Black Spot on Yuletide Camellia

Asked May 4, 2020, 2:47 PM EDT

We have a Camellia sasanqua that we planted last winter. Recently many of the leaves have developed black spots. I have examine the leaves at 10X and did not see any insects or spore structures. No mealy bugs, aphids or spider mites. The black spots are internal to the leaf, no surface mold. I am at a lost what it could be. We have a different variety of Camellia nearby that has no problem. I have attached photos of top and underside of leaf. The white material under the leaf is not webbing or mycelia, rather it's the cuticle peeling off. I considered oedema, the soil can be wet, but this looks nothing like the online pictures of oedema. Actually, it looks a lot like black spot of roses. I would appreciate any help you can provide. Thanks, Bruce

Marion County Oregon

1 Response

Dear Bruce,
Hi and thanks for contacting Ask an Expert.
This looks like black spot, a fungal disease that as you mentioned, attacks roses.There are a few things to do before spraying. You have good airflow at this time, and it needs to stay open to allow it to continue. Make sure the soil is draining and the plant roots are not sitting in water. Then remove and clean up any fallen leaves. Remove the mulch and put new mulch in as the fungus does live in the soil as well. You can spread the mulch out in an area that will dry it out as our rainy season comes to an end if you wish. I would not use it around any other plants though, maybe in a walkway.
The leaves should be put in the garbage and NOT composted as the fungus can live if the pile does not get very hot.
I have listed below a number of fungicides you could try. All of them are in garden stores. With one exception, I would not buy the Neem oil preparations as they often contain other sometimes more toxic ingredients. Buy pure Neem oil online. You will use a teaspoon to one gallon of water. This is good for insects pests (but it kills anything it touches) as well as a good fungicide. Spray bottom and tops of leaves.
Copper, Lime Sulfur, Neem oil, Potassium bicarbonate, Sulfur Dust, Wettable Sulfur.
These are all approved for organic use. Please read the instructions and follow them. If you use sulfur, you must wait 10 days to use another type of fungicide. It is a good idea to use two different kinds, they work differently and will be a better remedy for your camellia bush.
I have attached a link from the American Camellia Society for your review: https://www.americancamellias.com/care-culture-resources/insects-and-diseases. If you have any further questions please re-contact us.