weeks the weather transitioned to hot, humid, and dry. (Also had a lot of problems early on with black spot on roses but began using the drench version of Bayer 3-in 1 Rose Care which has slowed it down). Foliage has been ugly, ugly, ugly. However, it hasn't stopped the blooms, almost all plants being unusually prolific producing scapes. Even reblooming has been heavier than usual. So now the main blooming season is passing and the leaves are browning and drying out. I'm working at getting the beds thoroughly cleaned out but quite a few plants are looking kind of 'spare' of leaves, some almost disappearing entirely (though I'm beginning to notice new fans popping up). I'm thinking it's probably time for a light application of fertilizer after the heavy blooming season and spraying the clean plants with fungicide when the temperatures moderate again late in the summer. So has anyone else experienced more than usual leaf streak this year???

There definitely seem to be certain cultivars that are more resistant to the fungus than others. For example, "Prairie Blossom" has had a few streaks but considering the plants around it seem to have it pretty heavily, the plants are looking really nice and are even beginning to put up new scapes for a rebloom cycle. On the other hand, "Mexican Maiden", about 10 feet away, every plant was heavily infected and after the blooms finished, some of the plants have almost disappeared when the dried foliage has been removed (though the worst are beginning to show new leaves popping out of the ground). Both cultivars are in full sun and I water both the same way. I need to take a notebook out and begin noting the cultivars that seem to be resisting the fungus and which have it bad. One think I have noticed, the ones with the small, grass-like leaves has not been showing it as much as the broad-leaf varieties. Don't know if there's a connection there but something to watch and note in the future.