Re: Re: CULT: diseased foliage
- To:
- Subject: Re: [iris-talk] Re: CULT: diseased foliage
- From: L*
- Date: Fri, 26 May 2000 08:44:26 -0700
>Now out here at school I have put in a modest iris planting where none have
>ever grown before. With about the same conditions as in my home garden,
>there is nary a spot anywhere and has not been. The plants placed there
>did come from home, but had most of their foliage cut off.
>
>I seem to recall that the spores of leaf spot are not windborne but fall to
>the ground or remain on dead leaves, then reach new hosts by being splashed
>up by rain. This does fit the pattern. It also seems likely that as with
>many water and soil-borne fungi, the spores are not long-lived, so no
>"spore bank" builds up in the soil.
>
>Bill Shear
I suspect that leaf spot can be windborne. I have no other explanation.
The largest bed of guest iris in my garden for the regional was virgin soil.
Iris from 22 hybridizers were planted there 2 years ago in July/Aug, and
most certainly I wouldn't expect all 22 to have sent perfectly clean
rhizomes. The entire first season there was absolutely no leaf spot. I
was so very amazed, I remember thinking how lucky I was and dreaming that
this bed would stay clean because somehow I had been successful in
preventing the leaf spot from coming in. The theory I had heard is that if
you don't get it into your soil, then you won't have a problem. I figured
this bed, being virgin soil, was clean enough to prevent what little might
have come in on the rhizomes from taking hold. When I was weeding the
following spring/summer after the planting, and into the late fall, I kept
looking very close for signs of leaf spot, and still there was none. It
was so unusual for me to see such clean iris, and they had grown and
multiplied quite well that first year. (my family remembers my bragging
about no leaf spot.) During summers and fall, I get a daily afternoon
moderate to light wind from west to east, because it is the downwind from
the large Laughlin Peak which is to my west. It blows accross my older
established beds and then across this new guest bed. During the
spring/summer/fall 12 months after the planting, it would have been hot and
dry, and I'm speculating that any possible leaf spot didn't have a chance to
take hold because the plants had lots of air space around them, and no
moisture. Of course, this was the time I had this blind belief that I had
beaten the odds of getting leaf spot in this bed.
Imagine the surprise and extreme disappointment when I found this bed
entirely encompassed with a mass amount of leaf spot during the second
winter, after the rains started. Every plant, no exceptions. Where had it
come from? I had been regularly weeding and removing aged leaves. It was
just like it came from nowhere!
My older beds adjacent to the guest bed which were upwind have had
leaf spot for years. My only explanation is that the wind carried the
spores into the new guest bed. So as you can imagine, I had to get into a
regular program last winter for spraying against leaf spot in the bed of
guest iris.
I have other beds behind my house that have been clean from leaf spot
for years. There is no other bed upwind from these backyard beds, and they
also have wind protection from fencing. So go figure. I'm sure everyone
has different stories.
I just wish there was a miracle spray that would kill all of it with
just one spraying! I realize I could move out all the iris and solorize the
bed... or maybe I should ask the neighbors if I could borrow their field!
Kitty Loberg, Calif.
p.s. Bill, your Wandering story was so very enjoyable... thank you for all
of your kind words.
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