Blackspot on Roses
How to deal with it in established rose beds

Q: I have a 10 year old rose bed with approximately 45 - 50 roses. I am really disappointed with their performance over the past couple of years. The blackspot, even with regular sprayings of Ortho Funginex, has been impossible to control. My bed sets in direct sunlight until around 5 p.m.

Last year I tried to make sure that every affected leaf was removed from the entire bed. But my efforts seemed to make no significant difference. After reading the information on your web page, I have found that I may have already done some damage. I trimmed my plants rather severely about 2 weeks ago which is the time I normally trim. But this year, due to the mild winter, instead of dry canes the bushes were leaved out. The leaves were very small, and canes didn't look like bud producers.

Assuming I haven't permanently damaged a rather time consuming affair, what should I do next?

A: Thanks for your question concerning blackspot control for your roses. Blackspot is one of the most distressing disease's that we rose growers must face. Blackspot is a spore that develops in the ground and can spread from one plant to another plant. The beginning battle with this spore is to start spraying a fungicide once the buds become pea size. Funginex is a good to moderate protector but because you have already had the spores set up home in your rose bed, a stronger product may be necessary. Banner Maxx and Compass provide good protection and will last longer. A very important method to preventing blackspot is to remove foliage that is within 6 inches of the ground. The spores splash up from the ground and attach to the leaves when it rains or when you water. This will help in establishing more basil breaks and should be done by the later part of May this year. Once blacksot is spotted in your rose bed I would recommend using Daconil to destroy the blackspot spores. However, this product will take away from the plant somewhat because how it works.

The roses that you cut back will come back later this spring. However they may be later than others. You can begin applying Monty's Joy Juice once you have new foliage that has turned green.

Q: All of my roses, although they have not come out completely yet, already are showing blackspot. Should I go ahead and de-leaf the plants from the ground up 6 inches and spray with Daconil even before they bud out? You said that this application will take away from the plants. How so? And this year I have mulched with pine needles. I was planning on leaving them in for summer mulch as well. Is this a good idea?

A: I would not remove any foliage at this time. The plants need as much foliage as possible. If you really have blackspot then you can spray Daconil now. The Daconil product seems to slow growth during the hot part of the summer. Please check the leaves that appear to have blackspot. Determine if the leaves have spots on the back side as well as the top. If the spores appear to be on the back side and you see a purple tint you may have iron toxicity.

Pine needles work ok provided that you add more once the average ground temperatures remains around 75 or above. The pine needles sometimes thin out during the summer, thereby allowing the ground temperature to warm and this makes the roses go dormant such as it has during the winter.

Q: I've enjoyed your site, and found it to be a valuable source of information! I set out to learn more about blackspot and how to control it, and found your section of "how to deal with it in established rose beds" to be very helpful. My question is about Daconil. You recommended that it be used to destroy the established spores, but said that it "would take away from the plant somewhat because how it works"...what did you mean by that? I've got my first outbreak of blackspot, and I'm very frustrated with it. My garden is two years old now, and I have really enjoyed my roses, but the blackspot is not fun. I want to kill it as swiftly as possible.

A: The Daconil product is wonderful on black spot spores. However, the Daconil will inhibit the growth of the plants when day time temperatures and night time temperatures stay above 80 degrees. The Daconil leaves a film on the leaves and this causes the plant to lessen it's ability to transpire the needed CO2.

If you have any questions please e-mail me if you have any more questions.

Dennis Stephens