best preventive option in my rose bed for black spot and other diseases

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KD

best preventive option in my rose bed for black spot and other diseases

by

Karen DeCoster

7 years ago

6

I got hit hard with black spot later this year and was unable to remove every diseased leaf, hence many worked their way into the mulch. I understand that I have options regarding how to prevent the spores now living in the mulch from spreading to new growth in spring: 1. remove all mulch now 2. wait until spring 3. bury the contaminated mulch in a thick layer or soil or more mulch. PS If option 1, can I use that mulch around evergreens or must I burn/dispose of it?

Andy McIndoe · Answer 1 · 6th November 2016, 07:41:48

Hi Karen Its virtually impossible to prevent a few diseased leaves from getting into the mulch around your roses. Don't panic. You are right about raking it away and cleaning up the ground. You could use it around other evergreen shrubs and hedges that are away from the roses. Covering the ground with a layer of inexpensive growing medium helps. I would put on a generous application of rose fertiliser, then the growing medium. But first, remove all the foliage and give them a good winter prune - you may do this in early spring instead depending on where you live. There are always bad blackspot years and then better seasons.

Karen DeCoster · Answer 2 · 7th November 2016, 01:32:42

Thank you so much, Andy!! To be clear, are you saying that I: 1. remove any remaining diseased foliage in spring? 2. rake up diseased foliage that fell to ground in spring? 3. Winter prune in spring? 4. fertilize and add layer of compost or good top soil in spring? Any benefit to doing one or more step above now rather than later? Karen

Michael Marriott · Answer 3 · 21st November 2016, 10:05:32

Hello Karen, I'm sorry I couldn't reply sooner I've been on holiday. Andy's advice is very good although I always think that once diseased leaves get into the mulch there is little chance of the spores getting back onto next season's young leaves especially if you cover them with a fresh layer of mulch. the sores are very likely to rot down very quickly. the most likely place for the spores to overwinter are on the older stems which is why cutting out dead, diseased and old stems is so important and of course plucking off any leaves that are still on the plant at pruning time or now. if you remove too many leaves during the growing season you are likely to weaken the plant as it wont be able to photosynthesize and so you it will make it more susceptible to disease. a more radical approach if the rose regularly gets bad blackspot is to dig t up and replace it with a variety that is naturally more resistant to disease. how old is the rose? Michael

Karen DeCoster · Answer 4 · 21st November 2016, 14:00:51

THANK YOU, Michael! Re: diseased stems, I must confess ignorance here: I thought black spot only affected the leaves. Is it easy to distinguished stems that have it from those that don't? Am I better off pruning now or can it wait until early spring? What about spraying stems with sulphur spray? The roses (4 got hit hard and nearly all had a little I think due to proximity) are 2-3 years old? With gratitude, Karen PS do you have a class on proper pruning methods for different species?

Michael Marriott · Answer 5 · 21st November 2016, 14:11:55

Yes you're right Karen it only effects the leaves but the spores can easily overwinter on the stems especially if they are older ones. At 2-3 years old that shouldn't be too much of a problem yet You can spray with Sulphur but I must say I never like using that as I'm worried it will lead to an imbalance in the soil. as to pruning it depends where you are in the States. I do run a course for pruning in January but over here at the nursery in the UK

Karen DeCoster · Answer 6 · 21st November 2016, 20:01:41

Oh dear, I have used sulphur spray for 3 years 3x/year. Can I test to determine the affect its had on the soil? I live in New England, in the state of Massachusetts.

best preventive option in my rose bed for black spot and other diseases

best preventive option in my rose bed for black spot and other diseases

Karen DeCoster

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