I have a Double Delight rose that has had persistant problems with black spot, powdery mildew, and I'm guessing rust. The leaves turn yellow and fall off, but still seems to bloom okay. By the way, I live in Knoxville, TN if that helps. I have a Knockout planted right next to it, and it looks healthy as a horse. I've been spraying it with Orthenex every 7-10 days as instructed by the label and the problem persists. I used to grow Double Delights down in Florida and they were always the showcase of my roses, but I don't seem to have the same luck here in eastern Tennessee. Any ideas of what I'm doing wrong or suggestions would be much appreciated.
Sometimes we get a rosebush or rosebushes with the same name but their performance is just not like ones we have had before. I usually give those about three years to get established and get with it. If they do not, out they go. Since the Knockout rosebush is doing well I would say it is more the rosebush than anything you are doing. The Orthenex may not be something the bush likes though and it could be making it sickly. I recommend using a product called Green Cure for your fungicide and if you absolutely have to spray for bugs try using the Bayer Advanced insect killer. I have heard of some folks having problems with some rosebushes when using Orthenex. It is a great product just some rosebushes are sensitive to it. If the Double Delight you have is an older bush, I would say to take it out, amend the soils well and plant a new one and see how it does. Check the pH of your soils in that specific area as well, just in case there is something out of whack with the soils right there.