Roses have black spots

Discussion in 'Trees, Shrubs and Roses' started by Don Perry, Apr 26, 2020.

  1. Don Perry

    Don Perry Seedling

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    I am just now getting interested in growing and maintaining my wife's roses. I have veggie gardened for several years, but not much interest in 'roses'. I bought my wife a Tropicana hybrid tea in a 2 gallon pot. I dug the hole twice as large as the pot and placed it in the hole, filled with potting soil and watered with Miracle Grow.
    I noticed that the bushes that are older than 2010 ( moved here then) have black spot on the leaves. One is some sort of small red rose with long shoots that probably need to be tied to a trellis. The other bush puts out a large red rose. (Mr. Lincoln ??) They are in the shade of a large red bud tree. I know they need full sun.
    How do I get rid of the black spot? I have fluffed the soil and added fertilizer. Weeded the bed, and pruned a few branches, but I'm sure I don't know what I'm doing.
     
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  3. Luis_pr

    Luis_pr New Seed

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    Oh, God. You cannot get rid of black spot. It is a fungal disease and the spores are all over. You can only hope to control it by making the environment hostile to the fungi, removing roses that are not resistant to BS and-or applying fungicides on a regular frequency. High humidity, shade and warm weather are things to look out for. Then again, sometimes the fungi is already there and the roses are not resistant so you get it no matter what.

    From the American Rose Society ( go here and click on "CLICK HERE TO VIEW .pdf"): https://www.rose.org/diseases

    "Cultural controls for black spot include sanitation (cleaning of defoliated debris in late winter, early spring), proper pruning to insure good air movement through the canopy, and watering so that the length of time foliage remains wet is reduced (Figure 9). Drip irrigation can also be used to reduce the length of time that foliage is wet.

    Resistance for black spot in modern rose cultivars is becoming more common since rose companies made black spot resistance a breeding priority. However, you must be cautious when a plant is claimed to be resistant. UT AgResearch tested over 200 cultivars for black spot resistance that had been marketed as disease resistant claims by rose companies. Only about 10 percent of the cultivars displayed acceptable levels of resistance in the multiyear study. Since that study’s completion more than a decade ago, some of the roses that were rated as resistant have failed in studies in other parts of the country. The most likely reason is the ability of the black spot pathogen to make genetic changes and perhaps differences in environmental conditions. There are many races of the black spot pathogen known to exist in the United States; the list of new strains of D. rosae keeps growing.In parts of the U.S. where black spot severity is high, fungicides may be required to successfully grow many cultivars of roses. These fungicides will be most effective if used preventatively. Since the pathogen is known to rapidly change genetically, it is important to rotate fungicides with different modes of action."

    Oklahoma State University suggests in https://extension.okstate.edu/fact-sheets/diseases-of-roses.html the following:

    Control
    1. Remove and destroy infected leaves during the season; remove infected twigs when pruning.
    2. Avoid overhead watering.
    3. Plant roses in an area with good soil drainage and ventilation. Avoid shady spots and dense plantings.
    4. Prune out old and diseased canes in the fall or winter.
    5. Mulch soil around plants and improve pH if necessary (see Extension Fact Sheet HLA-6403, “Roses in Oklahoma”).
    6. If one wishes to not have to spray for black spot and powdery mildew control, a few resistant cultivars are shown in Table 1. Other cultivars may be available at the local nursery. Disease resistance may be displayed on the plant tag or ask a nursery professional.
    7. For chemical control on disease-susceptible cultivars, use fungicides listed in the current circular E-832, Extension Agents’ Handbook of Insect, Plant Disease, and Weed Control. It is important that weekly fungicide applications begin with new growth in the spring and continue until frost in the fall. Sprays may be omitted during hot, dry periods in the summer. Many general purpose rose dusts and sprays are available that contain compatible materials for control not only of black spot and powdery mildew, but also for common insect pests.
    8. https://www.gardenguides.com/107208-organic-treatment-black-spots-roses.html
    9. I added number 8 -above- but could not stop my comment from appearing as i it came from OSU. The gardenstew editor just would not begin a new paragraph. So that link to gardenguides is mine
     
    Last edited: Apr 26, 2020
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  4. mart

    mart Hardy Maple

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    Roses are full sun ! You will probably just have to deal with it ! Unless you want to move them and no guarantee that will help ! Should not affect blooms !
     
  5. Dirtmechanic

    Dirtmechanic In Flower

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  6. Odif

    Odif Young Pine

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    Full sun.
     
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  7. Don Perry

    Don Perry Seedling

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    I thank all of you wonderful people ! you have given such good and professional advice. I'll try to relocate in a better place or buy resistant varieties.
     
  8. Cayuga Morning

    Cayuga Morning Strong Ash Plants Contributor

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    The roses I plant are shrub roses and very hardy. I like the The Meiggili Drift series. They seem to resist black spot very well. They can also handle less than full sun. I have Rosa Meiggili Peach Drift which has flowers that range from peachy pink to peachy yellow. Very pretty. I put compost around them in the spring and that's it. No fungicides, insecticides etc. I gave one to a friend and it is performing equally well for her.

    Another good shrub roses is The Fairy. Very hardy. Little care. Small pink flowers.

    I know everyone likes the Knockout roses but they have not done at all well for me. I don't have enough sun.

    A climber that I can recommend is Rosa Zephirine Drouhin. It is as old as the hills (1800's?), relatively thornless, can tolerate 1/2 day sun & still bloom and (at least in my yard) is not bothered by black spot. I love it. I fertilize it and that's it.

    @Luis_pr thank you for your posting about how to deal with black spot. Very comprehensive.
     
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  9. Odif

    Odif Young Pine

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    This rose was in complete shade last year. It had black spot and white powdery mildew. We moved it to full sunshine and now perfect healthy plant.
    83CC835C-B0A2-47C7-A6C8-8963545A86C4.jpeg
     
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  10. Dirtmechanic

    Dirtmechanic In Flower

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    Just gotta pop back in here about the 3336. It took 2 or 3 treatments but I have not seen black spot in several years now on the red cascade. It could be a useful tool.
     
  11. Don Perry

    Don Perry Seedling

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    Thanks for all your comments. I found an article that states I should remove all effected leaves and prune back any effected stems in the fall. I found no fungicide at Home Depot(next to worthless) I'm going to go to a very savvy gardener I know in the next town over. She has beautiful roses for sale and a beautiful rose garden also.
     
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