In article , "John T. Jarrett"
wrote:

Last year I got the Schultz spray with the organic marigold insecticide in
it (trying to be organic) and someone on the list (animeaux) pointed out
that the OTHER ingredient was still toxic. :-/

So, I do a little research and go buy Sulphur Powder thinking that sounds
organic. I mixed a gallon with 4 Tbsp. as per the label and sprayed my rose
bushes. Boy, all those yellow drops on the new red leaves are some kind of
ugly. And the WARNING label on the sulphur is little better than that on a
fungicide! Wear a mask, don't go in the garden for 24 hours, don't get on
your skin - right, how do you NOT get it on your skin?!?!?! And just how do
you dust the bottom of a leaf, anyway?

Googleing for an hour now in this and other newsgroups (like
rec.gardens.roses) I've seen this the most often:

1-2 Tbs Baking Soda
1 Tbs Vegetable Oil
1 Tsp to 1 Tbs Liquid Soap

With kids and animals all over the yard, I am not going to apply a
fungicide, systemic or otherwise. But the sulphur says keep kids and animals
away, too.

What do you use?

Any help is greatly appreciated.

I suspect that where the fanciest most delicate roses are concerned, the
only way to not have black spot is to grow something else instead. The
usual organic remedy is a thorough almost weekly dousing with the formula
you outline (in various concentrations, but typically in a quart spray
bottle, one teaspoon baking soda, half a teaspoon of horticultural dormant
oil or light canola oil, & three or four drops dishwashing detergent to
help disperse the oil into the mixture -- really the soap isn't essential
& the Cornell Univrsity studies were of baking soda with horitucultural
oil only. The Cornell study showed that after four weekly dousings, both
black spot & powdery mildews were brought 95% under control (it often
eliminated black spot entirely, but never on the most susceptible
varieties). The mildew was gone with two applications, but blackspot took
recurring treatments to remain under control. The Cornell mix was a
half-percent solution of baking soda & half percent horticultural oil
(such as Sunspray), so not doesn't take much. Auburn University furthered
these tests & found that in addition to the solution sprayed on roses, it
was beneficial to start the season by spraying the ground area with
horticultural oil then placing a st erile mulch on top of the oiled
ground. This kept new spores from getting up into the roses, & also worked
really well on ground-grown veggies such melons & cucumber, & on herbs.

It needst be done regularly as only new leaves can be kept from the
affliction; already black-spotted leaves there is nothing you can do
about. Spraying has to be coordinated along with regular hand-plucking
infected leaves & discarding all leaf-fall instantly. Additionally, just
remove ALL leaves anywhere near ground-level to about 18" or so up the
branches, or splashing from waterings or normal rainfall with lift spoors
to the plant. Keeping growth airy rather than compact helps a bit. Unless
you shift to the most fungus-resistant plants, this will be an ongoing
chore, not something you can do for a while then finally be rid of the
blackspot. But I suspect this is just as true with non-organic fungicide
treatments, not the result of attempting to be organic.

Besides the spottiness left by wettable lime-sulfer, it doesn't work at
all in summer, & though moderately successful, baking soda & horticultural
oil worked better in the control studies. Neem oil also had high ratings.
I don't actually care for fancy roses but I inherited a big one & have
been able to keep the spot out of it by plucking alone. I finally cleared
out a place for a stepping-stone in front of this rose so I can stand back
there amidst the growth for as long as it takes to pluck bad leaves, I
keep the bottom clear of leaf matter. It's a hardy old thing though & this
might not be sufficient for fancier ones nor as quickly done with many
rather than one rose, & I would certainly go with the baking soda &
horticultural oil if it was getting unmanageable (or perhaps swap off now
& then first the baking soda mix, then just Neem oil, maybe now & then
lime-sulfer, so that no one thing builds up in the soil & perhaps
functions more in a "broad spectrum" manner to discourage funguses). One
negative thing about baking soda is with over use, it can alkalinize soil,
so an added annoyance could be having to lay down paper before spraying so
as not to drip too much baking soda into the soil (though the percentage
is very small & a single season's weekly applications wouldn't alkalinize
soil, & could be regarded part of the potassium percentage wanted).

-paghat the ratgirl

--
"Of what are you afraid, my child?" inquired the kindly teacher.
"Oh, sir! The flowers, they are wild," replied the timid creature.
-from Peter Newell's "Wild Flowers"
See the Garden of Paghat the Ratgirl: http://www.paghat.com/