From the following photos, you’ll see that we’ve been battling (and not winning the war) with blackpot on our roses since I corresponded with you previously last year. Our gardeners have been applying monthly treatments of Cease to try to eliminate it but it hasn’t really improved. I was wondering if you might have any other recommendations for a more aggressive treatment of the roses to try to eliminate this fungal pressure on the roses.
Here are the photos that I took yesterday to demonstrate the issue for you:
As always, I welcome your thoughts and recommendations. Thanks tremendously for your help!
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I feel your pain. If you live in a region where blackspot is an occasional problem, then Cease may be somewhat effective, however, organic controls of blackspot are not as effective in preventing blackspot as are chemical fungicides. If you do not want to use chemical fungicides, then look at some other products that might help. For example, Magic Gardener which is a newer Bacillus, however, you will need to rotate with another bio-fungicide. And it absolutely must be applied before any outbreak of the disease. And such applications must be done weekly. Spraying Silicone, like Super Thrive’s ProTek and products with extracts of Thyme, like Thyme Guard will also help. For sure you should add a product like Maxicrop every time you spray.
Now, since I spray rose gardens as a business, I always combine a contact fungicide, like Daconil (in spring and fall) or Mancozeb, with a systemic fungicide, e.g., Myclobutanil or Propiconazole, and every few sprays add Azoxystrobin. There is a synergy with this combination of fungicides. I do use a spreader like Indicate 5 and always add Maxicrop. This keeps my clients rose leaves black spot free, except for roses that are extremely blackspot prone.
Rosejoy, when do you start spraying, and how often during the growing season? I’m in Kennesaw, Georgia, just 35 miles NW of Atlanta, so we have lots of humidity to deal with. I moved here from Las Vegas (the Desert!) and have already shovel-pruned 6-7 roses, mostly David Austins, that were BS magnets. I have also replaced 4 older roses that weren’t disease resistant at all. Hopefully, the worst is over, and I can start a normal spray program and stay ahead of the BS! (appropriately titled!)
Thanks,
Jill Barnard
“Rosejoy” – Thanks tremendously for your notes here. I’m certainly not wed to organic products, so I valued the details of your approach here. We have a grape vineyard in addition to the 250+ roses on the property, so I’m a licensed pesticide applicator. From your notes, I’d value your comments on this approach when we finish pruning in the next couple of weeks (when the weather is forecast to be in the 70’s – 80’s in our area of southern California):
Summary of Proposed Sprays for Landscaping Roses:
| Column 1 |
Column 2 |
Column 3 |
Column 4 |
| Product |
Typical Rate (foliar) |
Minimum Spray Interval |
|
| Daconil WeatherStik 6F |
1.0–5.5 fl oz / 1,000 sq ft |
7–14 days after pruning through the Spring & Fall |
|
| Rally 40WSP |
Approx. 3–8 oz / 100 gal water |
~10–14 days |
|
| Quadris Flowable |
Equivalent to ~6–15.5 fl oz/acre scaled to coverage |
7–14 days |
|
| Indicate 5 |
Label-specific insect rate (oz/gal) |
Label-specified (often 7–14 days) |
|
| Maxicrop |
~1 oz product / gal water |
~7–14 days (foliar) |
|
What do you think of this approach with an initial frequency of every 14 days (given the blackspot pressure in our area) through the Spring? Once again, thanks so very much for your help! I really appreciate it and look forward to your further thoughts.
What do you think of this approach with an initial frequency of every 14 days through the Spring (given the blackspot pressure in our area already)? Once again, thanks so very much for your help! I truly value it, RoseJoy!
Every 14 days is fine if the disease pressure is not high, 10 days will be needed if disease pressure is high. I’m glad you are using Daconil Weather stik which is a warning signal versus danger. Daconil Ultrex can be used in hot weather but I wouldn’t use it because of the potential permanent eye damage. Just be cautious in hot weather.
Rally is a very good, I use Eagle. I’ve been very happy with the black spot control when combined with Mancozeb. I use Pro-stick T&O. Is this chemical available to you? It is better to use in the hot weather.
Using Quadris- Azoxystrobin will be very helpful when combined with the Myclobutanil when disease pressure is high. You wouldn’t use it every time you spray.
When you combine a systemic fungicide with a contact fungicide you minimize the risk of fungicide resistance.
You should be in good shape overall.