Right now you might be wondering if you have stumbled onto a immunology or fishkeeping webpage cleverly disguised as a rose page, but you might also see where this is all headed. The lesson to be learned from the common cold as it relates to rose culture is that we must either eliminate as much stress as possible from our roses or we must select roses which are less susceptible to blackspot. In All Things Is Important. For an in-depth treatise on this subject, click here. While we should not become zealots on this issue, we should try to minimize the amount of chemicals we apply to plants.
Chemicals have their place.
Dormant sprays, blackspot remedies, and selective insecticides should be part of the rose gardener's arsenal. In other words, let's use a marksman's rifle, not a shotgun, as our weapon. Surface-protectant sprays coat the leaf on the outside. Systemic fungicides penetrate to the interior of the leaf, interrupting the life-cycle of the fungus and preventing the spread of blackspot. There are two schools of thought on this subject.