Rose Blackspot in USDA Plant Hardiness Zone #10-A

Insects & Diseases
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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:

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As always, I welcome your thoughts and recommendations. Thanks tremendously for your help!

1 Like
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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.

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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

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“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.

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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!

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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.

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I am new to growing roses. I live in northern California. I am currently wondering about fungus prevention. Should I be considering a systemic fungicide or alternating two? Articles on options don’t seem to agree with each other. Does anyone have a great resource or have the knowledge themselves. Or should I stay away from the systemic type?

Thank you, Janet

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Welcome Jan,

What type of fungal diseases are you dealing with? What type of roses do you grow? What are you currently using?

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I’m wanting to know the best approach to prevention. I don’t know what I should be using. I have no fungus now, thankfully.
I’m using neem oil. Last year I used DrEarth
Organic anti fungal. I lost one rose to black spot. My roses are heirloom roses. Is there a resource you use that you have come to count on? Should I be considering using a systemic fungicide for prevention?
Thank you

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Black spot can be very difficult to control. I combine Mancozeb aka Manzate, aka Dithane, which is a contact fungicide, which helps, kill the fungal spores. I combine it with a systemic fungicide, e.g., Myclobutanil or Propiconazole or Tebuconazole. These fungicides are Preventative and will last 10 to 14 days within the leaves. These fungicides when combined together in the same spray tank will successfully control black spot. I don’t usually use the drenches.

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So you use a contact type and a systemic together? Is this preventative?

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Thank you. I get it. It’s making sense.

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Where are you getting the Manzate or equivalent?
Thanks, Jan

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Yes, I use both a contact ( to kill active black spot spores) and a systemic which is preventative. I will combine Myclobutanil with Manzate (aka Mancozeb). Sometimes if disease pressure is high (lots of rain). I will add Azoxystrobin. I will also rotate with Propiconazole which is the same chemical class as Myclobutanil. The key is to be consistent in spraying every 10 to 14 days.

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Thank you.
I can’t get Manciceb in California.
I can get Propiconuzole and Mycolbutani
Do you have experience with chlorthslonil?
Thank you for all of this good information.

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That is a problem about Mancozeb in Ca. Yes, you can use Daconil aka Chlorothalonil, however, when the temperatures are hotter it can damage rose leaves. Either by bronzing or blackening the leaves. Daconil Ultrex is less likely to do this, but you will need to wear goggles to protect your eyes. You also might try to alternate every three months with some type of Copper Fungicide, because copper can burn also. The systemic fungicides must be rotated with a different mode of action. If you use the same type over and over, black spot and other fungal diseases will become resistant to them and become ineffective. Please contact your closest rose society and get in touch with the ARS Consulting Rosarians. They may have some good suggestions for you.

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Thank you for al of this information.

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@Rosejoy Hi,

My husband and I have about 38 hybrid tea roses we have collected over the years. We were doing a spray program given to us by the rose store which we have followed for years until this year when we were restocking on chemicals. My husband called and asked why they no longer sale Captan. They told us it is a carcinogenic. We can order it from our local AG dealer but with us having a small farm and growing organically, I would like to have a less dangerous option but with the same affect, so selfish I know:) Also we are using mini pine bark nuggets but my husband seems to think this is a problem as well for harboring pest.

Spray Program:

Every 10 Days

  • Fungicide Prevention and Insecticide Prevention.

    • Add to 1 Gallon of H20:

      • 5 tsp Captan

      • 2 1/2 tsp Thiomyl

      • Bonide Systematic Insecticide

      • Spreader Sticker

Any help you could provide would be so wonderful, thank you so much:)

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Good afternoon Krystal,

What state do you live in? Mancozeb, Manzate or Dithane (all the same chemical) is a very effective contact fungicide in controlling black spot ( I buy the 6 pound bag). But it is restricted in several states.

Chlorothalonil is aka Daconil. Which is also an effective contact fungicide, but can damage rose leaves if the temperatures are above 80 degrees. I use it spring and fall (except right now it is 90 degrees in North West South Carolina). Daconil Ultrex is not as likely to burn rose leaves, but you do need to wear goggles when using it.

Thiomyl is a good systemic fungicide and is good to rotate with, but maximum effectiveness is about 7 days. You might be happier using Myclobutanil (Eagle) or Propiconazole (Honor Guard) and mix either with your contact fungicide.

I was talking to my local sales representative about Captan, He said it is now only available in huge sizes because there were so many environmental complaints about it.s

Since I take care of several larger rose gardens, I will rotate Myclobutanil with Manzate Pro Stick (aka Pentathlon) and in 10 to 14 days. Then I will rotate after 2 sprays to Propiconazole with the Manzate. If disease pressure is high (lots of rain) I will add the generic Azoxystrobin or sometimes I will use Pageant. I use a spreader stick like Indicate 5, which turns the water pink as it decreases the pH of the water.

I don’t typically use an insecticide unless I see an infestation of a specific insect. Unfortunately, since it gets so hot here, I do need to spray for two spotted spider mites as a preventative. I will use Floramite, Shuttle, Avid & Tetrasan, sometimes Akari.

You might want to take a look at two other less toxic things. Bonide sells Captain Jack’s Neem Max, my sales person said it is very effective and has a new spreader sticker that helps it stay effective on the leaves for at least a week. It mixes extremely well in water. Something to think about.

Also a new biofungicide know as Amlyoshield ( now marketed to home gardeners a Magic Gardener) is also a very good preventative for many fungal diseases. However, if you already have black spot or other fungal diseases you would need to get that under complete control first before using it.

Hope this helps.

Sheree (Rosejoy)

Someone mentioned you in a post.

| krystal-buenrostro
April 16 |

  • | - |

@Rosejoy Hi,

My husband and I have about 38 hybrid tea roses we have collected over the years. We were doing a spray program given to us by the rose store which we have followed for years until this year when we were restocking on chemicals. My husband called and asked why they no longer sale Captan. They told us it is a carcinogenic. We can order it from our local AG dealer but with us having a small farm and growing organically, I would like to have a less dangerous option but with the same affect, so selfish I know:) Also we are using mini pine bark nuggets but my husband seems to think this is a problem as well for harboring pest.

Spray Program:

Every 10 Days

  • Fungicide Prevention and Insecticide Prevention.

    • Add to 1 Gallon of H20:

      • 5 tsp Captan

      • 2 1/2 tsp Thiomyl

      • Bonide Systematic Insecticide

      • Spreader Sticker

Any help you could provide would be so wonderful, thank you so much:)

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Thank you so much Sheree! We are located in NC close to the SC line. Last question, what type of mulch or pine needle do you prefer? We have been using mini pine bark nuggets.