Origin of Blackspot

I noticed, when reading of diseases of grape vines, that powdery and downey mildew were supposedly originally from America. Transported to Europe with vine cuttings, in Wardian cases.

I have 2 queries from this:

1/ Can we obtain mildew resistance from American species?

2/ Where did Blackspot originate?

The ‘books’ say that it was brought in via the yellow species (R. foetida?), or maybe it just brought in susceptability to balckspot. I haven’t noticed references to blackspot prior to the yellow introduction.


Have you read Harkness’ book Roses? There is a bit in there about how surprised he was all of a sudden in one year to find black spots on roses after never having had it as a problem. The difference was, as reported in that book, that Britain was cleaning up her air.

I was at the ag library yesterday downloading some rose disease papers and the work that’s being done on Black Spot races and their distribution…insert stick man running around eastern North America declaring “It’s everywhere, it’s everywhere.”

There is also a major effort to develop Rosa roxburghii single fruits as a food crop, which has lead to looking for more of the single bloomed species throughout China. And in looking, they’ve found one with Powdery Mildew resistance that the other strains lack.

(There’a also a lot of work on the multiple strains of PM out there.)

Oh gosh, I’m going out on a limb here but I heard/read somewhere that Blackspot originated in the Netherlands (or Sweden)?

Also, the few true American rose species I have collected seem to be very vulnerable to mildew…but have fairly decent BS resistance.

Yeah, blame us! LOL.


Burst out laughing when I read your comment! Say hi to Timo- he’s taken a long-enough break!

Actually if you think about it, the blackspot resistance of NA roses may indicate that they’ve been evolved to resist it, whereas the Asian species never saw it until they got here. Of course that’s not quite true, but maybe when Asian roses got to Europe. The mildew suscep may indicate that mildew came here from somewhere else.

For instance its really hard to grow selected garden sunflowers in KS because this is the origin of all the diseases, yet the wild ones do just fine. Same goes for many crops. They do best in a new environment until the pest or disease catches up with them.

Japanese beetles represent the opposite effect- invasiveness. But milky spore disease damps them down in PA now whereas when I was a kid 40 yr ago they were kneedeep in traps. I wonder if there’s a virus that kills or attenuates BS or mildew. Probably someone should start looking. There are lots of bacteriophages that keep bacteria in check in normal conditions.

I went to the library today and did some searches in the 1800’s. I haven’t found any references to black spot of rose in the first half of the 1800’s, but the second half has a lot of reports including lists of European countries where it was known. (Anybody know what country went by the name Lusitania in the 1870’s?)

North American reports show up in Ag annual reports when they kept records of what diseases were in each state. For some of these, I have to go back and into the very musty originals at our library.

So far, there haven’t been comments (I’ve got a lot of reading to do) as to one class or group of roses being more susceptible.

Since these are mostly general reports, the info is there for Powdery Mildew and Rust as well.

I am finding that the scientific papers in the 1800s have a much lower pomposity content that the papers of the educated laypeople. Just straightforward science…just right for a hot summer’s day.