I have a yellow leaf holly bush in my garden and it is suffering with a black soot effect on the leaves on top and underneath. Could you tell me why this has happened and how I can sort this out?
Certified GKH Gardening Expert
The black residue is sooty mold, which is caused by the pests (usually aphids or mealy bugs). I would treat the plant with neem oil. It is effective against both of these bugs, as well as the sooty mold. Here is more information that may help you: https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm, https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm, https://www.gardeningknowhow.com/plant-problems/pests/mealybugs-white-residue-on-plants-leaves.htm, https://www.gardeningknowhow.com/plant-problems/pests/homemade-aphid-control-a-natural-way-to-kill-aphids.htm