Re: brown leaves
- Subject: Re: [sibrob] brown leaves
- From: Ken Walkup k*@cornell.edu
- Date: Mon, 07 Jul 2003 07:56:03 -0400
Margaret,
If I were you, I'd take a piece of the infected plant NOW to the
nearest plant pathology lab; check with cooperative extension if you don't
know where to go. Your plant could have one of several fungus infections
which are destroying the root system, hence the brown leaves. Which
fungicide to use depends on which fungus your plant actually has. Could be
Botrytis, Pythium, Phytophthora, etc.
Alternatively you could dig & destroy the infected plant. If you
only have one or a few infected plants, you could try digging them, washing
off all the soil, and soaking the whole plant in a 10% Clorox bath for ten
or fifteen minutes, then rinsing thoroughly. Pot the washed plant in
soilless mix & don't re-plant in the ground until you are sure the thing is
disease free.
Over the last several years I've had a lot of trouble with fungus,
affecting all types if iris I have. Setosa and Sino-Siberians seem
particularly susceptible. While these funguses are normally present in the
soil, I think my problems started with some compost I brought in from a
very large pile at Cornell University. This was very well mixed and had
gotten so hot that some of it had an ashy look, but still, the fungus got
through. I've taken samples to the path lab twice, and they have diagnosed
every type of nasty fungus there is, except Botrytis. I've only had
partial success in defeating the stuff, and at the cost of a lot of extra
work and expense. It truly takes a lot of the fun out of growing irises.
I have not been able to see that the browning occurs on the center
fans first. Perhaps that is because I don't seem to have a Botrytis
problem. The usual course of the disease is: the plant looks healthy
until late May, or a couple of weeks before bloom. Then a few fans start
turning brown. Left unchecked, the progress of the fungus infection can be
very rapid, with susceptible plants killed completely in two or three
weeks. There is an interesting contradiction here; you'd think that
fungus would be worst when the weather is wet, as it often is here until
early June. It's when the plants begin to be stressed by dry weather that
they are most likely to be killed by the fungus.
I truly hope you can nip this thing in the bud, before it becomes
a general problem for you.
ken Walkup
At 07:28 AM 7/7/2003 -0400, you wrote:
>Ok, I know the yellowing/browing middle leaf routine on bearded fans; I
>have never seen it on siberians. Yesterday I checked out Sprinkles to
>remove the spent stalks and noticed that it looked ratty. Closer
>inspection shows a mix of green and brown leaves and the brown leaves
>are mostly the middle fan, and they can be pulled out. What dreadful
>condition do I have?!
>
>Incidentally, this plant has never been ecstatic but it has survived and
>bloomed and the blooms are lovely.
>Margaret Boehm
>Wilton, CT zone 6
>
>
>
>To post to Sibrob: sibrob@yahoogroups.com
>
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