Q.What causes my rose bush to look sickly?
This is a “Double Delight” “knock-out” Rose bush. I have tried several sprays and organic treatments, but every year it looks like photo. I planted the rose bush 3 years ago. I have even dug it up , put fresh soil and replanted it. Nothing seems to work
It looks heathy except for the insect damage. Rose slugs have been bad in a lot of places this year. They are spring feeders, the larval stage of the sawfly, and look like tiny green worms on the underside of leaves. Where they have fed looks like gray lace that eventually gives way to a hole. In the south, there may be a second generation a few months after the first. To work, sprays need to be rated for these pests and sprayed on the top and bottom of leaves when the larvae are present. The other common rose pest is Japanese beetles; they are voracious eaters of rose leaves. They can be removed with a small hand vac or flicked into a pail of soapy water. Spraying after the pest has damaged leaves will not correct the problem. Vigilance is the key. Sawfly damage starts at the bottom leaves whereas Japanese beetles start eat leaves and rose buds on the outside of the bush. Links to more information follow.
https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-slugs.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/japanese-beetles-roses.htm