Disease

Since it has rained my Iris have gotten brown spots and the tips are turning brown...and then the whole leaf will turn brown......Years past I thought I had the borer but it is still April and has been cooler than usual and I think it would be to early for the borer.....Any ideas would be helpful...

Bluepoppy, I have the same thing. It is apparently a fungus caused by water splashing off the ground onto the leaves. I had a very slight case of it last summer. I sprayed fungicide a couple or three times, but left the leaves on.

My outbreak is quite severe this year. I'm cutting all leaves all the way down to the rhysome and burning them. I'm also spraying with both a systemic fungicide with a spreader/sticker and a copper based fungicide. As soon as I get all of them cut, I'm going to do my best to drench the soil with fungicide.

I don't know how much this will help, but that's about all the information I've been able to find on the subject.

No only is it affecting the leaves, it has also gotten into the stems of some of mine, and has caused the lower flowers to be either very small or to not bloom at all.

Good luck to both of us,
Kay

PS. If anyone has a solution, please share it with us.

YOu are cutting ALL the leaves whether they are affected or not??? Will this not also kill the ryzome?????? I have had this for several years and thought it was the borer and soo mine has had a good head start on me......

I just trim leaves when I get brown spot. You can avoid over-head watering since the spread is by splashing. It's worse in wet years & almost non-existent in dry years. make sure your iris have plenty of air circulation. I plant mine in mixed beds, but on mounds 4-6 inches above the other plants. They dry out more quickly and I can mulch right up to the base of the mound without danger of rot. The mulch holds moisture for the other plants & keeps weeds down. I don't water unless I have new plants.

Unfortunately all of my leaves are affected. The coastal south is probably not the best place to grow these plants, but I couldn't help myself. Bugs and fungus are just a way of life due to our climate. Here we either have monsoons or drought.....there seems to be no in between.

I posted about this on GW, also, and got an answer similar to Wanda's...that the person had never lost an iris plant because of it.

My case is just so extreme is the reason I'm taking extreme measures. I have another order coming the end of July and I hate to put them in that same soil, but I have no other choice. Therefore, I'm going to go for broke on trying to rid it of any fungus it contains. I'm sure this is a no-win game, but I'm going to give it my best shot.

Great to hear about iris in Poplarville, Gaylams. I have a farm at Lumberton, MS and wondered if I could grow iris at my place. Sounds like they would need a lot of attention. I think I will stick to LA Iris there. Just planted my first this spring.

Listen to Wanda, she is the ruling Queen of the Irises.. :)

Yeah, I know. LOL Besides that, I like her advice. For my iris' sakes I just wish I had her climate! (However, for my tropicals' sakes, I'm glad I have mine!)

I just want all the flowers I see whether I can grow them or not....espcially iris, because my mother grew them. She would be so thrilled if she could just see how really beautiful they have become!

I'm glad you started this thread because I have Iris Blight this year and have never had it before. Every single leaf is infected. Some just have spots, some are completely brown. I have heard some local iris growers say they have never seen it this bad. It is just terrible.
I looked the problem up in some of my plant pathology resources and discovered that this blight can be either bacterial or fungal. They look similar. You can tell the differance by looking at fresh spots with a hand lens in the morning when things are still moist. The fungal blight will have a slight grayish color on the lesions which is the fungal mycelium. It will also have very tiny black dots which are the reproductive structures of the fungus. Turns out this is what I have. The pathogen is Didymella. Treatments include removing badly infected leaves and old dead leaves that are laying on the ground from last season. Good air circulation helps. Effective fungicides are Immunox, Mancozeb, Daconil. So I did a pretty severe trimming. I might even resort to trimming to the ground on some of my clumps because it it SO bad. Seems it has quit spreading and has slowed down since the weather has warmed and dried, I cleaned them up, and I started spraying them.

If you think you have the bacterial leaf blight there are not many options except sanitation (clean up everything), good air circulation, keep things dry, and immune enhancers such as Messenger, alfalfa tea, seaplant extracts, phosphites etc.

Good luck getting yours under control. The battle is on here at my house!

Robin

Robin, thank you for sharing your research. I'll have to look at mine under a magnifying glass. I'm betting it is fungal, also.

I never thought of using Messenger on iris, but if this wind ever stops blowing, I'll give it a try on some hot dry day.

I hope this thread will continue so that we can compare results of our efforts as time goes by. I would really hate to lose all these beautiful flowers.

Some of the ones I cut all the way down are putting up new leaves now. They are still quite short, but I see no signs of fungus on them. (Fingers crossed)

I'm going to try to drench the soil as much as possible with fungicide to avoid future problems if I can.

If you use a fungicide, use one that specifically says that it works on Leaf Spot and use a stickative - unless it's a systemic and then you don't have to. Lily Miller Disease Control has a fungicide with a good active ingredient and you need to alternate weeks with a different fungicide. Messenger won't get rid of any diseased material and may make leaves die back if they is sick. Don't worry about that though. I do use Messenger on my iris but I don't really know if it does that much good since I use a fungicide regimen.

Gaylams, which fungicide are you considering using? They are not all equally effective against this disease. Here is a good article by the University of Nebraska that gives registered fungicides for the disease as well as cultural control. http://nu-distance.unl.edu/homer/disease/hort/bulbs/IrLfSpt.html
I copied and pasted the portion about fungicides and cultural control because I thought it was very informative. I have been rotating mcobutanil and chlorothalonil with good success. Mycobutanil is the same active ingredient in Immunox for roses. Chlorothalonil is the active ingredient in Daconil.

Sanitation.
Remove infected foliage in the fall or very early spring.

Fungicide Application.
Several compounds are labeled for control of iris leaf spot. The list includes mancozeb (Fore), thiophanate-methyl (Cleary's 3336), mycobutanil (Systhane), chlorothalonil (Daconil, 2787), and Bordeaux Mixture (1997). The disease is listed as Didymellina leaf spot on many labels. A wetting agent must be added to assure proper coverage due to the waxy texture of the iris leaves.

Improve Air Circulation.
Overcrowded plantings should be thinned to allow better air flow.


Here is another good article by the University of Illinois. If you scroll down to the section on "control" it gives some very good cultural habits to help control the disease. http://web.aces.uiuc.edu/vista/pdf_pubs/628.pdf

Happy gardening
Robin

Forgot to say that if you really want to control it with a fungicide you should start early in the spring before you get signs of the disease. It's sure easier than taking off damaged foliage.

I have daconil and bordeaux mix already. I will use them for my next two sprayings. I previously used a systemic one time because I did not know if perhaps the rhysomes might also be infected.

I wonder if there is one that I could drench the soil with to try to kill the spores that are in the soil.

That was a great article, Thripmaster.

Thanks, and y'all keep the good information coming!

Kay

I wouldn't worry about drenching the soil. Didymella is pretty much a foliar disease with the spores residing on diseased leaves and old leaf/plant trash. Besides, no need to disrupt the natural flora of the soil when I think you can conquer this without doing that. Just clean everything up off the ground so the spores have no place left to hide. Get rid of all of the diseased leaves. Give it a good foliar spray every 7-14 days if you are using Daconil or Copper.

Like Wanda said, once you get things under control, keeping things more dry will also help considerably. Make sure they get plenty of sunlight and aren't staying wet in the shade. Make sure they are not over crowded and can't dry out. Don't ever work in your irises when they are wet so that you don't spread the spores. I have been looking at my clumps and realize they are probably too crowded. I am going to think them out after they finish blooming and see if that doesn't help. Who knows....maybe this is some kind of a strange once a decade occurance. I certaintly have never had this problem to this extent before and have never sprayed or done anything special to my irises. Must have been a strange spring.

I think that mine came on a shipment of purchased iris. At least that's the only thing I can figure out. Mine did the same - no problem and then a gradually spreading one until all of my iris are affected. Bummer!

did anyone dig up a rhizome and see if it was healthy?

My rhizomes are healthy.....

My rhysomes look fine. I finished the cleanup of mine today and sprayed good with Daconil. I dug up and burned some that I was not in love with to give them more room and try to get more air circulation.

I bagged all the cut leaves and stalks and they will go in the garbage on Monday. I think I had seven of those big leaf bags full.

I have some weeds in the bed and am going to try to clear those all out good, also, because they might be harboring those spores.

I really want to get these back in shape because I have another fair sized order coming the end of July and they will have to go into the same bed.

We had a hard freeze (18 degrees) for a week earlier this month. Literally melted some TB clumps. Some blades are recovering, others still look nasty. I am only trimming the definitely dead & hoping some bloom stalks are lurking in there yet....

Maybe the outside ones gave some protection to the ones near the middle. Hope.......

How cold can irises survive?

My iris go thru winters of -20 below zero easily when dormant. It's freezing them after they are green that is a pain. they won't die, but it will affect my blooms. I'll have to wait & see how bad it is later this month. :(

Wanda, 'hoping they will be just fine for you. It's kinda sad when we try so hard to do everything just right and are eagerly awaiting the surprises that spring brings and it brings freezing weather instead.

I had a handful of dwarfs bloom and the Intermediates are just about ready to pop. I'm seeing bud stalks on my early historic TBs too. Yes!

Hi all,
Can anyone recommend a specific spreader, sticker, or wetting agent? I have been battling iris leaf spot for 30 years, primarily through removal of infected leaves, but I would like to use a preventive spray technique instead. I sprayed a systemic (Immunox) and I know someone said you don't need a sticker, but it sure seemed like it needed one.
Thanks!!
Toxi

You can buy a spreader/sticker (labeled as such) from the seed store. If you can't find it, put a little hand dishwashing soap in your mix.

Bonide makes a spreader sticker that is very effective. If using dish soap, or oils, watch the amount carefully. And use a gentle dish soap, and not one with lotion.

Thanks Pollyk,
I have used soaps and oils in the past, often with disastrous results. I will look for the Bonide.

You're welcome. I hesitate to recommend oils, and soaps, as I have heard lately about a lot of people having problems with them. Apparently if applied improperly they suffocate the plants. Although I'm not crazy about using any "not natural" product, in this case I personally use something that's made specifically for the job. I'm sure a lot of people use oils and soaps properly and with good success.

I use the Bonide spreader sticker also....with good results.

I think I might have this leaf spot, fungus thing on my iris, too. I thought I had borers,
but did not find any in the rhizome. I did find some black bugs-what I call picnic bugs
in the axils where the leaves are actually rotting. It has been extremely dry in Indiana and
I have been watering daily. I could have splashed up fungus. The leaves have brown
spots, too. Is this what I have?

I only know about borers, but they usually don't go down into the rhizomes until after you have seen damage in the leaves. I have a lot of borer activity this year and don't want to use pesticides, so I am making a study of everything to do with the subject, and trying various approaches. My borers are still in the leaves, a few just beginning to reach the rhizomes.