Curing Your Sooty Looking Plants

Do you remember the song from Mary Poppins about chimney sweeping adventures in early 20th century London? You may have come across plants that look like they’ve been blasted by a “chim-chimmeny” and this is a sure sign of the fungus commonly known as “sooty mold.”
It’s hard to bear looking at a plant that appears to have suffered from an industrial revolution. Furthermore, left unattended for even a little while, an outbreak can spread and quickly ruin a whole garden. Technically, sooty mold is just a cosmetic problem as it rarely if ever kills plants directly but rather just deprives them of their full potential to absorb sunlight. But for most gardens, aesthetics is everything—so take the mindset of vigilance and instant action!
Early detection is key to preventing a localized outbreak of sooty mold from becoming a garden wide blight. If you’re lucky enough to have a gardener, instruct him or her on what sooty mold is and what to look for, otherwise, stay on top of it yourself with thorough inspections at least on a weekly basis.
When you see sooty mold on a plant, trim the affected area(s) aggressively. Some plants cannot be saved once they have sooty mold and are best removed entirely to be replaced with a new plant when you are able. To be extra sure that the chance of spreading in your garden is minimized, you can discard your refuse in plastic bags sent to the trash and can wash or even sterilize your pruners and/or gardening gloves. At some point there’s a line between proper prevention and paranoia, but that’s for you to work out!
I’ve heard others recommend sooty mold removal by washing and scrubbing affected surfaces in soapy water, but for me, that isn’t aggressive enough. I would much rather wait for a severely trimmed plant to recover or a new plant to grow in replacement than see a sooty mold infestation go from a controllable situation than something beyond salvaging. A huge infestation in which an entire garden has been attacked might be an invitation for a whole new landscape to be created. Keep that in mind when tempted to take the light handed approach.
Another concern regarding sooty mold is controlling insect infestations that precipitate an outbreak. Aphids, mealybugs, whiteflies, and scale insects are the prime culprits for inducing sooty mold infestations. These insects all specialize in consuming plant sap. Their resulting secretions, known as honeydew, are rich in sugar and provide the perfect food for sooty mold. And let’s not confuse this term honeydew with the melon. We’re talking about a fine dew-like substance that is usually sticky upon touch from all that under-processed plant sugar.
Getting up close and inspecting your plants with a loupe will usually reveal the menacing party. If you’d rather someone else try to ID the pest for you, macrophotography may be another option. The absolute worst way to ID plant pests and pathogens are to bring an infected leaf or branch to someone’s garden and ask for their help. That’s actually a good way to incite the very person you are hoping to provide you with a friendly answer—as you’ve just exposed their plants to something they may have already worked very hard to eliminate or avoid.
As far as controlling the insects themselves, a great safe organic approach is with formulations of neem oil. Other synthetic insecticides are available but may not be recommended, especially if you harvest fruits and vegetables from your garden.
So lots of happy sooty mold sweeping to you. As the Mary Poppins song says, “A sweep is as lucky as lucky can be.”