Over the past few months I have been asked a lot of questions about a black mould on Camellia leaves.
This is quite a common problem and not just for Camellias. This mould looks like a smearing of soot, usually along the top of the plant’s leaves. Funnily enough this sooty looking mould is called Sooty Mould and is caused by aphids defecating.
Aphids love to dine on the juices inside your plant, they actually suck out the sugars made during photosynthesis. This sugary substance goes through the bugs and comes out the other end, being sweet and very sticky. The substance the aphids make is great for mould, which can then grow on your Camellia leaves, looking quite unsightly.
So now you know where it comes from, what can you do about it?
Well, the first thing to do is not to panic. Your Camellia will manage to live through this and I have never seen any badly damaged from the mould. So now you’ve calmed down, it would be a good idea to look at getting rid of the cause of the problem, which is the aphids.
The aphid is a scale insect; this little bug lives on the underside of the leaf and likes to stay along the rib. Ways to remove them depends on the size of your plant. If you have a fully grown Camellia this will be very difficult to treat because of its size. Treating on a small scale is much easier.
Organically you can first rub the little insects off. Finger and thumb is always a quick and easy way to remove pests. There are also natural predators you can buy such as hoverfly larvae and green lacewings. If you pop down to your nearest garden centre, they might be able to sell you some. The only problem with this sort of treatment is that outside the predators might go away before resolving the problem. The predators are also available by post, just search online.
If the pest has only decided to reside on a few branches, you might be able to remove and dispose of them and the aphid.
Chemical control is going to be difficult outside, especially on big plants. But if you do go down this path read up on what to use and take great care. Always thoroughly read chemical labels and spray responsibly. As scale insects are quite hard to kill with sprays, it would be best to spray at the end of June into July.
Now if you can’t do any of the above, don’t worry your plant should live through. As for the mould itself, soak with soapy water and then rub off. You won’t get it all off, but it will make the plant look better.
Most aphid poo – if not all, can cause sooty mould on plants, it’s not just a problem with Camellias. I’ve even seen sooty mould on a car underneath a lime tree, just please don’t take your plant through the car wash!