Q&A - What is the black substance on my holly leaves?
Question:
The leaves of my holly plant are covered in a black substance. What is causing this and what can I do to save the plant?
Answer:
The black substance is sooty mold. It is a fungus, but don’t treat the fungus. The sooty mold is growing on honeydew that is secreted by insects that are feeding on the plant. To fix the problem you need to control the insects. You can use horticultural oils that will suffocate the insect or use a systemic insecticide like imidacloprid. Once the insects are no longer present the sooty mold will slowly wear off the leaves. If you want to speed the process you can wash off the leaves. If you can identify the insect you have, research the best time of year to control it.
Related Resources:
Sooty Mold (University of California)
Sooty Mold (University of Wisconsin)
Black, Sooty Mold on Landscape Plants
The leaves of my holly plant are covered in a black substance. What is causing this and what can I do to save the plant?
Answer:
The black substance is sooty mold. It is a fungus, but don’t treat the fungus. The sooty mold is growing on honeydew that is secreted by insects that are feeding on the plant. To fix the problem you need to control the insects. You can use horticultural oils that will suffocate the insect or use a systemic insecticide like imidacloprid. Once the insects are no longer present the sooty mold will slowly wear off the leaves. If you want to speed the process you can wash off the leaves. If you can identify the insect you have, research the best time of year to control it.
Related Resources:
Sooty Mold (University of California)
Sooty Mold (University of Wisconsin)
Black, Sooty Mold on Landscape Plants