I have very large elderly camellias in my garden which have been a delight for many years. Three plants growing next to each other are are about 10 feet tall and 8 feet wide. The foliage on two of them is completely covered with a deposit which looks like soot. My local plant center tells me to wipe this off each leaf - totally impossible with such mature shrubs! Can you suggest any treatment or will I have to get someone to dig them out and dispose of them? I do not want this problem to spread to other camellias, especially the ones which I grew from seed.
Certified GKH Gardening Expert
This is called sooty mold, which more often than not is brought about by some type of pest, like aphid or mealy bug. I would recommend neem oil. We have found it to be very effective against these kinds of pests and will also help treat the sooty mold. These articles will explain more: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm, https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm