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Re: Leaf Spot: Gene, Culture, Location, Gardener

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: Re: Leaf Spot: Gene, Culture, Location, Gardener
  • From: "J. Griffin Crump" <jgcrump@erols.com>
  • Date: Sun, 8 Feb 1998 17:27:48 -0700 (MST)

Jeff and Carolyn Walters wrote:
> Then in '95 (an unusually wet Spring, but not the first such in
> that time span) it suddenly showed up with about a dozen cultivars being
> seriously affected. I tried the approach of trimming and removing the
> affected leaves. In '96 the leaf spot spread further and I kept trimming.
> Last year I could see early on that the leaf spot was going to be
> overwhelming, so I started spraying. Daconil, sprayed once every three
> weeks, proved 100% effective in suppressing leaf spot through the bloom
> season.. . . However, last summer, perhaps due to the early development of
> the current El Nino, it was untypically rainy in August and early
> September. The leaf spot returned with a vengeance. Again Daconil was
> effective, but when I ran out of it, I followed the advice to rotate
> fungicides and tried Black Leaf Rose and Ornamental Fungicide (active
> ingredient: Dimethyl 4,4'-o-phenylenebis-(3-thioallophanate)). For whatever
> reason, this product proved totally ineffective here, although it is
> specifically labeled for iris leaf spot.
> Jeff Walters in northern Utah  (USDA Zone 4, Sunset Zone 2)
> cwalters@digitalpla.net
 Jeff -- Thanks for this detailed report. For what it's worth, my newly
planted reblooming bed, my new beds for newly purchased cultivars, and
my holding area for plants that need to be rescued from various perilous
situations (all of which are in my front yard) are relatively free of
leaf spot. My seedling beds in the back yard, however, are heavily hit
for about the third year running, despite the use of Daconil. And my
seedling beds which I lease from the county nearer Mount Vernon are
disastrous, again, despite regular use of Daconil. It does appear, at
this point, that the plague is transmitted by proximity. I should also
say that some varieties appear to be more susceptible than others, but
I, too, will have to keep better notes in order to identify the

Griff Crump, along the tidal Potomac near Mount Vernon, VA 

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