Black spot

Discussion in 'Rosa (roses)' started by MetalVixen, Aug 14, 2006.

  1. MetalVixen

    MetalVixen Member

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    SE PA
    Hi all, new here. I searched through for some black spot answers but nothing quite matched what I was looking for.

    I am a novice at this. Have one successful season under my belt. I bought several rose hedges from a mail order company and they did well last year. This year, it has been a wet, humid summer and black spot has taken over on several of my bushes. I have tried fungicides from the store to no avail. Some of my bushes have lost all of their lower leaves, leaving only the topmost leaves and blooms.

    My question is, can I save these bushes? I have switched back to a fungicide I used last year that worked excellent, and while this will help prevent further spread, Im not quite sure to do with my naked bushes. Should I trim them back and pray for the best?

    Id appreciate any help you can give.

    SE PA, USA
  2. Weekend Gardener

    Weekend Gardener Active Member 10 Years

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    Coquitlam, BC
    Once balck spot has taken hold, there isn't anything available in Canada that can "cure" the infection. I would just allow the rose bushes to defoliate. Very soon, new leaves and laterals will reappear. It is these new leaves that you need to focus your spray program on as most sprays work by preventing new leaves being infected. The frequency of the spraying is also important - read the instructions and follow carefully.

    I am not sure what fungicide you are using. The choice in Canada is highly limited. I have basically given up spraying and learnt to live with black spots. But seeing that you are in the USA, your options are much wider. You might want to talk to your local Rose Society, and get on to the website of the American Rose Society.

    Will your roses die? Generally not. Blackspots tend to hit later in the season, as they required warmer temperatures to cause infection. Most roses, therefore, have an opportunity to recover some vigour in the spring and early season, and again, in early fall. My David Austin, Eglantyne, has a tendency to become completely leaf less in some years, but it always bounces back. Just leave the roses alone - prune to tidy up if you must.

    Should you get rid of the roses? Not yet, if you have just planted them. My experience is that younger and weaker roses are more susceptible. Give it a year or two of good care. If they are still badly affected even when they have grown to be healthy full grown plants, then, perhaps it's time to think of other, more disease resistant roses.

    Some general measures may reduce the infection rate:
    1. Consider roses that are known to be more resistant - you will need to look around other people's "no spray" gardens to see which roses tend to be the cleanest. Our pink flower carpet rose, for example, does not get blackspot (but it's subject to powdery mildew under the right conditions)
    2. The spots of the fungus needs at least 4 hours of wetness to germinate. Minimise overhead watering. Or, if this is not avoidable, do so in the morning so that the leaves have a chance to dry up quickly.
    3. Keep the bushes and the soil clean - remove all of the infected leaves and other material.
    4. If you do spray, start early in the season, once the leaves start to unfurl, and keep up with the program. (I find this time consuming and now does not consider it to be worth the effort or money.)

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