What causes the typical yellow streaks in daylily leaves? we have it bad. always did. but this year it seems to be worse. is it weather related? fungal? is it a soil issue? we have a dozen daylilies and all of them get it every year. this year seems to be worse than most though. thoughts?

Does it look like this?:

http://hyg.ipm.illinois.edu/ar...
http://www.daylilies.org/ahs_d...

Nitrogen deficiency could also look similar (on the lower leaves first). Here's a pic on corn for example:
http://plant-pest-advisory.rut...

If it doesn't look like any of the above, can you post a picture?

yep. along with the wilting and turning brown... its bad this year. im sure non stop rain isn't helping, whatever it is...

Well the first two links are for a common fungal disease of daylilies, "leaf streak". The fungus is a black yeast, Aureobasidium microstictum, and most likely needs an injury of some kind to infect the plant. There is more info on how to ID it, and which fungicides are effective to treat it (if you wish to) on the AHS page (the second link I gave), see the two PDF links at the bottom of that page. There are differences in cultivar susceptibility to leaf streak disease, some being more resistant than others.

If it could be nitrogen deficiency then you'd obviously need to give them some N. How likely is it that they are short of nitrogen? If it is unlikely then it would more likely suggest leaf streak. It's obviously not drought, which can also look like leaf streak!

I doubt its a lack of Nitrogen. we use diluted 5-1-1 fish emulsion regularly. the foliage that ISN'T effected is stunning. nice and green, thick, and lots of it! we just got our first scapes showing last week im assuming the damage you speak of, in order for the fungus to get in is caused by either slugs or possibly cutworms...? which are in abundance this year due to our record setting warm winter a few months ago...

thanks for the input!

I had a lot of yellow streaked leaves on my daylilies this year (had more daylilies this year) and I thought it was all leaf streak. But I started pulling the yellow leaves and the ones with the most leafminer damage. Now as the season has progressed it seems that at least some of the yellow streaked leaves might have just been naturally aging leaves. I pull a hand full and sometimes two, when I go to the garden every morning while I am dead heading. I notice that some varieties are much worse in showing the broad yellow streaks in the leaves ( Flore Pleno and Baja) are two that I seem to pull the most yellow leaves off of (once again I have more of these than any other plants also).
Early in the season I was very concerned about pulling so many leaves off the plants, but they seem to have responded well and I have not sprayed this year. Now it seems I go through longer periods without having to pull so many leaves.

Jason, it could be something like weather damage (freezing, hail, wind) that lets the leaf streak fungus in, or some small pest like thrips or spider mites.

As Larry, said, there is also natural aging, a leaf doesn't last forever (although I wouldn't expect them to do that en masse very early in the season). Leaves may turn yellow as the plant retrieves nutrients from the dying leaf (which is also similar to what happens in nitrogen deficiency - because plants can move nitrogen around to where it's needed, if it is in short supply it may move it from the older leaves to the newer emerging ones, hence the yellowing appears on the oldest leaves first as the N is translocated).

After flowering some daylilies get pretty ratty looking as well. Diagnosing a plant problem is often a process of elimination.

I am seeing some of that on mine too, but I think it is drought conditions as the culprit. I have been trying to water regularly, but the heat dries the dirt so quickly that it seems like an endless battle to hydrate the roots. It could be lack of N, too, as so many of mine have been blooming not too long ago. I will be adding N fertilizer to them tomorrow to see if that improves their appearance. Does epsom salt help, too?

This spring I have some pale leaves and they all have sunk during the winter and are too deep.

I would be careful with N if the soil is still dry and the weather hot as in that situation you're more likely to get fertilizer burn and the salts can make it harder for the plants to take up water. Epsom salts (magnesium sulfate) isn't necessary unless you have low magnesium. I don't think I would add that in dry conditions either. You're more likely to have low magnesium on an acidic soil and there are better, longer term, ways of dealing with it in that situation than Epsom salts.

Slow-release fertilizer pellets? Would that be safe to use in the Summer months?

Becky - if you're thinking about using slow release pellets in a hot, dry environment such as yours, then might I recommend something organic. this will virtually eliminate the threat of burning the roots. even better in my opinion, and much easier to apply as well, a diluted organic liquid fertilizer can be used while you do your regular watering. as I mentioned above, we use organic 5-1-1 liquid fish, as well as 0-5-5 liquid phosphate. both diluted to about 25% and used as needed during our everyday watering schedule. I would wait until your daylilies are done flowering to start using any supplemental nitrogen fertilizer however. that's when the rhizomes will start storing up energy for next years growth. while we're on the subject of watering, soaker hoses work wonders for getting down to the roots, if that's something you're having trouble with as you mentioned. we use them for 90% of our watering needs. then we apply our diluted liquid fish by hand as needed. seems to work very well. although admittedly we use it mostly in our many shade/hosta gardens.

Jason - Thank you for all your very helpful advice. I still have quite a few daylilies that have not bloomed yet. In March (Spring here), I added time-released fertilizer to all my daylily beds. But that fertilizer is probably gone by now, so I want to get blooms from the ones that may be mid-season and late-season. All of mine are hybrids and most are blooming for the first time this year. I have 3 raised beds in partial shade which they all look great! There is one raised 3-tiered bed full of seedlings as well as all along my front garden where many many more seedlings are. Quite a few have put up scapes and some are reblooming currently. But some have yet to bloom and I am thinking they may be late-season bloomers. I think the fertilizer helped to get them to bloom this year.

I do use a soaker hose along my entire front garden border. And the rest of the daylily gardens have micro-irrigation in each bed. The partial shade daylilies have the best looking folliage of all of my daylilies. I think the intense heat and sun literally fries some of the full sun daylily leaves. I can actually feel what may be a 10 degree difference in the partial shade gardens vs the full sun. It is brutally hot here this time of year up until about the end of October. Rainfall is also needed. Rainy season is in June and July typically. So I am hoping that if I use a time-released fertilizer and then the rains start coming each afternoon, then that will promote the rest of the daylilies to bloom and maybe get some more reblooms. What do you think?

soaker hoses are great aren't they? we have several of them on timers depending on whether or not they lay in a full sun bed or in a shade garden. im not sure about your daylilies reblooming however. I suppose you may get lucky if you have a reblooming hybrid of some kind. ours never rebloom regardless. its hard to offer advice for someone with completely different weather conditions. its 50 degrees and raining right now in my area. and we haven't even begun to worry about watering yet. most of our summer flowering plants are just now starting to get their buds. as a matter offact, we have a dozen daylilies and only one has any signs of having scapes so far! but it sounds like you've got a handle on it pretty well. the part sun/part shade idea is a good one. especially in scorching conditions. our daylilies only get 3.5 hours of afternoon sun- that's it. and they bloom great for us! so it should work well for you too.

Jason - Ugh! You have my utmost sympathy with such cool weather when it is almost June. My daylilies started blooming in early April and have been going strong ever since until this heat hit. Though it could be that the wave of early-mid season bloomers are a large number of the seedlings. I do have some rebloomers currently. This is the first year I've seen reblooms from any of my seedlings. I really think the time-released fertilizer had something to do with that. But when I say I don't have many blooming currently, that is not entirely true. I probably have 30 plants blooming today, so I do have daylilies blooming in the partial shade and full sun garden beds. Just not in great numbers. I have over 300 seedlings, so 30 blooming is only 10% of the plants blooming at this time. I will say though that using the time-release fertilizer this year has had a noticeable effect. Far more blooms than previous years. Something to be said for time-released fertilizer.

Is it thrips...they make these little yellow/orange lines....the leaves will then turn brown and fall off

Pam - apparently the thrips had been in heavy training over the winter...