Immediately after spraying:

Here's a newer 2013 study on soybeans, "Essential oils and whole milk in the control of soybean powdery mildew": http://www.redalyc.org/articulo.oa?id=3312877800

Fantastic experiment! Thank you for posting pics. I would love to see the end resuit. Dr. Henry Kuska posted on how fatty acids help to control mildew.

Thank you, prairie_north, for that link on essential oils and whole milk in controlling mildew.

Gruss an Teplitz, the father of Dr. Huey, is a mildew-fest (even in good potting sol). I fed Gruss with WHOLE-GRAIN corn meal (with fatty acids) .... mildew went away. I like that so much, so I dug Gruss up to put cracked corn in the planting hole. It has been 3 years, and zero mildew on Gruss. It's in partial shade, less than 5 hours of sun.

After about an hour or so later, most of the milk is dry and the leaves certainly look better with less of the white dusty appearance:

How bad is PM in your area prairie_northrose? I've heard of other people having good luck with spraying milk on rose leaves for PM so hopefully you do also! :-)

I has zero issues last year, but this year some as its been a pretty wet year, rainly on a weekly basis from May through August and into September (very rare).

6/6 of my Winnipeg Parks bushes have 25% of leaves with it, and I have one Champlain bush had over 75% leaves covered in powdery mildew.

Both these varieties are heavy flowerers so perhaps it may also have something to do with the overall health of the plant. It may also have something to do with the fact these roses were planted this year, and had originally arrived from Vancouver B.C. where I assume PS is more prevalent with the more humid weather.

But again good luck with the milk....

Hopefully next year the PM problems are not as bad for you...

Prairie_north: YOU ARE RIGHT about "Both these varieties are heavy flowerers." Dr. Henry Kuska noted that roses break down with diseases RIGHT AFTER HEAVY BLOOMING, due to depletion of potassium. Potassium is a nutrient needed for blooming and disease-prevention.

My Tchaikovsky is clean, until it's done with a heavy flush (15 zillion-petals blooms) .. then it broke down with mildew RIGHT AFTER HEAVY BLOOMING, due to depletion of potassium. I gave it sulfate of potash, and the mildew lessened considerably.

I also have Dreil de Raynaud ... known as mildew-prone. it gives zero bloom this year, so it's 100% clean. Roses are clean until nutrients are depleted through blooming, esp. potassium & calcium and trace elements. The same trace elements needed for blooming: zinc, copper, and boron ... these are also strong anti-fungal agents.

Straw wrote: " Dr. Henry Kuska noted that roses break down with diseases RIGHT AFTER HEAVY BLOOMING, due to depletion of potassium. Potassium is a nutrient needed for blooming and disease-prevention.

That's true. I also experienced the same. Not PM but BS and other fungal diseases. BTW, I saw a few pics on the net of roses with over 150 blooms on one bush (not ramblers or once flowering roses) which was planted in a 12 inch pot. The bush looked enormous compared to the size of the pot and had more flowers than leaves perhaps. I wonder what would have happened to those rose bushes once they were done blooming.

Straw wrote: Gruss an Teplitz, the father of Dr. Huey, is a mildew-fest (even in good potting sol). I fed Gruss with WHOLE-GRAIN corn meal (with fatty acids) .... mildew went away. I like that so much, so I dug Gruss up to put cracked corn in the planting hole. It has been 3 years, and zero mildew on Gruss. It's in partial shade, less than 5 hours of sun.

Now that's a surprise for me that Gruss an Teplitz also gets sick. Gruss an Teplitz is like a wild rose here and actually very few people know that it was bred in Austro-Hungarian empire. The local name for Gruss an Teplitz is "Desi Gulaab" which literally means "Native Rose". Quite a few people believe that Gruss an Teplitz is a native rose specie. It is also used as a root stock for grafting roses. As for it's performance, it's an amazing performer in Pakistan, India and Bangladesh. People don't feed it, don't even water it often, plant it at the worst possible location (where no other rose would survive) yet Gruss survives and grows well, giving tons of highly fragrant blooms whole year round. The traditional garlands that bride and bride groom wear on their wedding are made of Gruss an Teplitz. It is traditional during formal visits and festivals to sprinkle rose petals on the guest of honour on his / her arrival and the petals are of Gruss an Teplitz. Even on funerals, coffins are covered with petals of Gruss an Teplitz; so are the graves in the grave yards. It's used in various cuisines for flavour. It's essence is used as a perfume. I wonder what we would have done without Gruss an Tepltiz. Thanks to British who brought it to India in early 20th century. And Gruss an Teplitz getting sick........ never heard of it earlier.

So much for a legendary rose

Thank you, Khalid, for a wonderful story of Gruss in your country. I enjoy that. My Gruss an Teplitz has RMV (rose mosaic virus), the nursery gave me that for free, I didn't have to pay. The lowest leaves look like the below, picture from Heirloom rose nursery on RMV. RMV is a problem in American nurseries, which propagate roses through cuttings. My Gruss is very drought-tolerant on its 3rd year, and the RMV is lessened through the years .. I have Gruss in a bad location: shady and rock-hard-clay on a steep hill, with very little sun in our cold zone 5a.

Yes, I once bought such pot from HomeDepot: at least 60 blooms on that rose with many petals. When I took the rose out, it's a slightly acidic, fluffy, loamy, airy, VERY LOOSE medium with composted pine-fines, peatmoss, and blue-slow-released granules. When it finished blooming, that didn't break out in diseases since WE WERE IN A DRY SPELL. But if we had rain, that would result in fungal diseases since RAIN LEACHES OUT POTASSIUM, CALCIUM, MAGNESIUM, AND TRACE ELEMENTS ... all needed to keep the leaves on roses.

The best way to prevent that is to put a THICK LAYER of buffer on top, so rain would break-down that "buffer-layer" to release nutrients from above. That's much better than rain "break down" the root-zone, and hurt roots with acidity (pH of rain is 5.6). I achieved 100% health in roses right before winter, which I posted in Sam's thread "Organic treatments for roses: what worked, what didn't work?" I did that through "buffers on top" which has the perfect ratio of nutrients for roses (equal nitrogen to potassium, 1/2 calcium, and 1/10 magnesium 1/10 phosphorus, plus trace elements). I put 3 buffers: alfalfa-meal with NPK 2-1-2 first, chicken manure plus sulfate of potash NPK 5-3-5, and horse manure with lime on top with all the trace elements.

I have 3 rain-barrels which I tested on roses by routing the overflow from the roof: dumping 32-gallons of rain-water on each rose in one-hour time-frame. Evelyn was 100% clean before "rain-dump", broke out in BS after 24-hours rain, plus many gallons of water dumped on. The only rose that stood that test was Stephen Big Purple, which I topped with a thick layer of alkaline clay mixed with organic-fertilizer.

I tested pea-gravel and red-lava-rock as buffers against acidic rain. The result? NOT AS GOOD as the triple-layer of alfalfa meal (pH 5.8), organics, and limed horse manure (pH 8). Pea-gravel and red-lava-rock blocks out the rain, so water can't go down, plus the pH is too high, and the nutrients-release is too slow and too little to offset heavy rain.

Purdue University had a research which showed MULCHING with mushroom compost (limed horse manure) is best to stop artillery fungus, which shoots up black-spot on sidings of the house. Another University Extension did a study on buffers against acidic rain, which showed lime is the most effective buffer to neutralize acidic rain (pH 5.6).

Is your Gruss an Teplitz grafted? In Pakistan, all Gruss an Teplitz are own root. Actually, here one just needs to put a cutting from Gruss in some kind of soil and water it couple of time and it will sprout. I will post a few pics of Gruss an Teplitz grown in the fields for commercial use. It's a great sight to see millions of them on many acres of land.

I would suggest you grow it own root and I think you will have no problem with your GaT. Or may be GaT is not a good performer in cold regions. But it performs very well in Pakistani cold region up to zone 3 (if protected during coldest period). But since all of them are own root, they grow back in summers.

My Gruss is OWN-ROOT, but some own-roots can be infected with RMV (rose mosaic virus) here in America. Jim bought an own-root Earthsong rose (has RMV) and he had to kill it, since it's always sick.

Pakistan has a healthy version of Gruss, we have a virus version, and that virus replicate with own-root-cuttings. Thanks, Khalid, I really should move my own-root Gruss to full-sun.

Ah.... didn't know that own roots also get RMV. I always thought it comes through grafted stock (Dr Huey etc).

Khalid: Most of my 50+ roses are own-roots, except for recently bought Pink Peace and Lavender roses. Lavender Rose, grafted on Dr. Huey, really likes the pea-gravel (pH 9) mixed with my clay soil (pH 7.7). Pink Peace blackspot badly with alfalfa pellets (pH 5.8) mixed with clay, but it improved in health when I gave it slow-released dolomitic lime (pH 9).

Dr. Huey-root-stock likes it well-drained & alkaline, very popular in hot & dry California.

RMV (Rose Mosaic Virus) is not the name of a specific virus, it is a group name for viruses that exhibit mosaic symptoms when they infect roses. Descriptions of many of the various viruses that infect roses (along with other rose virus information) can be found at:

https://sites.google.com/site/rosevirusindexpage/

Thank you, Henry, for that link. I'm glad you dropped by.

I sprayed a second time. Then it got cold (-6 Celsius), so my test result are not as valid as I would have liked. Most of the rose leaves are now dry from frost damage.

The sprayed leaves have a white residue (I presume the milk fats) that easily wipe off. There appears no powdery mildew underneath:

The unsprayed branches still have powdery mildew, the mildew is difficult to wipe off:

Here I try to wipe it off, beside my thumb:

I'll give it a try again next year to ensure the results I am seeing is from the milk spray itself, and not the cold weather.

Yes it is hard to know if your getting good results this time of year for sure...

I rinsed off the residue with water. Here is the sprayed branch that did best and photographed well, this is the same branch from the second photo from the top of this post:

For comparison, here are non-sprayed leaves that were (and are still) heavily infested with mildew at the same time, about four feet to the left.

I would be curious to try soybean oil one day, it sounds effective as indicated in the study in the original post.