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Irises: A problem with my bearded iris.

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gemini_sage
Winchester, KY
(Zone 6a)

May 28, 2005
3:22 AM

Post #1502873

I'm seeing symtoms of something in a few of my bearded iris that I've never seen before. 3 or 4 of my varieties have yellowing leaves with brown spotting. They are also blooming beautifully. This is my third year living and gardening here in this woodland environment and the first year I've had a striking bearded iris display. When the symptoms showed up on the first, it was one that has a lot of vinca minor as a ground cover around it and I thought the rhizomes may need more sun on them. A few days later I noticed it on a couple more that have good air circulation and no ground cover around them. Any ideas what the problem is and what to do about it? I'll try to post some pics.
Janiejoy
Silver Lake, OH
(Zone 5b)

May 28, 2005
5:50 AM

Post #1503036

You most likely have iris borers.

You'll have to dig them up, cut off the leaves to make a fan of about 5 inches high, soak them in bleach water, let them dry, cut away the mooshy parts of the corms, and replant.

You will find the tiny holes where the itty bitty caterpillars get in, and they bore down the leaf and into the corm and scarf themselves full of yummy iris. Then the iris rhizome rots. They are really stinky and slimy and when you dig them up you may likely find big pink ugly caterpillars munching away.

Lost about 12 beautiful expensive irises I got in a wonderful co-op here on DG. After that, I was ruthless, pulled those puppies up, washed them off, and cut out the bad parts. Then put them back into the ground and a few of them lived.

There is something you can get to fight them - nematodes are a natural way, they introduce a bacteria that kills the caterpillars.

Here's a link with more information than I knew: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e122irisborer.html

Let us know how you fare. If you get them early you can often squish them while they are IN the leaves (cutting the leaf underneath the hole or where the burrowing stops will stop the caterpillar).

Just make sure in July you clean up after your irises so it doesn't happen again!
laurief
Deer River, MN
(Zone 3b)

May 28, 2005
12:32 PM

Post #1503295

I need to see close-up pics to understand what you're describing (esp. the "yellow" part), but spotted leaves are not an indication of borers. Spotted leaves indicate either a fungal or bacterial leaf disease.

Laurie
gemini_sage
Winchester, KY
(Zone 6a)

May 28, 2005
1:20 PM

Post #1503373

When I lived just 30 miles east of here my beardeds grew like weeds with almost no attention-never saw the first sign of a pest. But that was in the bluegrass part of the state, now I'm in the foothills of the Appalachians in a mostly wooded environment. 1/2-2/3 day of sun is the most I can give them, so I've been unsure how they would fare here. When so many of them bloomed for me this year(11of my varieties) I was all pumped up and ready to re-start my quest for more varieties, but now I'm not sure. If the problem is iris borers, I'm wondering if spraying the surrounding area with neem would help, and if it's fungal the neem still may help. I've taken some shots of them with a camera I borrowed from a friend; once she gets them on a disc I'll post. Thanks for the input, Neal.
cultivateweeds
Salem, MA

May 28, 2005
2:24 PM

Post #1503457

Hi Neal, reading out of "The Ortho Home Gardener's Problem Solver," they suggest two funguses, either rust or "Didymellina leaf spot." With rust, the pustules are powdery; with the other the spots are brown and surrounded by wet, yellow areas. Both seem to attack only the leaves, not usually the flower stalks, and both can kill the plant indirectly over time by weakening it. Both spread during wet weather and wind, and overwinter on iris debris. Rust apparently attacks other plants, but the D fungus is limited to iris and "closely related plants." With D fungus, "After the plant has flowered, the spots enlarge rapidly and may join together to form blotches", while the rust seems to stay spotty. Ortho, of course, recommends spraying with a chemical, chlorothalonil. Looking in my organic gardening books, most recommend controlling fungal diseases in general by spraying the leaves weekly with diluted compost tea. If plants are already infected, they recommend adding a 1 tablespoon each sulfured molasses and household vinegar to the spray. They also recommend spraying leaves in late winter/early spring before fungus appears, with 1 tsp. salad oil and 1 tsp. biodegradable dish soap in 1 gallon water, "usually daily the first week, then weekly, and if it holds out, then monthly" which sounds like a lot of work. Haven't tried any of these myself! but do soak my hand tools in mild bleach water (5%) when working with diseased plants. Hope some of this is helpful.
doss
Stanford, CA
(Zone 9b)

May 28, 2005
5:38 PM

Post #1503808

It certainly sounds like leaf spot to me. If it's leaf spot, the first thing you have to do is to cut off as much of the affected material as possible. This year I did have to use a fungicide specifically mentioning Iris leaf spot. If you do this, you need to use a stickitive added to the fungicide. The best method is to alternate two different chemicals and spray every two weeks. Continue to cut off diseased foliage. If you are seeing some spots in the leaves that are sort of transparent those are the beginning of the brown holes and a good indication of leaf spot.

Put debris immediately in plastic bags in the trash or burn it. Don't put it into the compost or leave it on the ground.

I just had this for the first time this year. Apparently, it's a biennial fungus so you have to keep after it in the future.

Be careful of walking through the Iris if the foliage is wet. You can easily transfer the fungus from plant to plant that way. Nasty stuff.

It really doesn't sound like rust.

If you are interested in using chemicals, email me and I can send you a list of recommendations from a grower. I'm sorry to hear that you have this. Iris are tough though. Apparently they can generally survive this if they are not too affected even if you don't treat them although the grower who I called was pretty insistent that I should treat them right away.
pirl
(Arlene) Southold, NY
(Zone 7a)

May 29, 2005
1:02 AM

Post #1504665

I'm just a lurker who likes irises. After reading these posts all I can say is
"Who thinks gardening is just puttering around?"
doss
Stanford, CA
(Zone 9b)

May 29, 2005
1:12 AM

Post #1504685

pirl, have you ever played golf? 'puttering' is only fun if you figure out how to keep your plants from croaking. :-)
gemini_sage
Winchester, KY
(Zone 6a)

May 29, 2005
4:18 AM

Post #1505139

It's sounding like leaf spot to me. Thank you both for the great info. So far I have'nt had to use any chemicals in this garden, so I'll try the organic method. I'm wanting to tear into them right now, but the blooms are so nice now. As soon as the last one fades its surgery time!
doss
Stanford, CA
(Zone 9b)

May 29, 2005
5:02 AM

Post #1505202

You should take as much damaged foliage off as you can now. You don't have to remove the stems and flowers. But I wouldn't leave the foliage on any longer than you have to. You do have to leave enough of the foliage on for the plant to survive of course.

Good luck!
pirl
(Arlene) Southold, NY
(Zone 7a)

May 29, 2005
11:10 AM

Post #1505360

Hi doss - my Florida friend calls gardening "puttering around". I thought golf had "putting greens"?
Anyhow, I work darn hard and do no puttering and actually resent the put down. The local garden club does not select "putterers" for their garden tours. Thanks for letting me vent!
inanda
Winnipeg, MB
(Zone 2b)

May 29, 2005
11:49 AM

Post #1505408

We def. need the pics. In the meantime, give us a better description of the yellowing and spots. Did they start as watery or greasy looking round or oval spots. After a day or two getting larger, turning yellowish to brown, often developing a distinctive red/brown order to the spots?

OR

Large irregular spots, mostly towards the upper margin of the leaf, appearing first as water soaked areas that quickly turn brown? These spots lengthen downwards following veins.

Have you been having wet warm weather?

Don't forget when cutting off damaged material to carry a container of disinfectant (I use full strength Chlorox) to make sure the implement is disinfected between each cut. Otherwise you may be spreading the problem from plant to plant.

Paraphrased from World of Iris (WOI), the irisarian bible.

Inanda

doss
Stanford, CA
(Zone 9b)

May 29, 2005
3:29 PM

Post #1505731

Oh, and also, make sure that you arent' having slug damage. This can sometimes look like streaks in the foliage.
gemini_sage
Winchester, KY
(Zone 6a)

May 30, 2005
7:38 PM

Post #1508422

I just cut some leaves and brought them in to examine closely. I seems to start with irregular small spots scattered here and there on the leaves and the spots are visible on both sides of the leaf. The spots themselves are light brown and dry. After a leaf has several spots yellowing starts in streaks through the leaf and and then turns from yellow to a dry brown. In a dry brown leaf I checked, the spots are still visible, and when feeling the leaf between 2 fingers, I can tell that the spots are thicker than the rest of the leaf. I've cut into the spots, but can't find any insect or larvae. There could be eggs there that are too small to see.
This has been a cool, dry spring for us here. There is nothing slimy, sticky, or wet on the leaves. The soil is well drained, but moisture retentive. I have'nt noticed any indications of water stress from anything in the garden, and have been planting so much that most of the garden is getting watered pretty regularly. This is sounding more puzzling. Thanks for the good tips.
doss
Stanford, CA
(Zone 9b)

May 30, 2005
8:43 PM

Post #1508570

If you want to go organic, you must have an organic garden store somewhere near. Maybe they can give you a better diagnosis. Or you can borrow a digital camera. Insects and larvae won't be in the spots. If you have borers they'd be between the leaves near the Rhizome.
Here's a website with a photo of Iris Leaf Spot (on the second page).

http://www.oznet.ksu.edu/news/sty/2003/iris_disease043003.htm
gemini_sage
Winchester, KY
(Zone 6a)

May 31, 2005
11:19 AM

Post #1510001

Those pics look like mine. Thank goodness it is'nt fatal. I've been working hard toward opening the garden up for air circulation. Last year I let some things that were just too happy get out of control and they started encroaching on some less vigorous babies. I suspect this got started last year when it was a wet growing season and other plants growing around the iris hid the symptoms. Thanks so much for your help.
doss
Stanford, CA
(Zone 9b)

May 31, 2005
3:42 PM

Post #1510465

Good luck! You just take care of those lovely Iris. We'll all be thinking of you. If it makes you feel any better, my Iris were just divided last fall and all have breathing room but it was a wet fall here. I just have to keep after it for awhile now.
roisemaire
Vincentown, NJ
(Zone 6b)

June 3, 2008
6:22 PM

Post #5047043

Gemini...I can see you've gotten tons of good advice, almost all of it pointing to Leaf Spot Fungus; and I agree, the response has been "spot on." That wasn't meant to be funny...this is a real problem for Iris lovers.

I've been struggling with this same fungus for a few years now, and one thing I've noticed: the newer (always expensive) hybrids seem to be most susceptible to Leaf Spot Fungus. I was checking all my beds yesterday, and it dawned on me that the old purple Iris my parents gave me in the 70s are 99% free of this problem. They didn't have a name for them, so I call them "The Old Purples." Perhaps hybridizers need to breed back to the stronger old standards to fortify the immune systems of the new hybrids. Just a thought.

One more bit of advice from an old Iris lover...use soaker irrigation, when needed. Soaker hoses minimize splashing water on the leaves, and it's more economical than using sprinklers where water is immediately evaporating in the air. Iris don't need a lot of water, once they're established. I only give mine an occasional drink during the searing heat of our South Jersey summers.

The best advice of all...keep your Iris plants free of withered leaves on a weekly basis; don't allow them to accumulate around the rhizomes and you'll be ahead of the game at clean up time in the fall. Another benefit is...you'll be denying slugs and other creepy crawlers a place to hide among the plants, and it doesn't cost you anything.

Rose.
gemini_sage
Winchester, KY
(Zone 6a)

June 5, 2008
1:15 AM

Post #5054947

I ended up going the drastic route, I moved to another town and left all my iris behind, LOL! However my friend who moved to my old place has made some headway fighting the scourge. I've started over with them and this location is perfectly suited for them, lots of sun and we're on hill and get continuous breeze.

Good thinking on back crossing with the tried and true old tolerant varieties!
KristaJoy
New Richmond, WI
(Zone 3b)

June 5, 2008
6:55 PM

Post #5058481

I have a different problem. I love Iris and I am new to growing them. Two years ago I planted some. I have several different varieties. Our soil is heavy clay. Half is mulched and the other half is just dirt. The plants look good considering we had three late frosts and a hail storm. The problem is the buds get soft and don't open or they open slightly and wither.

irisMA

irisMA
South Hamilton, MA

June 6, 2008
3:15 AM

Post #5060917

It could be frost damage which would hurt the buds while they were forming but not damage the whole plant.

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