The American Rose, page 27 (October, 1976)
BLACKSPOT RESISTANT ROSES
By William J. Radler
Assistant Garden Director,
Alfred L. Boerner Botanical Gardens,
Hales Corners, Wisconsin.

Because I have been recording blackspot resistance for the August Peter Memorial Rose Collection of the Boerner Botanical Gardens since 1972, I felt I should comment on Asa D. Tupper's article in the January, 1976, issue of this magazine, titled "Some Do, Some Don't." He and I seem to have some conflicting data on blackspot resistance which I thought should be brought out. Roses which both he and I reported on are listed as follows:

Rose (Tupper)
Resistance
(Radler)
Resistance
R. palustris Resistant Resistant
R. blanda Resistant Resistant
R. spinosissima Altaica Resistant Mod. resistant
Karl Forster Resistant Susceptible
R. x harisonii Resistant Susceptible
Stanwell Perpetual Resistant Mod. susceptible
Rose a Parfum de I'Hay Susceptible Susceptible
Frau Dagmar Hartopp Resistant Resistant
Flamingo Resistant Susceptible
Therese Bugnet Resistant Resistant
Conrad Ferdinand Meyer Resistant Susceptible
Nova Zembla Resistant Susceptible
Zweibrucken Resistant Susceptible
Tuscany Not reported Resistant
Tuscany Superb Resistant Not grown
Mme. Isaac Pereire Resistant Mod. susceptible
R. centifolia Resistant Susceptible
Alika Resistant Susceptible

Since many of the roses he listed as blackspot resistant I listed as susceptible, I wonder if Boothbay Harbor's climate is less favorable for blackspot, or if more years of observance his part would have brought about different results.

Besides the above roses, several others have shown blackspot resistance for me: Agnes, Applejack, Hansa, Banshee, Belle Poitevine, Blanc Double de Coubert, Konigen von Danemark, Lillian Gibson, Eddie's Crimson, Wasagaming, Schneezwerg, R. gallica officinalis, R. gallica versicolor, R. setigera, R. hugonis and R. eglanteria. It should be understood that all these roses have been grown in the open. In the shade and/or in a confined situation, resistance to blackspot might be expressed differently.

Besides observing resistance to blackspot, I also made observations on the effect of winter on blackspot susceptible plants. Odd as it may seem, there were two types of reactions. Take the two roses, Nevada and Alika, which are normally hardy. Nevada died back to the ground over winter when blackspot wasn't controlled. Alika was hardy to the tips even after a year of blackspot. After seeing this phenomenon, I can see why some people say that blackspotted roses will suffer winter injury, and I think this is the case with most of the modern bedding roses. The once-blooming old garden roses, however, usually will behave like Alika and not have winter injury, even though they were defoliated in late summer by blackspot.

For those people who can't spray or will not spray because of ecological reasons, blackspot resistant roses are the answer. Perhaps some other people have had experience along these lines and can add to the list?