Re: CULT: Fungal Leaf Spot

Hi Colleen

I read Paul Archer's posts and think he also misspelled the systemic.

I think he means Benomyl (which I use) [Methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate]

DuPont produces it under the trade name Benlate.

In oder to understand your treatment you need to understand how the leaf spot spreads. Once the first spot shows on the plant it has and continues to release spores. The spores are generally spread by wind and fall to the ground. They are most often spread to the plants by rain splashes.

In my location in California, we get fall and spring rain, but no summer rain and very little morning dew.

So, I spray with Benlate once in the fall and in early spring (occasionally a third time depending on the rain). I think Paul was right that as the iris grows, the new leaves get less of the Benlate because it get absorbed by the plant and washed out of the root zone by rain. After the rainy season, I don't really need to spray again. I use drip irrigation so I don't create my own "splashes".

I also spray with a product called Pro-TeKt by Dyna-Grow. I was tripped to this product by Jay Hudson of The Iris Gallery (grows mostly beardless - PCIs, SIBs, SPUs, JIs etc). Pro-TeKt contains a silicate that provides an extra layer of physical protection. I spray Pro-TeKt after I spray Benlate.

I use both products on everything I grow - SPUs, TBs, SIBs and all the other 13 or so iris species we have plus almost everything else in the yard. I had very little leaf spot this year and had I had more time to spend in the garden would probably eliminated it.

You will have to adjust the application strategy to your environment, but should start with cutting off every speck of leaf spot you find and putting it in the trash (do not compost it) - but you probably know that already.

I don't know if either of these products are available to you. If not most any fungicide would be good, but aI particularily like systemics because they seem to work better and you don't have to use them as often.

As to spreader stickers, almost any of them will do, even liguid soap added to the spray works fine.

Let us know how things work out.

John

On Sep 8, 2005, at 12:23 PM, Colleen Modra wrote:

We've got the worst hail damage I've ever seen on our irises this year. Some
plants look like they've been shredded by cockatoos. But all plants,
especially the bearded irises are completely covered in white hail damage
spots.

In my experience the hail breaks the waxy coating on the iris leaves and makes
them far more prone to fungal leaf spot. We normally get a bit but have never
sprayed for it.
However this year it is the Aust Iris Convention here and we'd like our
gardens looking extra good, not hugely worse than ever.

For those of you who do spray for funal leaf spot, what fungicide do you use
and what additives do you add the help it stick?

Many Thanks

Colleen Modra
Adelaide Hills AUST
zone 8/9

colleen@impressiveirises.com.au

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John                | "There be dragons here"
                         |  Annotation used by ancient cartographers
                         |  to indicate the edge of the known world.

List owner iris@hort.net and iris-photos@yahoogroups.com
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USDA zone 8/9 (coastal, bay)
Fremont, California, USA
Director, American Iris Society
Chairman, AIS Committee for Electronic Member Services

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