Anyone know roses? Yellow leaves--black spots..

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greybeard
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Anyone know roses? Yellow leaves--black spots..

Postby greybeard » Sat Aug 18, 2012 9:30 pm

Then, the leaves fall off. I figured a disease, maybe fungus but not sure. I'm not on my computer right now, so I can't post a picture, but they get plenty of water and Miracle gro.
Knockouts and herlooms affected, but they are right next to each other.

I got some fungicide today, but looks like it is just sulphur you mix with water.
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Re: Anyone know roses? Yellow leaves--black spots..

Postby Jogeephus » Sat Aug 18, 2012 9:31 pm

Blackspot. Its a fungus.
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Re: Anyone know roses? Yellow leaves--black spots..

Postby Jogeephus » Sat Aug 18, 2012 9:34 pm

Knockouts whould really have much trouble with blackspot though. :???:
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Re: Anyone know roses? Yellow leaves--black spots..

Postby CottageFarm » Sat Aug 18, 2012 10:05 pm

Hard to say without pics, but...

I would guess you've got at least 2 different things going on....

I agree Black spots & yellow leaves sounds fungal (either big concentric circles or small fuzzy spots)
however, small black spots, yellow leaves and leaf drop also sounds like too much water.

I would saturate with the fungicide, back off on water, and side dress with bone meal.
Also cut back the nitrogen for a while.
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Re: Anyone know roses? Yellow leaves--black spots..

Postby greybeard » Sat Aug 18, 2012 11:42 pm

I suppose it could be too much water, but it just started recently, and we had a heck of a wet 1st 1/2 of July.
Bone meal--you thinking a problem with calcium uptake?
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Re: Anyone know roses? Yellow leaves--black spots..

Postby CottageFarm » Sun Aug 19, 2012 9:43 am

No, not really calcium. Just increased phosphorus. Increasing phosphorus and decreasing nitrogen can help stressed plants during bloom.
How dry does the soil get between waterings. How do you water? Drip, overhead, hand water?

I still lean toward Black spot, as Jo mentioned. Do the canes show any signs of disease? Blossoms?
I forgot to mention to remove and destroy any diseased leaves (& canes). If it's blackspot, it's fungal, and contact with diseased leaves, as well as water splash from diseased leaves, weeds etc, will spread the disease further. Then saturate with fungicide. Apply late in day or on an overcast day. Not under high sun as it will stress the plant even more.

edit: Try these pics, does it look like what you're dealing with?
http://www.aragriculture.com/diseases/image_library/tree_ornamental/rose/black_spot.htm
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Re: Anyone know roses? Yellow leaves--black spots..

Postby Australian » Mon Oct 22, 2012 4:01 pm

I have 225 roses in my garden. I have hybrid teas,standards,floribundas,climbers and David Austins. The best roses for black spot are David Austins. Though there are lots of others now that have black spot resistance. I keep the fertilizer up to them, use a lot of sea weed based liquid fertilizer. If I get aphids I just spray with a pyrethrin based natural spray or I have used soapy water which seems to work as well. My roses are all just starting to bloom. Knowing when and how to prune also helps. This is the first year that I have been severe with my pruning of my David Austins and it has done them well. They were getting a bit rank because I had been only pruning them by a 1/3 each year over the past 10 years that I have had them.Its mid Spring here in Australia.
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