Sammy, just because there is moisture on the leaves does not mean that the plants themselves are hydrated. Maybe you have had more rain than here but we are way behind annual rain. Nothing has worked here this spring to control the PM..not even all the stuff that is supposed to. Cass said something in another post that made sense to me..the roses are so stressed from that late freeze that we are seeing things that we don't usually have happen here. I'm just keeping up the regular spray program and even the local nursery on TV made the remark about the stress and the need to keep the plants hydrated. To me, with the lack of rain, it means water..water..water. Maybe we will get some rain out of this front coming thru..

Then too, We found when we sprayed that there were some roses that mildewed no matter WHAT we sprayed. In the end, those few roses weren't worth it.
In the long haul, you may find that is true of some of your roses. Once we removed the "bad apples," things got a lot easier.

Jeri

Kaye, once again thank you so much. I don't need to stop and spray since I have so many other things to do in the yard. It looks like all the rains have just moved past us, and have left us dry once again. I will go ahead and wait out the week if I can. I hate it that i spent so much for the Conserve to have it only work for a few days.

It is like you say, they are stressed, and that is the real problem.

Jeri, I whole heartedly agree with you. I will not have Disneyland, and quite a few others since they have so many problems. However, mildew is rarely a problem here. I usually only see it on Crape Myrtles on the side that never gets sun. Blackspot is our problem, and it has not improved.

What a year!
Sammy

Yeah, east of the Rockies, we probably shouldn't give much weight to mildew in selecting roses. Maybe in the Maritime Provinces, but not here. Here this season we have more PM than usual because of the drought.

Sammy, it's not the lack of mancozeb. I don't think mancozeb is considered a PM control.

I know Kaye successfully sprays Banner/mancozeb with Wilt Pruf, but I've wondered if it would prevent the systemic from being absorbed into the plant.

That is a good point, except that I, too have used the Wilt Pruf for a few years, and have never before had this problem.

One of my newest roses that has been struck by the powdery mildew is Clair Matin, but the others have never been affected before.

I think that the roses are proably under stress, and I will wait.

One problem is that the freeze affected so many roses, that I thought it would be better to wait to cut them back. I thought that they could benefit by the photosynthesis, and better grow new basil canes, if I delayed pruning them. I realized at the time that I could be exposing them to canker that could have set in when the freeze and thaw caused the canes to split. Now I face the prospect of having to try to get into the roses and trim out the bad stuff. I am hoping that the canker fungus has not spread to the new growth.

I wish I were a horticulturalist. (Gee I wish I could spell that word.)

Michael, you are truly an expert, and I appreciate your suggestion about the Wilt Pruf. I am going to see what happens in the next week or so. I did think Conserve would work for two weeks.

SAmmy

Here this season we have more PM than usual because of the drought.

*** Well, that would fit with it being a common problem HERE, (where drought is a constant spectre) and rarely THERE.

Jeri

Sammy, I'm sorry your roses are suffering through a tough season. I had a lost season a couple of years ago. It happens, Nature's way to convincing us we don't need to grow any wimps. Banner Maxx is labelled for blackspot, powdery mildew and rust in roses. It should be working as well as anything.

We tend to think of rose fungal disease in a very simplistic manner: my rose is exposed, so it gets the fungi. Speaking from the perspective of a rose grower in a region with little blackspot, I doubt it, article in the American Rose magazine about spreading BS with a leaf blower notwithstanding.

My garden has seasons when powdery mildew is bad, seasons when rust is bad, seasons when botrytis is bad, even seasons when blackspot is somewhat bad. The next year, the very same rose will be clean with no spray intervention by me. Although the weather varies somewhat, it isn't so wildly variable that I think that present temperature conditions alone could account for the differences. Soil and water are constants. So how do we account for disease pressure in the garden?

It is multi-factorial, not simply exposure, but also the relative strength of the plant's own built-in immune system, present weather conditions and even weather conditions are some critical stage in the development of the rose or of the fungal organism. This is why I no longer lose sleep if someone complains that a rose I'm interested in suffers from this or than fungal complaint. Roses that have never shown one second of powdery mildew in my garden mildewed extensively in a Southern California hybridizer's garden this spring. IMO it doesn't mean the same roses will ever get PM in my garden or even that it is genetically disposed to PM. I've seen young plants suffer PM and other fungal complaints in pots that, after being planted out in the garden and mulched with 3 inches of bark, never showed disease again.

There are good years and bad in the rose garden. Sometimes only time is the cure.

I think you are right. We will cope this year, and hope for a better season next year. Above all, I need to water and fertilize. Sometimes it is not easy to get to all the roses.

Sammy

Here's an example of the "built-in immune system." Colette has never shown a speck of black spot in maybe six years. In the Easter freeze, its new growth was all damaged but mostly not killed, and there was too much of it to pick off. It's a dense pillar about 6-1/2' tall with a snarl of canes. A few weeks after the freeze, black spot popped out all over the plant, nearly 100% of the damaged leaves. They did not have the normal ability to resist.

Now, black spot is not very mobile, moving mainly through splashing water and the gardender's hands. This result showed that black spot was already there, all over the plant, and never visible on the leaves because Colette wouldn't let it express the spots! It could only have spread to the damaged leaves from tiny lesions on the old canes that have been building up over the years. I don't expect to see it on the healthy foliage, although it has been so dry, I can't say for sure. We have had a few spatters with overnight wetting lately, so if it is going to show, it should be noticeable a week from now.

Well, from PM central I can report that the temps in the upper 80s and low 90s seem to be knocking the PM down. It was so bad that I didn't want to breathe near the bushes.
Our drought continues with a 13 inch deficit on barely `10 inches of rainfall.
The unintentionally unkindest cut came today when I mentioned to a neighbor that I was glad to have a well for watering and she looked at me and asked, in total innocence, "Have you been watering?" Duh, yeah, or the roses would be toast already.

So, any predictions about PM this fall with the gadzillion spores out there from this spring's disaster?

I began seeing lots of mildew in my garden 2 weeks ago. Some of my Austin rosebushes (Heritage and William Shakespeare 2000) looked like this:

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I Sprayed 2 times with Fertilome Systemic Fungicide and every day I removed the worst affected leaves. It has kept it down as much as possible. This morning they looked like this...lots of buds and they will bloom in about 2 weeks from now:

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I think it was the very hot days and the very cold nights with lots of dew that gave optimal conditions for the spores to spread. I keep my plants well watered so it is not caused by drought. Mildew is usually only a problem in the fall when the hot days/ cool nights comes. But this year it started early, even though I watered and sprayed to prevent it.

So I will suggest keep removing the affected leaves and spraying more often. It keeps it down at least. But next time I come to US I will buy some more sprays from rosemania.

I wonder if there is anything I can use to spray the rosebushes with in the fall, limesulphur...bourdeaxmixture? after the rose has dropped their leaves, to kill the spores overwintering on the canes.

I also took pictures that showed what Powdery mildew looks like for the website I work on:

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"A few weeks after the freeze, black spot popped out all over the plant, nearly 100% of the damaged leaves. They did not have the normal ability to resist."

I had not considered this at all Michael, but it totally makes sense now that I look back on what happened to my roses this season too. One of my Belinda's Dream nearly went foilage nekkid from BS, which totally blew me away. PM has been hit or miss on various OGRs and HTs- but it seems to be the ones that were least protected from the freeze.

Nancy

You can witness this yourselves. Remove some leaves from a blackspot resistant rose. Lie them on the ground under a rose with blackspot. Assuming the weather isn't so hot and dry that the leaves dry up, I'll bet the BS-resistant rose leaves get blackspot before they die completely. The same is true of rust. That's why so many gardeners see blackspot in the fall when their roses are going deciduous. BS is ever-present. The foliage is being killed off by the rose. Specifically, the rose may reabsorb certain nutrients from the leaves, leaving them less disease resistant.

Thanks, Cupshaped, for the pictures. Beginners should notice the leaves showing their undersides-- this lets you spot PM from a distance before it even produces the white stuff-- although older leaves that have stiffened up usually won't show that.

Fertilome Systemic is propiconazole, same as Banner and Bonide Infuse. It seems to be as effective as anything. I read a disturbing study the other day that found even the best fungicides ineffective when rose plants were already heavily infected and conditions for disease were optimum. So picking off infected leaves and stems makes sense in that context. My primitive sulfur fungicide has done nearly a perfect job of preventing PM this year, except on the no-spray roses that don't get blackspot, and which now are getting sprayed. Sulfur is widely used in agriculture for PM, so it is effective, but only as a preventative.

Drought doesn't cause PM, but rain twice a week goes a long way toward preventing it. I washed down my roses this morning before spraying. PM germinates only on dry leaves at very high humidity, with temps mainly in the upper 50s and 60s F. These conditions occur mainly at night when the temperature holds for a few hours just above the dew point. Fog and heavy dews suggest PM conditions. PM is unlikely to germinate if the dew point is below 55, or if night temps are above 71, because dew points above 70 are pretty rare. Daytime temps in the 70s-low 80s are ideal for mycelial growth and release of spores. As Ann says, it doesn't like hot weather much. (from Horst's Compendium of Rose Diseases)

So no rain = pm. Well now it makes sense. I have it on some of my roses, but I always seem to have it on some of them. This year, I'm seeing it all over the place, especially on my crazy daises that took off this year. I divided up two clumps last year and planted them all over and was delighted to have these bright white spots all over the yard. But the foliage looks terrible.

We had some rain last night. But I watered anyway. Can't tell when it will rain again.

We are now 36 days with no significant rain, just three or four evening spatters, enough to get botrytis on some of the first flush. All the moles on the hillside are plowing around my garden because, everywhere else, they kept breaking their fingernails.

You may want to spray with milk solution on a few roses to see if itÂs effective there. 25% works well for me. I had a small outbreak on Arethusa and some HTs in this drought, starting with Dorothy Perkins who routinely gets PM every year no matter what.

The recipe I saved calls for 10 to 15% part skim milk, but I just use regular milk and a quarter of it is easy to measure.

My next door neighbor who, like me, grew up gardening and learned a lot from her mother and older ladies told me to water my roses the day the chlorine was put into the water to help with the powdery mildew. I am not sure that has helped or if it was the 70+ nights we have had in the past week but something has helped, maybe both.

On Saturdays our water is heavily chlorinated, so I chose that day to water.

Michael, thank you for your example with Collette. I think you are correct, and am pleased that I am not being encouraged to spray more.

Ann, I predict not much PM in the fall here. Once our high temperatures set in by July, it will burn up all the spores, maybe. ha ha!

Cupshaped roses, you live in Denmark! How interesting. Do you come to the US often? And you grow the same roses in Denmark, and have the same fungi.

Nancy, as you and others share, I do feel better even though I am sorry that your gardens have endured the same trauma as mine.

Berndoodle, are you sure about that? I thought the black spot would not spread on the ground. Are you saying that it is the black spot spores in the air under the other roses or the ones in the ground?

Michael, that is why we don't have the problem that others do. By July our night time temps remain around 90 or above.

Buford, I am with you on your Daisys. My blue salvia has it. I feel like they are innocent victims. That is a real insult.

Roseleaf, won't milk solutions draw ants or other critters?

Patricia, that is interesting about the chlorine. I think I will call to see when it is added here.

Michael, the gohper fingernail thing is a riot. I hate those critters, and they are everywhere here.

Sammy

Pretty sure, Sammy. Blackspot overwinters in leaf litter and on canes, not in the soil. If the weather conditions and cultivar selections aren't conducive to the germination of a large number of spores, it doesn't get a foothold but that doesn't mean it isn't there. IME it is everpresent at a low level whereever there are garden roses. Spores are spread by water splash and by wind-borne leaves. It probably comes in on the roses we buy, and it likes the same conditions that roses like. Maybe your garden sanitation is much better than mine so there are no leaves on the ground. With hundred of roses, I always have leaves on the ground, in the air, in my pockets, in the gutters, in the mulch.