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Black spot

angelawendy21angelawendy21 Posts: 9
in Problem solving
Black spot has been a problem for all the rose bushes in my mixed hybrid tea rose-bed for the last three or four years but this year it has been so much worse.  One of the roses, Polar Star, has now lost all its leaves and another, Freedom, has lost about half of them.  Other bushes are all affected to some degree.  I have sprayed with Fungus Clear Ultra numerous times as per instructions on the box at 21 day intervals from when it first appeared, but this doesn't seem to have prevented the problem.  I am seriously considering removing all the bushes and growing something else next summer unless I can deal with the problem.  The new rose bushes were all planted in the bed five years ago.
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  • edhelkaedhelka Posts: 2,351
    This was a really bad year for blackspot.
    For most varieties, the susceptibility to it is genetic and you can't do much with it if you already spray. Here are some tips that could possibly help but probably won't help completely:
    - Make sure the roses are completely happy - have enough water and nutrients. Potassium, magnesium and calcium can help with diseases, depending on your soil, you can use tomato food or liquid seaweed to supplement these.
    - Water in the morning to the base of the plants, not in the evening and no sprinklers/overhead watering.
    - Remove all diseased leaves, both on the plants and fallen.
    - Make air circulation as good as possible, no perennials too close and prune for air circulation.
    - Alternate two or three different anti-fungal products. Your local blackspot spores can become resistant to the product you use.
    - Use dormant spray in winter (sulphur or other product for the dormancy season). Remove all fallen leaves and mulch with a thick layer of composted manure.
    If these won't help and you can't tolerate the look of your roses, grow very disease resistant varieties only. But don't plant any new roses where old roses were (not without removing/changing at least part of the soil) because of the rose replant disease.
  • angelawendy21angelawendy21 Posts: 9
    Thank you for such helpful suggestions.  I will try for one more season and see how I get on!  If I do decide to get a few black-spot resistant hybrid teas, can you or anyone else give me a few suggestions please?
  • BijdezeeBijdezee Posts: 1,484
    Even my normally healthy hybrid tea rose succumbed to it this year. I'm clearing up any fallen leaves then I will cut it back by half after the leaves are all off. I do this in autumn because of wind rock. Then I will spread a good mulch down and hope for better next year. Might start earlier with the black spot spray. Prefer not to but seems I need to get this u der control. 
  • FireFire Posts: 19,096
    I've had a bad year too.
  • edhelkaedhelka Posts: 2,351
    @angelawendy21 I don't grow many hybrid teas, at least not the traditional high-centred ones. My most disease resistant roses are floribundas and shrubs.
    You can try to ask for recommendations in our Rose Season 2020 thread.
  • PosyPosy Posts: 3,601
    There is a product called something like Sulphur rose. It really helps. I also found that feeding with a product for acid lovers helped roses to take up nutrients from my slightly alkaline soil.
  • angelawendy21angelawendy21 Posts: 9
    Many thanks to everyone for helpful advice and comments.  I will certainly try some of them soon.
  • BobTheGardenerBobTheGardener Posts: 11,385
    When you cut them back in spring, it might be worth cutting back the most affected ones a bit harder than you normally would, and certainly remove any weaker growth.  This will encourage strong new growth which may prove more resistant.  If it gets decimated again, I would replace it with a known resistant variety (or something else completely, which is my usual preference.)
    A trowel in the hand is worth a thousand lost under a bush.
  • jamesholtjamesholt Posts: 593
    Can someone tell me how often to spray for black spot
  • Cambridgerose12Cambridgerose12 Posts: 1,134
    I did use to spray, but I found that I simply couldn't keep on top of the disease.  So I've been trying for many years to grow roses without any spraying, and building up some information on which are the most disease-resistant types in my area (East of England). I'm afraid I have less info about hybrid teas and floribundas as I tend to prefer shrub roses, precisely because they are often less prone to fungal diseases. The best piece of advice I'd have, besides @edhelka's excellent and complete recommendations, is to visit rose gardens in the height of the flowering season. While commercial nurserymen are allowed stronger nastier chemicals than we can use at home, if a rose is particularly susceptible it will still show symptoms. So, if you go and take down the names of the varieties that are glowing with health, that's a good start.

    FWIW: I have found the Hybrid Tea 'Deep Secret' and some floribundas--'Radox Bouquet', 'For Your Eyes Only'--to be good, also many of the Hybrid Musks, such as 'Felicia' and 'Cornelia'. Rugosa roses never get it, nor do many of the Old Roses. There are others. Some David Austin roses are pretty healthy, e.g. 'Mary Rose' or 'Susan Williams-Ellis', 'Harlow Carr', also Peter Beales roses such as 'St. Ethelburga'.
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