Double knockout roses doing poorly Help!

tbug45(8a)May 7, 2008

Hello group! I planted 5 double KO rose bushes in April 07,

they did wonderful! I cut them back in Feb.08 they were doing great and produced many buds in March but..they were covered with aphids I treated with organic pesticide which did not touch them so I treated with a systemic pesticide,after two treatments the aphids seemed to be under control within a week (this was two weeks ago) the leaves started turning yellow with brown spots and falling off so i treated with a systemic fungicide there is new growth on only two plants, my question is should I go ahead and cut them back again? as you can imagine they look awful I would send a picture but I cannot figure out how to do that. Thanks Debbie

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cecily(7 VA)

Hi Debbie, where do you live? How's the weather (heat)? What are the names of the specific products that you used? How much rain have you had in the past couple of weeks and have you watered also?

    Bookmark   May 7, 2008 at 12:42PM
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Hi Cecily, I live in central Texas we have been dry here until the last few weeks we have had about 3 " of rain the weather has been in the 70's to low 80's I used ortho systemic insect killer that controls insects and mites and ferti-lome systemic fungicide,they both state that they can be used on roses I usually water deeply every few weeks more often in the summer not so much in the winter.

    Bookmark   May 7, 2008 at 1:05PM
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cecily(7 VA)

Hi again,
There are a couple of possible issues here. Spraying anything in warm, dry weather has the potential to burn foliage. Be sure to DEEP water the day before spraying anything or giving any sort of drench. Spray in the early morning or evening when the day is coolest. Spraying Neem or other 'organic' insecticides can also burn foliage in hot weather because they contain oils. Your roses will have aphids every spring. I promise! Spring = aphids. Aphids are best controlled by squishing (very satisfying to the gardener) or blasting with a strong stream of water from a garden hose (more effective). Treating aphids with insecticide is a mistake, it sets your roses up for infestation by spider mites and spider mites are MUCH more difficult to kill. Aphid damage is cosmetic, they don't really harm your bushes. Since you've already used pesticide, relax, you won't automatically have spider mites but for heaven's sake don't use any more pesticide on your roses.

I'm thinking that you used fungicide because yellowing leaves with spots sounds like blackspot. In central Texas you won't see BS on Knockout roses. Maybe some wimpy rose like Iceberg or Lagerfeld would BS in Texas but not Knockout. Your humidity level is too low and your summers are too hot. I think your roses defoliated due to spray burn.

How can you best help your poor naked roses? Water, water, water. Your roses should be deep watered twice a week to grow & bloom nicely. Any week that you receive two inches of rain, don't water. If it rains less than two inches a week in summer, water. If it rains less than an inch a week in fall, water. Water, water, water.

You have several chemical products formulated for roses in your garage and your Knockouts don't need them. Go to the garden center and buy a hybrid tea rose so you have a rose to nurture. You sound like a very nice person and you truly want to care for your roses but Knockout only needs water.

    Bookmark   May 7, 2008 at 2:02PM
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I agree. Knockouts never need to be sprayed with chemicals. However, they do appreciate periodic feedings with organic material and organic fertilizer. What shrub doesn't?

You most likely burned the leaves with too much chemical. Water them well, and keep them watered (but not overwatered). They should recover.


    Bookmark   May 8, 2008 at 11:55PM
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I bought 2 "red" double knockout bushes this spring. They had buds already from the nursery, so I planted them and have watered them as needed, when we don't get rain. I did have a ''rabbit'' problem, and I ended up just buying mesh covers and take them off during the day so the rabbits can't get to the bush. But, one bush, the rabbits ate down pretty well, but it is coming back GREAT with new 'red' leaves and new buds. The other didn't get eaten by rabbits at all (not sure why). It had about 16 roses on it but no new growth of leaves and it's a pretty small bush. I'd say about 10 to 11 inches high and 8 inches wide, but man, TONS of buds. I noticed the other bush (the ones the rabbits had eaten alot) has alot of new growth, so I cut off all but 2 of the roses on the other bush hoping to get NEW red leaves and in the end a larger bush. Is this OK to do, as I read it on some post, that others have done this as well.

They are FANTASTIC and BEAUTIFUL bushes. I love them. :)

Any help is greatly appreciated.

    Bookmark   May 31, 2008 at 9:44AM
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Knocking aphids off your rosebush with the water hose is useless because they just crawl backup on the bush. I tried this after reading about it. My infestation was complete, resorted to insecticide and as you stated the spider mites and black spot are killing my roses. I am thinking of just buying new plants and starting over but I will just have the same problem next year. So frustrating. I read to plant merigolds, and I did, but the aphids don't seem to mind them at all.

    Bookmark   May 24, 2011 at 6:17PM
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