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Black spots on leaves

Posted by Joopster 5 (Chicago) (My Page) on
Mon, Nov 4, 13 at 10:20

I planted some roses 2 months ago. I spotted some black spots on their leaves. Do I need to spray the leaves so late into the season or just let them be?

Also, the roses are still in blooming. How do I stop this? We went thru couple of nights of freeze but now it warming up to the high 50s again.

This post was edited by Joopster on Mon, Nov 4, 13 at 10:23


Follow-Up Postings:

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RE: Black spots on leaves

This is my first year growing roses, but I'll tell you what I've learned so far:

You should spray the entire plant, including the canes with a fungicide to kill the black spot. Rosemania.com has a product called Honor Guard (preventative)plus you'll need something to kill the fungus (mancozeb). You will also need a garden sprayer to mix the products in with water. After all the leaves have dropped off due to the cold weather, spray the ground around the plant because the black spot fungus will overwinter. You will need to start spraying them again in the spring when the leaves start growing.

It sounds like our weather is the same - frosts at night and 50's during the day. We still have roses on our bushes also, but no new buds have been forming since the past few weeks.

Hope this helps...


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RE: Black spots on leaves

This time of year, I just let the plants be. Even my "disease resistant" varieties get some spotting this late in the season. No additional fungicide sprays until I prune next spring. And no fungicide spray will "erase" the existing spots.

You can't stop them from blooming! Some years, they will continue until a very hard freeze. Enjoy the blooms, they will stop when it is time.


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RE: Black spots on leaves

Do you remember the names of your roses? You may or may not need to spray next spring -- forum members in Chicago can give suggestions if they know the varieties.


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RE: Black spots on leaves

Thanks all.

@ cecily, yes, they are Chicago Peace, Love and Peace, and David Austin's Port Sunlight. Love and Peace and Port Sunlight still in bloom but leaves are turning yellow with black spots. Chicago Peace stop blooming but the leaves are in healthy green with no spot.


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RE: Black spots on leaves

'Chicago Peace' is also susceptible to blackspot disease and will probably develop it next year. If you don't want to spray fungicide regularly, there are some resistant varieties. If you do spray, I use Bayer Advanced Disease Control for Roses, Flowers, and Shrubs (that exact name), which is preventative and curative. Get it online or maybe at Lowe's. It works well at two-week intervals.

You can't stop them from blooming and shouldn't try. The new growth will freeze soon anyway. In zone 5, most of the canes will be injured by winter. Go out and locate the graft swelling where the canes diverge. It should be buried to prevent winter damage. If the graft survives, the rose will grow back. If you haven't planted deep enough, you can replant during dormancy or pile soil over the graft once temperatures below 10 degrees impend.


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RE: Black spots on leaves

From the roses selected, I will make the assumption that you are not an experienced rose grower. If this assumption is correct, you may find it beneficial to do some reading about the potential dangers from the use of the mancozeb and of the Bayer product.

http://forums2.gardenweb.com/forums/load/roses/msg0517553020218.html

Here is a link that might be useful: link to earlier thread


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RE: Black spots on leaves

I'm very new at growing roses. This is my first house. I would like to learn more since I'm planing to add some more David Austin's next spring.


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RE: Black spots on leaves

Ask here about Austin roses that may be more disease resistant in your climate. Blackspot is the main disease to be concerned about. Roses that are described by somebody as "disease resistant" may not be resistant to blackspot.


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RE: Black spots on leaves

  • Posted by seil z6b MI (My Page) on
    Mon, Nov 4, 13 at 23:33

Black spot is pretty normal for this time of year in colder zones. The cooler damp weather is the perfect conditions for it. Besides that the roses are slowing down some because it is cooler and there is less light for photosynthesis. So their immune systems aren't as able to fight it off. I wouldn't bother to spray them now. Wait until the early spring when the roses are waking up.

You can not force the roses to go dormant. Only when the soil temperatures get cold enough will the plant go into dormancy. With the changeable weather conditions we've been having that could be any time from October to December. Don't worry about them continuing to grow and bloom. They'll be fine. Don't prune them back now. Just let them grow and stop dead heading them. You'll lose that new growth over the winter but you want to leave as much cane as possible to start with next spring. Roses store energy in the canes to come back with next year.

You've picked some very beautiful roses!


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RE: Black spots on leaves

Can I just remove the all the leaves now. Will it harm the rose?


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RE: Black spots on leaves

  • Posted by seil z6b MI (My Page) on
    Tue, Nov 5, 13 at 9:35

As long as there is green on the leaves they are still able to feed the rose so if you pick off leaves don't take the green ones. Usually once the leaf stops feeding the plant it falls off on it's own.


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RE: Black spots on leaves

Windy City gardening! Whoosh!


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RE: Black spots on leaves

  • Posted by seil z6b MI (My Page) on
    Wed, Nov 6, 13 at 18:57

Lol, Susan, that's a good way to look at it! I usually let winter take care of most of my leaves. Between the wind and early spring pruning I rarely have any left to pick off.


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RE: Black spots on leaves

All a plant's energy for growth comes from green leaves in the sunshine. Some of this energy is stored for regrowth in the spring. Any leaves that are still functioning are performing a valuable service and should be left alone until the plant shuts down for winter.


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