Blackspot

General Discussion
1

Just finished a tour through my no spray garden to evaluate roses for blackspot. In the beginning I had a “Blackspot Happens” attitude toward roses, it was something I expected to deal with. Today the only rose I found without a trace of blackspot was The Fairy. A few were almost clean, (ie only one or two leaves on a plant) Schulenfest, Julia Child, Shockwave, Irish Mist, Fellemburg, Gen. Schbakine, Gruss An Aachen, Phaleonopsis, Rosette Delizy, Atocha Gold, Miss Bloomsalot and one of my own seedlings a cross of Dorothy Ives X Othello. If I were breeding for blackspot resistance I would not have much to work with as even the antiques seem to be affected. Last year I had very little blackspot on any of the roses but it was like the Mojave Desert here. I am wondering if the heat and drought from last summer stressed the roses to the point that they are more prone to blackspot this year as a result? I am thinking that some of the roses here may be resistant to two of the three races of blackspot which I will take encouragement in and move forward from that point.

I am sure Natalie can add a lot to this thread.

2

Hi Joan!

I think that you are encountering what Dr. Byrne and I do all the time…

Let me try to explain what I mean:

When we start a new field, we plant lots of roses in several replications. Even though we take data the first year of planting, we know that within the 2nd to 3rd year things are going to start looking a lot worse. Why? Because the disease pressure (Black Spot for our area) is building up. There is literally just not enough of the black spot spores around in a new planting to show you the true disease resistance of the plant.

In a previous thread, I had mentioned something like ‘we think we have something great, then we stick it in the field and in a few years what ever disease resistance we thought we had collapses’… this is what I was referring to.

Even though we may be working with a much larger area than you are, the same hold true if you’ve moved the roses from one ‘spot’ in the yard to another. I seem to remember you saying that you had to pot up all of your roses. If you did this within just the last few years, then you’ve probably built up the black spot spores to a sufficient quantity to really ‘let lose’ -so to speak.

I’ve always been surprised that everyone loves ‘Julia Child’. The rose preformed horribly for us. As a matter of fact, within year 2 of evaluations, it was starting to die because of black spot. (Which just means that it started collapsing A LOT quicker than most roses. The real test is usually year 3 for us.)

‘Rosette Delizy’ was never a strong rose for us, so we really couldn’t evaluate it.

‘The Fairy’ has preformed well for us, but I seem to think that in some areas of the US it does get black spot.

The others we haven’t tested, so I can’t comment on those for you.

I totally sympathize with you, I hit the ‘frustration’ ceiling a lot when dealing with the roses! It’s the small victories that keep me going. For example, we made a ‘Perfume Delight’ x Basye material cross. It was years ago now, so I can’t tell you how many crosses or how many seedlings we got, but the point is that one baby from that cross was MUCH better than it’s black spot prone ‘Perfume Delight’ mother. If I were just looking at the baby, I might think ‘what horrible black spot, I should get rid of that’. However, I just remember the fact that we couldn’t even keep ‘Perfume Delight’ alive because it was so black spot susceptible. The baby only has a few thorns, is moderately susceptible to black spot, but has a WONDERFUL fragrance. So, it’s a step in the right direction.

I believe it was Mr. Moore who said ‘the perfect rose is the one I haven’t created yet’. There’s lots of things he told me that help keep me going. You could also take the attitude of Dr. Byrne who get’s excited when he see’s black spot. Yes, we all laugh at that statement when he makes it, but he is quite serious. He always jokes that it’s job security!

Just keep plugging along Joan. I’m sure you’ll uncover a real gem!

3

Natalie,

Thanks for the encouraging words. What you said makes sense because this is the second year in pots for most of my roses. I have just recently started to be concerned about breeding for blackspot, my efforts have been rather helter skelter so far, mostly I prefer roses with lots of petals and good fragrance, in that regard I have had some success. I have no illusions about creating a “Knockout”. I guess I really like Mr. Moore’s “why not” attitude when deciding what crosses to make.

I am surprised that Rosette Delizy did not fair well for you, mine has been in the ground for 8-10 years and routinely grows to 7 ft., however it is in an area that is fairly shady.

4

You could also take the attitude of Dr. Byrne who get’s excited when he see’s black spot.

I personally love it when PM starts every year. At least on my seedlings. I do not have a great amount of room for seedlings and it lets me make a quick judgment on what to keep and what to put into the compost pile. I may keep some that show it only a little but the worst offenders are thrown out.

5

Exactly what I was thinking Adam!

Here is a picture of what I saw in the greenhouse today:

[attachment 456 PMexample.jpg]

These are the ‘selection events’ that make my life easier!

6

You’d think so, but very often, those which have shown mildew under greenhouse conditions, especially as such young seedlings, have developed into mildew free adults and produced mildew free seedlings. If they still mildew outdoors, that’s something else entirely. Don’t work with Banksiae. I seriously doubt it’s possible to raise a mildew free Banksiae seedling.

7

http://www.ulmer.de/Artikel.dll/ejhs-14-07_NTM5Mjg3.PDF] [/url] Early selection for powdery mildew

In the protocol this article describes,I interpreted that garden roses are not really mature enough to select for powdery mildew until shortly after their first bloom, because they are still in their juvenile stage, and have not built up enough resistance. Because of this, I have been only culling the most stunted, deformed and runty ‘diseased and failing to thrive’ seedlings. I am noticing that many (not all) of the formerly mildewed, but not runty or deformed, are now starting to grow new foliage which is quite clean and mildew free.

8

That’s what I’ve seen from my own and the bazillians I observed over the years at Sequoia. Who knows how many potentially good ones have been prematurely culled?

9

At least the repeating seedlings do not get planted out until they have bloomed twice for the most part. I first only cule out the very worst ones. Their are still ones that get planted outside that still get mildew. If they still mildew outside they get pulled.

10

Sorry guys, I have to respectfully disagree here. When the baby is so white that I can’t see the green of the plant, it gets pulled. A little PM I can live with, but this is well beyond my tolerance for disease.

My experience has taught me that if I don’t go ahead and pull it, it WILL die on its own…

Especially note the fact that the siblings around it are in a much better state of health.

Jackie and Kim,

I haven’t read the article in depth, but it’s a good start. A lot more work needs to be done before any real conclusions can be drawn. I’d like to see the experiment repeated by at least 2 other (independent) labs. Right now, the biggest problem I have with that article is the small number of progeny studied. For a truly powerful statistical study to be done at least 100 babies per cross need to be studied. From my own experience, you’d be surprised at how much the results will change once you get enough seedlings to study.

11

Mildew is so rare here that if I see anything like what Natalie shows, it’s gone. And fortunately we don’t get B.S. until they’ve at least bloomed. So I cull based on whether the flower looks good. Then I usually plant in rows at a density of about 8/ft of row in rows a ft apart. What survives “neglected” for a couple years is what I keep. Unless the flower really strikes me in which case I may pot it up to see how the reblooms come out. Winter is a geat selecter (or was until this year).

12

It reallydepends on the group of seedlings if they can outlast a pm attack. PM seems to act like algea bloom and runs it`s course. Had seedlings with sever PM and after iwo months a cane 42inches tall and clean. Another group all had PM so I looked at the mother plant, some popular rose planted all over, and it had some PM.

13

Kim wrote: Don’t work with Banksiae. I seriously doubt it’s possible to raise a mildew free Banksiae seedling.

I fully support this affirmation. Lutescens or normalis self pollinated/OP seedlings I raised more than once years ago where consistently in the seedling trays white whoolly and distorted from PM. A soon as set in ground and full sun PM disapears without any chemical all seedlings behaving like the typical species.

Rust that is rare in my greenhouse can first autumn heavily contaminate some progenies i.e. foliolosa x rugosa to the point plastic mulch is painted orange and never be noticable in the same plants at same place for following years.

Reversely in a well tended greenhouse BS is rarely occurring and early selection impossible.

Most banksiaes are not PM resistant only very tolerant. It is horizontal resistance. Selecting seedlings early can be damageable for horizontal resistance breeding.

Reversely also there are progenies: i.e. HTs and lot of garden tetraploids that in my conditions are in and out quite consistent at desease susceptibility.

14

Despite Pretty LAdy being bred in a wet, temperate climate, it seems to take summers better than most other roses. It’d prolly do okay in Texas. It has been blackspot resistant for me for every year it has been here since it was introduced. Livin’ Easy is better than most, but not perfect. However, it is a good source of orange in a decent plant. I dont think it is a heat-lover though.

15

[quote=PacificJade]

Despite Pretty LAdy being bred in a wet, temperate climate, it seems to take summers better than most other roses. It’d prolly do okay in Texas. It has been blackspot resistant for me for every year it has been here since it was introduced. Livin’ Easy is better than most, but not perfect. However, it is a good source of orange in a decent plant. I dont think it is a heat-lover though.[/quote]

Actually, it does horribly here. It won’t survive unless you protect it from black spot. :frowning:

16

I was about to say what Pierre beat me to saying.

Natalie, in our climate, I cannot think of a healthier rose than banksia, yet from all that I have heard and read, you will not find a seedling that isn’t highly susceptible to mildew in its infancy. I fully intend on working with R.b.lutescens quite heavily, personally, if she ever blooms at the same time as something I wanna cross her with. I cannot think of a healthier rose. Period.

Larry, don’t gloat about your lack of disease. It might make you unpopular here. :wink:

17

Not unpopular, but the USPS would probably come after ther rest of us for the many envelopes dripping with white powder, orange powder and black spots…hehehe

18

[quote=Philip_LA]

I fully intend on working with R.b.lutescens quite heavily, personally, if she ever blooms at the same time as something I wanna cross her with.[/quote]

The way I work with most once bloomers is to treat them as pollen parents. I collect as much pollen as I can possibly get my hands on (from the once bloomer) and store it until I need it. Usually, I will use it the same year I collect it, but some are quite late blooming…

If you don’t have a favorite method of storing pollen, let me know and I’ll tell you how we do it.

The PM issue:

Thankfully, we currently have no desire to use banksaie in our breeding!

19

There are a couple of suggested methods of storing pollen I’ve run across, but what do you find successful, Nat? I bought the silica gel packets and have a seal a meal I can use, but “better late if ever” takes over and it just doesn’t get taken care of.

20

Nat, can you share with us/me your method of storing pollen, it might/will come in handy down the track for me, thanks.