Roses forum: Please help find out what's wrong with this rose

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zolotoy
Jul 4, 2016 5:41 AM CST
This is a double knockout rose. Please help me to figure out what's wrong with it.
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[Last edited by zolotoy - Jul 4, 2016 5:42 AM (+)]
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Name: Larry
Enterprise, Al. 36330 (Zone 8b)
Region: Alabama Composter Garden Photography Garden Ideas: Master Level Plant Identifier Celebrating Gardening: 2015
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Seedfork
Jul 4, 2016 10:30 AM CST
zolotoy, Welcome!
Nice to have you here and I am sure someone will have some suggestions for you. It would be a big help to know your location, that could help determine what type of insects are in the region that could be causing the damage, if it is indeed insect damage!
Name: Zuzu
Northern California (Zone 9a)
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zuzu
Jul 4, 2016 11:20 AM CST

Moderator

Welcome to NGA, Zolotoy.

That is the damage caused by sawfly larvae, commonly known as rose slugs. They hide out on the underside of the leaves and resemble small caterpillars. I woukl think that the season for them is over or almost over whatever your location might be, so those leaves soon will be replaced by nice new ones.
Name: Andi
Pocono Mountains, PA (Zone 6a)
Charter ATP Member I helped beta test the first seed swap
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GardenQuilts
Jul 5, 2016 2:50 PM CST
Could be gypsy moth catipillars too. I am having problems with them here.

In cooler weather you could use neems oil spray, but it will burn the leaves in summer heat. Try hitting the plants with water from the garden hose first thing in the morning. The leaves need to dry else you will get black spot.

If you use chemicals in your garden, you can try Bayer 3in1 systemic rose care granules at half strength. Water the plants well before applying and afterwards for a few days. I like to treat before a rain storm.

You could also cut the damaged leaves off the plant ..... Don't compost them.

zolotoy
Jul 5, 2016 4:48 PM CST
I am in Chicago area.
Name: Cindi
Wichita, Kansas (Zone 7a)
Charter ATP Member Plant and/or Seed Trader Permaculture Roses Ponds Peonies
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CindiKS
Jul 5, 2016 5:47 PM CST
Those insects have most likely finished their job, so my opinion is, no chemicals are necessary. While the leaves don't look beautiful, the plant still needs those leaves. The new ones will be pretty again, and the holey ones won't be quite so obvious.
If a plant has diseased leaves, it's a different situation. Those, you pull off and discard and let the plant struggle with the deficit of leaf matter, which is the lesser of the two problems.
Remember that children, marriages, and flower gardens reflect the kind of care they get.
H. Jackson Brown, Jr.

zolotoy
Jul 6, 2016 3:57 AM CST
What do you mean by diseased leaves?
Name: Cindi
Wichita, Kansas (Zone 7a)
Charter ATP Member Plant and/or Seed Trader Permaculture Roses Ponds Peonies
Lilies Irises Daylilies Dog Lover Beekeeper Garden Ideas: Master Level
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CindiKS
Jul 6, 2016 10:14 AM CST
Zolotoy, your rose doesn't appear to have any diseased leaves, and probably won't get disease because the Knock Out roses are very disease resistant in most parts of the country. Thumbs up
Common diseases are black spot, mildew, and rust. Knock Outs were specifically bred for gardeners who insisted on plants that don't need chemicals to look good. They led the way for many more rose introductions that are even more disease resistant. So far, though, there isn't a rose that is "insect resistant".
Beneficial insects do a good job of keeping most bad insects in check, along with vigilance from the gardener in catching infestations early. My flowers have insects, but preying mantis, ladybugs, wasps, birds, and frogs do a good job keeping everything in balance. If I were to use any insecticide, I would kill off these beneficial insects along with the intended victim, and that could create bigger problems in the long run. I've never had a rose with as much damage as yours has, so I suspect your beneficial insects were missing, allowing sawfly to multiply unchecked.
Another way to keep disease and insect pressure down is to leave some space between plants so there is good air movement, and to plant something other than roses in the same area. I keep a good mulch layer under the roses if I don't have a low growing plant there. Some people keep the ground bare, though, so they can keep the area clear of fallen leaves and hiding insects. You have to experiment and see what works best in your garden. It's crazy. Some years a technique works, other years it doesn't. Shrug!
Remember that children, marriages, and flower gardens reflect the kind of care they get.
H. Jackson Brown, Jr.

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