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Re: CULT: Leaf Rot

On Tue, 29 Apr 2003 19:06:14 -0700 "Fleurdelis/Acorn Hill Publishing"
<fleurdelis@snowcrest.net> writes:
> Hello All:
> I've posted a pictue of this stuff on Iris Photos (I hope) and would 
 At first the leaves look sort of wet 
>Somethimes the leaves just sort of dry up.  Last year Iris 
> Talkers thought it might have been frost, which could still be likely
as we 
> have had a
> very cold April but I tend to think it is something more than that.
I'm going way out on a limb here but it sounds like you could have two
different things happening and both could be induced or aggravated by the
stress of cold wet weather (and other stresses). When I notice the
wettish semi transparent areas usually starting as a 1/4 to 1/2 inch
circular area on the lower area of the new growth area on a leaf it
usually follows a cold night. The damage then quickly grows outward and
across the base of the fan and it topples over. The top of the fan can
look fine at first glance and looks like it has been knocked or broken
off. We have problems here with botrytis and flux type diseases which can
create an imbalance of pressure within the cell wall (as can the frost or
stress), they collapse and other disease and damage enter and take over.
Our rot at my place is usually always active during cold spring weather,
it does not stink like the warm humid crown rot stuff other areas may
experience, and if the weather warms up and dries up quickly, your plant
or some of the increases may grow on through the attack. BUT...and I am
shouting...in my experience, it will return everytime these rot
conditions are favorable on what is left of that plant. So, use a
systemic fungicide and throw away dead diseased tissue where it cannot
contaminate anything. My second and third year clumps are more
susceptible, I'm guessing because of the density of the clump, and the
fact that the disease has been working on it for 2-3 years, probably
semi-dormant or unnoticed just waiting for that cold wet spring weather.
In my type of rot, you will also find small grey/black granuals in the
soil near the infestation and  many times another blacker and more
crystalline structure growth on the bottom of the rhizome. The roots
broken off from the diseased rhizome look white and strong in the
ground...except they are no longer attached to the mother plant and I am
sure are dying slowly and will carry the disease. Next to the decaying
rhizome, the roots are hollow and brown.  Neil Mogensen aptly called the
greyer crumbles, grapenut like things. If you have a plant that is
rotting away, treat it right away. It may live in spite of the early rot
but if left untreated systemically, my experience is that it will remain
a host for that rot and it may come back even stronger and problably in
many more plants the next year. Does this make any sense? I think my soil
and garden just must be a good place for this rot to culture. I have been
testing and treating religiously for several years now but it has been a
struggle. We started 20 plus years ago with really dead, flat concrete
type soil. Good luck. They are worth it....and some are easier and do
better than others so keep trying!
Char Randall
Melba, ID Zone 6
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