Betty Boop and Black Spot

I have a Betty Boop that appears to be suffering from Black Spot. HMF does not indicate whether BB is resistant. A couple of web sites recommend removing the entire plant if it gets infected. That won’t break my heart as I’m not all that crazy about BB, but thought that it might be useful in breeding. My real concern is BS spreading to other roses. Is this a problem?

Any one else have this problem with BB?



If you have roses, chances are that your roses will have blackspot unless you live in a climate (a desert, for instance) where your leaves never have water on them for about 6 hours at a time when the temperature is at or above 60 F (approximately).

And there are different strains of blackspot, so that a variety that is apparently resistant to blackspot in one area may be a blackspot magnet in another.

And the apparent resistance of the rose to blackspot may be increased by the presence of other, competing fungi inside the leaves. We don’t realize that the fungi are there, so we think that it’s the rose that’s resistant, but the apparent resistance of the rose is a result of fungal action.

Some people live where they’re able to get by without spraying their roses. Either their roses never have blackspot (maybe in the Mojave Desert) or they don’t get so much that it prevents the roses from blooming normally (or close to it) or that it bothers those growing the roses (whichever is the critical factor).

I don’t live in a place like that. I live in a hollow in West Virginia. A hollow has poor air circulation, and stays damp most of the time. My hollow may be the fungus capital of the universe. A rose without leaves is a poor adornment and an even poorer producer of seeds. Although I am interested in breeding roses which are disease resistant, the breeding of roses requires seed production. So I spray my roses every 10 days or so.

Actually, I fog my roses. I bought an Atomist 1026B (sort of a backwards vacuum cleaner) more than 30 years ago, and I still use it. I can fog all my roses with less than 4 gallons of spray material. The Atomist is still produced. Details upon request.

There are several ways to decrease problems with blackspot on roses, and it’s possible to use more than one.

The first way is to plant only roses that get little or no blackspot. Where I live, that means a few species roses, a few varieties of Knock Out, and some tall-growing varieties, such as Scarlet Meidiland, that have leaves far from the damp ground and from water-splashed fungi.

The second way is to provide a healthy environment: good ventilation, and good, balanced nutrition, something that your roses will have if you treat the soil well and encourage the growth of mycorrhizal fungi in the soil. Excessive nitrogen encourages the sort of growth that is more susceptible to blackspot and other diseases, and attracts insects that feed on lush growth, so don’t pile on the chemical (or organic) fertilizers/manures: too much of one thing or another throws nutrition out of balance.

The third way is to spray the leaves with things which may help the plant resist infection. Harpin proteins (available as the product Messenger from Eden Bioscience, but not registered in California or Montana) are reported to make it more difficult for germinating spores to penetrate leaf surfaces. Biofungicides such as Serenade are reported to prevent leaf infection. If you use either of these successfully, let us know about it.

The fourth way is to spray the leaves with fungicides that prevent the spores from germinating or getting established in the leaf. People have made claims for the effectiveness of a variety of products over the years: milk, Miracid, sulfur, sodium or potassium bicarbonate, and a tremendous variety of other chemicals, some with almost unpronounceable names sold under more pronounceable names. And some of these work in particular locations. Most modern fungicides are variations on the things you may use to get rid of athlete’s foot. In recent years I have used Bayer Advanced Disease Control for Roses, Flower, and Shrubs (link below). It works better than others I’ve tried, and my roses don’t have athlete’s foot. Other fungicides may work better in other places, but I don’t have experience with those.

Some claim that a garden left unsprayed for several years will develop a fungal ecology that makes blackspot a minor problem. I tried that–it didn’t work for my location.

Others claim that all sorts of sprays cause cancer or show a tendency to cause cancer. It’s possible to bring out all sorts of studies that support almost any conclusion about whether these sprays cause cancer or other diseases. My guess is that the cancer-causing effect of carefully applied modern fungicides during one rose season in one person’s garden is somewhat less than the cancer-causing effect of driving a passenger car one mile, or of riding inside a car where many of the materials around you are made of plastic and the air you inhale is filled with trace amounts of plasticizers and all sorts of other cool chemicals released as vapors from the steering wheel, radio knobs, seat and door trim, etc. Alternative means of transportation to get you to a store to buy fungicide might also have their drawbacks. For example, you might be inhaling the air a few feet behind a pair of horses or other animals. There are many trade-offs in life.

Just as you can find lots of controversy about whether you should use fungicides, you can find lots of websites where people offer absolute opinions based on little discernible evidence and no apparent thought process. The ability to put up a website or to put text into a website template is not evidence of omniscience. Don’t believe everything you read. Taking out a rose just because it gets blackspot is mostly not very smart since almost all roses get blackspot. If you want to grow roses, go ahead: grow roses.

Keep Betty Boop if you like it. It’s no more susceptible to blackspot than lots of other roses, so grow it and enjoy it and get out there and sling some pollen. It’s that time of year.



I have had some apparent luck with diluted drugstore hydrogen peroxide on black spot, about 10:1 and hence about 0.3%. It seems to trash the spores and prevent new infestations. I can’t swear that it works any better than any of a hundred other sprays. Fairly cheap, easy, and safe, at least.

Of late I have seen a little blackspot on varieties I thought were immune, such as Old Blush. Maybe new strains are arising and spreading.


Old Blush is by no means resistant in MD, as well as Betty Boop. I tried H202 coulpe years ago too, and thought it somewhat helps to reduce BS. By no means a treatment like modern fungicide, not BS prevention, just a little less BS I thought. I didn’t do any control study, so could be just my impression.


Betty Boop is a great pollen producer and used it on several of my roses but I did not have any luck getting it to set hips and for three years I tried. It did get BS quite often during the summer, and the only product I found to work was the one Peter listed, Bayer Advanced Disease Control for Roses. Peter I don’t think you are living in the blackspot capital of the world because I do. (smile)

Peter: I sure don’t live in the desert. The Oregon foothills of the Cascades are still a little damp. I used the Bayer on all of my roses this Spring and they all look good with the exception of BB. Maybe I missed that one. Any way.It’s good to know I don’t need to destroy it. I’ll see how it goes now that it appears we are in for an extended dry period.

I have used a dilute solution of H2O2 on seedlings (not roses yet) to prevent dampening off and it seemed to work fairly well.

Jeanie: Whether I’m right in my assumptions or not, I’ve been using HMF to look at offspring. My first “real” year at breeding will be to focus spreading pollen on the roses that are proven seed producers. As of yet HMF only lists 2 two first generation and both are from BB pollen. That’s the way I was planning on using BB.

Thanks for the information.


Peter… there’s an opportunity here I feel! You could start a rose trial grounds so we can send all our new seedlings to you for evaluation to acquire a ‘Saprophytic and Pathogenic Organism Resistance Esitmate’ (or S.P.O.R.E. for short )

The competing fungus idea is interesting. I wonder if these beneficial/symbiotic fungi could be cultured and used to innoculate our roses as a means of biologically controlling black spot?

There was a thread awhile back on the Garden Web Antique Roses forum ( concerning actively aerated compost tea or AACT. Ron has a commercial rose nursery(over 10,000 roses) in Petaluma,California. The previous owner had used commercial fungicides on the roses. He switched over to spraying the roses and soil with actively aerated compost tea. The first year was a bit iffy but compost mulch and aerated compost tea is all he uses now and his roses do well and at much less cost for spraying and fertilizing. His midge and thrips problem have also greatly lessened.

Do a search: the thread is, “So when will the jury be in”

He wrote this January 19, 2009 and had been using AACT for 2 years. Interesting reading.

Kis or Keep It Simple is the company where he bought his aerator and buys his compost tea. HTTP Server Test Page powered by although homemade aerators can be made with simple aquarium aerators. Garden web also has a forum on soils and compost where they discuss such things.


PS-Ron’s discussion on using AACT at his Petaluma Commercial Rose Nursery is: So, when will the jury be IN?