I'm pretty new at gardening outside the veggie patch, but have recently discovered some beautiful
plant life called
flowers! In fact, we bought a house, & a normal yard came with it... & in that yard there were 21
rose bushes (4 varieties)! All I can tell you about your
rose problems, is I've learned this year & what has worked for me.
I ran across a product called VF-11
plant Food, & this is what it says about
roses:
"You will be so pleased with the abundance
of blooms!! Foliar Feed your
roses once a week
Hose-end sprayer is ideal...one ounce VF-11 to a gallon water. Morning sun is ideal time to spray
roses. If you keep up this routine, on a weekly basis, you will have another lovely surprise.... no aphids and no mildew!!!! Let me explain why....VF-11 builds so much strength and health that
plant cells 'harden' and 'seal in' the amino acids which aphids feed on. You have merely eliminated their food supply. And you have done it without the use of poisonous systemic or pesticides. Pretty nice...huh? And mildew is eliminated because VF-11 changes the pH and creates a condition where mildew can not grow."
I tried this stuff, & LOVE IT! So far, everything it claims to do, IT HAS DONE!
I've used it on all my
roses for Black Spot, aphid & powdery mildew with success that I hadn't achieved with any other applications. I even accepted a potted
rose from a friend (like I NEED another
rose bush!
)& it had black spot BAD - nearly EVERY leaf! I almost stripped the bush bare; took it out of the pot (threw the dirt & the pot in the trash to be taken to the dump); ruthlessly washed the roots (thinking that I might shock it to death, but that's only 1 step away from black spot anyway, in my view!); sprayed the roots with undiluted VH-11 (It also claims to be a substitute for Root-Tone); & re-potted it. I sprayed & watered it with VF-11 (ONLY) for about 2 weeks, then sat back & watched it become the healthiest
rose bush I have!
I don't believe it makes sense to rely on ANY application to fight Black Spot without first stripping off EVERY infected leaf, AND thoroughly removing any fallen leaves/bark/twigs from under the bush! (I use my shop vac.) Otherwise, your time & money are about as effective as shoveling snow in a blizzard! Another thing I've learned about
rose bushes, as Mike57 mentioned, is that they do need good circulation throughout, so don't let them get too bushy in the middle. (Maybe you aren't supposed to, but I cut mine back where they start touching the house [keeps bugs outdoors where they belong] & when they start getting too full... They don't seem to mind the trim, at all!)