horrible black spot - what would you do?

irismomof3May 14, 2012

Hi All -

I have been battling black spot on my iris for the past 4 years and I am at my wits end - I do not know WHAT to do.

First off - we have a LOT of bearded iris. We have a 2 acre yard and the entire thing is bordered by about a foot wide bed of iris. It is all in the full beating sun, at the top of a hill (in fact, it borders the yard and on the other side is all downhill rock so it should drain very well), and spaced well, so the fact that we have black spot at all is surprising.

I first noticed black spot about 4 years ago, and have kept up the basics - cutting away affected growth, keeping the beds clear, cleaning the shears between cuttings, etc etc. This spring we started in with fungicide spraying once a week because it has gotten SO out of control - to the point that the iris leaves begin to spot and wilt before it even blooms. At this point in the year, almost every leaf is affected. Nothing seems to be helping - and since the bed is so big it almost seems like I am doomed.

So my question is - What Would You Do? I am tempted to just weed-wack the whole bed down to 6" and then keep it clear from there to see if it helps? I am so upset - I think I am loosing my iris!

Sad note - this is the first year I would say the blooms have been affected. We probably had 50% of the blooms we usually do this spring. I am devastated. Any and all advice would be appreciated!

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hosenemesis(SoCal Sunset 19 USDA 8b)

I think we call it leaf spot here- if it's the same thing. I feel your pain.
I got it for the first time last year, and I am not happy. I pulled off all affected foliage on every plant last August. I cut down some of the plants to about eight inches high. This spring, I sprayed Daconil three times in early spring. I just found spots on three iris clumps today, so I'll cut off all of those affected leaves and hit them with the Daconil again. I won't have iris foliage that is not attractive, and I hate spraying fungicides, so if I can't lick this by next year I will have to rethink irises altogether.

    Bookmark   May 15, 2012 at 1:09AM
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ken_adrian Adrian MI cold Z5

I am tempted to just weed-wack the whole bed down to 6" and then keep it clear from there to see if it helps? I am so upset - I think I am loosing my iris!

==>>> liquifying.. a diseased plant.. and spreading the spores all over the entirity might not be the best idea.. dont you think .. easy.. but not best ..

when is the last time you thinned the heard.. and opened it all up for air flow??? improving the soil.. and just cleaned up the whole mess???

iris.. unlike a lot of perennials.. are not a plant and forget it forever type plant ... [some of the older ones are .. but not all]

if you decide to do something.. do it right.. not easy ...

one might suggest you take an small isolated area.. dig it all .. cut the leaves back.. replant about half of each of what you take out .. i dont know if bleaching or something might help ... and see if that area recovers enough.. to invest in doing the rest ...

with this years weird heatwave.. in march in MI [whats that all about .. 80 plus degrees] .. and repeated frosts and FREEZES ... the iris are not having a peak year .. and the leaves look horrible..

you might want to post a pic.. and let these sperts .. actually see what is going on ...


    Bookmark   May 15, 2012 at 8:19AM
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The problem with fungicides is that to work best you have to use them early in spring before the fungus appears, as they are more of a control than a solution. So early in spring fungicide as Renee says is good advice. Also keeping things separated more is good advice. I'm sure that with a large planting it seems overwhelming, but cutting the affected leaves off, thinning, and fungicide next spring are the best things. Our weather is weird, too, and the prevailing winds are different, so spores would be carried differently. Maybe that is part of the problem for you, why this came up recently. Good luck.

    Bookmark   May 15, 2012 at 8:31AM
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This is an article that gives a good explanation about leaf spot. In the article it says to test your soil pH, something I hadn't thought of. I get it once in a while but noticed that the German iris hardly ever get it. Hope this helps. Marg http://web.aces.uiuc.edu/vista/pdf_pubs/628.pdf

    Bookmark   May 15, 2012 at 8:48AM
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