One of the problems with the "this works for me" school of rose tips is that the information is often incomplete.

Let me give you an example: in my garden in east Tennessee at 1000' elevation, my big white fluffy cat sleeps in my tea rose bed in the spring. By July, the roses there no longer have Black Spot. So, you all should all get a big white fluffy cat to sleep in your rose beds in spring. (Not that everyone doesn't need a big white fluffy cat)

The problem is that the cat has nothing to do with the spread of Black Spot. What stops the Black Spot in my rose bed is the heat and dropped humidity of my summer growing conditions. It happens annually.

Ashes + water equals Lye. Too much will damage organics. (Including our skin, etc.)

Rust is a fungus: it doesn't disappear, although it may appear to the naked eye- you've just knocked the sporangia off. It will come back the next year if it the deuterospores formed. Logically, without the addition of moisture do you think that ashes on the top of the soil will affect the pH of the moisture six inches down...and that difference in pH will translocate upwards in a day and that the fungal hyphae will pick it up, shrivel and die in the same 24 hours.

PM- well, the Empress Josephine did have her serfs wipe her roses' leaves with baking soda solutions. That at least is changing the local pH raqpidly, very locally.

I don't think it's just the baking soda that worked on mildew. Pretty much anything which forms an insulating layer over the leaf surface will prevent mildew spores from germinating. Oils, fungicides, antitranspirants, milk, etc. all provide a film which prevents the spores from coming in contact with the leaf surface, hence preventing them from germinating.

In their climate, The Huntington Library found years ago that over head watering early in the morning appeared to prevent mildew spores from germinating during periods when it was a particular nuisance. There have been many articles offered considering using cooking oils instead of paraffinic oils, and each of those has seemed to provide protection, too. If a film of water can provide the same effect, it has to simply be anything appropriate to use which covers the surface and prevents spore to tissue contact will prevent germination. Of course, more lasting effects are provided by oils, fungicides and bacterials which interrupt the germination process, but initial infection has been shown to be prevented using plain water.

I'll have to figure out where to find wood ash. I'm in a fire zone, hillside and burning wood in the fireplace isn't encouraged due to these factors, current wind issues and air quality concerns. I wonder if ashes from the BBQ might work? They're from commercial charcoal and Mesquite chunks. Kim

Hi anntn: I agree with you 100% on wood ash. I was presenting my case against wood ash (damage to roots) on the Soil Forum. However, wood ash is high in potassium, well-known for suppressing diseases.

Hi Roseseek - I'm glad to hear from you, thank you. I learn so much from you, and appreciate your info. very much. I was about to do a pH test on wood ash using red cabbage juice as indicator, but could not find any ash (we converted our wood fireplace to gas-burning fireplace!). I have a gas grill too. Here's info on organics from http://www.thctalk.com/cannabis-forum/showthread.php?5-Worm-Farming:

High N:
Blood Meal (NPK 13-1-0)
Coffee grounds (NPK 2 0.3 0.3))
Felt (NPK 14-0-0)
Hair (NPK 14-0-0)
Tea grounds (NPK 4,15-0,62-0,4)
Worm Meal (dried & ground worms) NPK 10-1-1
Greens, leaves & meals, alfalfa, stinging nettle
High P:
Bone Meal generic NPK 4-21-0
* steamed NPK 13-15-13
* burned NPK 0-34,7-0
Shrimp Waste NPK 2,87-9,95-0
Tea Leaves ash NPK 0-1,66-0,4
Wheat bran NPK 2,65-2,9-1,6
Oats, Chicken Manure
High K:
Banana skin NPK 0-3,08-11,74
Molasses NPK 0,7-0-5,32
Potato skin NPK 0-5,15-27,5
Wood Ash NPK 0 1 5
Wood ash (broadleaf) K 10%
Wood ash (coniferous) K 6%
Alfalfa, ashes, potato wastes, peel & skin (-ashes, too)
High Calcium:
Poultry manure (0,5-0,7% dry), dolomite lime, egg shells, bone meal
Note that its usually thought that worm castings is high in calcium (perhaps with the presumption that lime or eggshells are added during the process).
High Iron:
Stinging nettle (Also high N)
High Magnesium:
Dolomite lime, poultry manure, epsom salts

Here is a link that might be useful: Missouri State data on nutrients

Copied from above: Here's info on organics from http://www.thctalk.com/cannabis-forum/showthread

It's all starting to make sense now.

Be careful about adding wood ash to an alkaline soil. It is used as an amendment to neutralize acid soils. It does add nutrients.

Here is a link that might be useful: Agricultural use of wood ash, Clemson University report

Thanks, yes, I know how caustic it can be and we DO have a relatively high level of alkalinity. I've usually thrown the ashes (after wetting them thoroughly and allowing them to air dry to make sure they're cold) out on the lower hill where they will hopefully help kill weeds and eventually be recycled. It seems the best method of eliminating disease in the garden is still a shovel, followed by good selection. Kim

I've found home brews to be iffy at best and can be lethal at their worst. Tried one once that had cooking oil in it. Yep, cooked the leaves right good!

I learned a long time ago, in these parts with the intensity of our sun, heat and evaporation, anything oil-like is going to cook the foliage. It doesn't matter what time of day or rinsing it off or not (as if you CAN rinse off an oil). I've successfully used Ultra Fine and Jojoba oils in Pacific Palisades long before the fall heat (six to eight weeks prior) without much damage, as long as the plants weren't allowed to dry out too severely. But inland here, our sun, heat and aridity are just too extreme for oils to be safely used. If the product can be phytotoxic, our conditions will encourage it. Filter the sun enough through fog and other humidity, reduce the temperature extremes sufficiently and they can be quite effective, but definitely not here.

It's proven that baking soda suppresses powdery mildew, as do other organic remedies such as sulfur, potassium bicarbonate, milk and oils, and even plain water can help if conditions are not too bad.

Rose rust is only rarely a problem in upstate NY, or anywhere else in the US beyond the West Coast. I have only seen it once during 35 years of looking at roses in North Carolina, and that case vanished as soon as the weather warmed up. So it's no wonder that wood ashes "cured" rust in NY, if ever it was there in the first place. I seriously doubt that ashes on the soil would affect any fungus disease. I doubt if the wise old gardener being quoted actually knew what rose rust is. Some people use the word "rust" very loosely.

Wood ash contains such powerful alkalais that it should not be applied to any rose soils except those that are seriously and chronically too acid, according to a soil test. Generally these would be sandy or peaty soils.

Michael,
I'm not sure if the Rose Gardens in Hershey PA have cured their rust problem or not, but for at least two fall seasons, Rust ruled their rose gardens. From a distance the roses appeared to be blooming well, but up close, the roses were totally defoliated from the ground up to eighteen inches (one year) and to twentyfour inches (two years later) and the surviving leaves had millions of orange spots (as seen from above). Turn over any leaf, and the undersides were bedecked with individual 'bumps' of orange, the size of the letter "o" in most newspapers. In addition, the reproductive spores, the ones that carry the disease through winter and are stand out black- that look larger than the individual orange spores (and with a hand lens look like two wizard hats glued together at their brims)were all over the undersides of the roses. No roses there appeared to be immune.

Elsewhere in the east, the rugosas at the Royal Botanical Garden in Burlington Ontario had rust in early to mid June.

These have led me to worry that somebodys going to produce sick roses and sell them in the east and because the plants were asymptomatic when sold= they'll be as much a problem as daylily rust almost was.

Thanks, Ann. That is certainly very surprising information about Hershey PA, since they have warmer summers than we do here. Back when I used to read the annual reports from the NC path lab, there were a few diagnoses per decade of rust, only at the highest elevations such as Highlands and Boone. The case I saw personally was in Spruce Pine, which is slightly cooler than Asheville, during a very cool foggy first flush. About a third of the varieties seemed to be resistant, which I think is the typical experience on the West Coast. The grower had about a hundred modern roses, and many of them looked terrible.

I've ordered so many roses from CA and OR, I'm sure some of them came with some rust spores on them, but I've never seen rust here in Asheville.

I like the fluffy white cat cure, must get one, lol!!

Don't try a yellow cat! I used one once, and my roses got terrible blackspot.

Michaelg, you just got the wrong color cat, lol!!

Seriously, I have an Abraham Darby that's been in the ground since 1982,and has always gotten horrible blackspot; I started giving it Alfalfa meal, and there hasn't been any disease on this rose for quite a while. Don't really know if it was the alfalfa, or just the rose getting older...

OGrose, it depends on what color cat was laying in the alfalfa.

Aw, come on, folks. Obviously you use a black cat to get rid of blackspot.

Admittedly, it only works during a blue moon in leap year, and you have to stand on your left foot for 30 seconds while rubbing your tummy and patting your head and counting backwards from thirty in Portuguese.

Lol, you guys are a hoot!

KIM SAID:
"But inland here, our sun, heat and aridity are just too extreme for oils to be safely used. If the product can be phytotoxic, our conditions will encourage it. Filter the sun enough through fog and other humidity, reduce the temperature extremes sufficiently and they can be quite effective, but definitely not here."

*** Even here, closer to the coast, I've found most of the oils to be a very dicey thing to use. We've seen oiled foliage burn in temps in the high 70's.
Recently, our weather has featured wild temperature fluctuations -- up or down 20 deg in a 24-hour period, making the use of oils really tricky.
For me, in most cases, it's just easier to get rid of a rose that is so troubled.

Jeri

The following is posted tongue in cheek:

Jeri has dalmatian dogs. Jeri has roses. She's had both for a good, long time. Maybe the spots on one keep the spots on the others away.

more seriously:

Or...could it be.....climate matters?

BY GEORGE! I THINK SHE'S GOT IT!

Jeri
;-)

I know that here oils are wonderful for frying zinnias, and that definitely it's a black cat for black spot. I have one for just that purpose.