I have two plants, a phlox and a coneflower, planted very near each other. Both are suffering from a similar plight, though I don't know what it is. The phlox is established, but the coneflower is new this spring. Each has a section/stalk that has turned completely black. What could be causing this, and what do I do about it?
Certified GKH Gardening Expert
Is the black soot-like? This could be sooty mold fungus, which is brought about through insect pests. Treating the plants with Neem oil should help with both the sooty mold and any pests that are contributing to the issue. Even if it's another type of fungal problem, Neem oil should still be effective. Here is more information: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm