Sick iris, help!!

Last year my irises were beautiful! This year they have something wrong with them. A number of them had buds that rotted; thought maybe they had been frosted. Others did not grow much, I just dug one of the small ones up to check out what was going on under ground and the rizones look fine, not soft, didn't see any holes. This is what the leaves look like. My other two beds (which of couse aren't my best iris), are fine. I am in sand so water isn't usually a problem. Anyone know what the problem is and what I should do?

Another view

I would do two things
pull a sick leaf off and see if there are borers in the leaves. If not check that rhizomes. if not look for grasshoppers or other insects that can damage.
:)
A

Cut all the leaves off about 2 inches above the ground. Apply a generous helping of Bayer
Merit, either liquid or granular. There is time for new leaves to grow and the irises will only
be set back a bit. You won't know the difference next year. You may have some leaf spot
plus some chewing critters which will spread the disease, if any. I have cut mine back many
times for severe leaf spot and they always seem to recover.

Merit will not help the spotting but will kill the leaf eaters, or it is supposed to. Latest treatment
for borers now that acephate and some of the other organophosphates (??) are being phased
out due to extreme toxicity. Absorbed thru the roots up into the leaves as a systemic
treatment. Normally applied in the spring but you may need help now.

avmoran, I tore a leaf apart and found no critters; I dug one up and it looked healthy; there is some chewing going on but not enough, in my uneducated opinion, to hurt them.

oldgardenrose, I will cut the leaves down to two inches like you say. Will my local nursery carrry Bayer Merit; I have never heard of it but there again, that doesn't mean much.

Oldgardenrose, you are good at explanations, can you explain about leaf spot? I think I have had some forever and know absolutely nothing about it. Maybe someone else would find it interesting also. Thanks

There are about as many opinions of how to care for irises as stars in the sky. I prefer the
cure or kill approach. Trimming the leaves close to the ground will help clear up the fungal
leaf spotting but there are no guarantees. I use a plastic coffee container with a strong
bleach/water mix to dip my scissors between each plant. There are even cautions about
walking among or touching multiple plants when they have diseases.

I had a 4x4 block with five Batiks spaced probably 2 feet apart. Late spring I pulled all
the weeds and grass, picked out all dead leaves and had them well cleaned. By the end
of bloom time they were a mess with most of the leaves completely covered with spots
and many of them lying on the ground. A block next to them had great green foliage and
only had a few spots but they were different irises. Gives me pause to think some plants
are inherently susceptible, by prior infections, to repeat infections regardless of efforts
to treat them. We have had two seasons in a row of excessive rain and cool temps
during the spring growing period so all my conclusions may be completely incorrect.

Sunlight and ventilation are the best defense against fungal leaf spots. Bacterial leaf
spots may be controlled with a mild bleach/soap spray but I have not had enough of
that problem to advise a cure.

After I decided all my modern TB's had to be scrapped, I cut the leaves down flush
to the rhizomes. I chopped the new leaves and weeds today and most of the irises
had sprouted new leaves about 8 inches tall after about 4 weeks. Much the same
as if you had dug/trimmed/replanted for next year. That is why I have said when in
doubt about diseased leaves, cut them off. They will recover although, obviously,
not the same as if they had been healthy untrimmed plants. I cut all of mine last
year and had the best foliage and blooms this year since they were originally planted.
Still had a spotting issue due to all the rain.

Bayer products should be available at almost any garden center. I know WM and
Lowe's carry the Bayer line. I think Merit is a brand name. Look for the active
ingredient 'imadacloprid'. I bought some last fall but did not use it this spring because
I had a few ounces of 'acephate' left over. I think it was irisMA who clued me into
Bayer after some postings last year about toxic chemicals.

Google imidacloprid or Bayer Merit to get the complete details. You can check it out
much more accurately than I could relay the info.

Hope this helps but there are members on this forum who have forgotten more than I
will ever know about irises. Multiple opinions and ideas are always best.

http://web.aces.uiuc.edu/vista/pdf_pubs/628.pdf

This is the best explanation of leaf spots I could find. You will need Adobe Reader for pdf files. If
you do not have it, download it for free. There are a lot of info sites requiring it. Otherwise, just
google 'iris leaf spot' and several university sites come up.

This message was edited Jun 24, 2009 8:49 PM

Afraid it was not I, who knew about the Bayer, obviously lots of people do. After 4 solid days of rain & drizzle we will see what leaves are like. I worry about the possiblity of bortrytis on the peonies.

thank you, the site you recommended was very interesting. Sounds like maybe all is not lost if I work at it. I am going to cut down my leaves immediately; I have had some brown leaves for two or three years but the iris didn't seem to care. I guess it finally caught up with them! My fault; I know. I will also apply the Bayer Merit and have faith that all will be well.

It is so nice that all the fine people on Dave's Garden help each other out. Where else can I find anyone else that cares? (Yes, I know, my DH does but we are both without a clue. lol)

I tried Daconil for the fungus but had no luck. Could have been my failure to begin early
enough. Once the lesions begin, it is too late. I learned something myself. I knew that
the systemic insecticide for borers, Acephate, had to be sprayed on the leaves by the
time they were six inches or so and repeated at least once later. It was absorbed into
the leaves and killed them when they made their first bites. I could always see nicks in
the leaves but rarely ever had any borers. Imidacloprid is absorbed into the roots and
travels up thru the rhizome to the leaves. I have some Merit for shrubs and small trees
where it is applied according to the height so it can migrate into the leaves.

If you ever find a good systemic fungicide that is available thru garden centers, let me
know. My peonies have some black spotting from all the rain we had all spring until
just recently. It was 100 in the shade about 30 minutes ago so I don't think it will be
a major problem.

One of my last clumps before digging. This plot has a high sand content over a sloping
clay base so drainage is almost perfect. Direct morning and afternoon sun--midday is
shaded until summer. This is not the worst example. Donating all of them to the city
yard waste program.

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